George Eastman House, International Museum of Photography and Film
Image Permanence Institute, Rochester Institute of Technology

A Guide to Fiber-Base Gelatin Silver Print Condition and deterioration

gawain

weaver

contents

Introduction

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Sidebar 1 What Color is Silver?

Sidebar 2 What Makes a Print Yellow?

The Nature of the Fiber-Base Gelatin Silver Print

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

History of Gelatin Silver Print Manufacture 6

History of Processing and Image Stability

Gelatin Silver Print Deterioration

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Examination of a Print to Judge Condition and Deterioration

Lighting
Magnification
Tonal Values

Sidebar 3 Primary Factors in Image Stability

The Basics of Deterioration

Image Decay

Gelatin Binder and Paper Decay
Mechanical Damage

Sidebar 4 Heat, Humidity, Paint Fumes, and the Benefits of Toning

Sidebar 5 Water and Fire Disasters

Deterioration Charts

Age, Deterioration, or Patina?

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Sidebar 6 The Value of Deterioration

acknowledgements:

This research would not have been possible without the Andrew W. Mellon Foundation’s generous support of the Advanced Residency Progam in Photograph Conservation held jointly at

George Eastman House and the Image Permanence Institute. My thanks also to Douglas Nishimura, James Reilly, and Grant Romer, whose advice, encouragement, and experience were invaluable in the development
and writing of this guide.

design:

Amber Hares

This paper is typeset in Adobe Caslon Pro, Catriel, and Tandelle

cover:

Lewis Hine,

Powerhouse Mechanic

, 1920 (Courtesy George Eastman House, Acc. No. 1978.0999.0018)

frontispiece:

(Page 3) Lewis Hine, [Steel worker on beam touching the tip of the Chrysler building], ca. 1931 (Courtesy George Eastman House, Acc. No. 1977.0165.0062)

info@gawainweaver.com

When is Conservation Treatment Necessary?

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Recommendations for the Storage of Gelatin Silver Prints

. . . . . . . . . . . . . . . . . . . . . .

Looking Forward

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Pathways: Deterioration in Detail

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P1: Yellow/Orange Discoloration, Edges or Overall

P2: Silver-mirroring, Edges

P3: Silver-mirroring, Overall or Localized

P4: Yellow/Brown Discoloration and Fading, Edges

P5: Yellow/Brown Discoloration, Overall

P6: Yellow/Brown Discoloration and Fading, Localized

P7: Yellowing of Non-image Areas and Highlights

P8: Image Deterioration in Localized and Uneven Patterns

P9: Gelatin Binder Lifting, Edges or Localized

P10: Staining and Tide Lines

P11: Ferrotyping and Other Surface Changes

P12: Mold Growth

P13: Planar Deformation or Cockling

P14: Embrittlement of the Paper Support

P15: Tears, Creases, Abrasion, etc: Edges

P16: Tears, Creases, Abrasion, etc: Localized

Further Reading

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

introduction

The fiber-base gelatin silver print, or black-and-white print, as it is

commonly called, was the form of virtually all twentieth-century

fine art photography. In fact, until the color revolution of the 1970s,

nearly every photograph—from snapshots to exhibition prints were

fiber-base gelatin silver prints. These prints are present in large

numbers not only in fine art collections, but in archives, historical so-

cieties, and family photograph collections. The ability to understand

and evaluate the condition and deterioration of these prints are vital

aspects of their appreciation and care.

The condition of a gelatin silver print can be described in many

different ways. Prints are often said to be warm-toned and to have

silver-mirroring or a patina. But what do we mean when we use these

words? What kind of aging process, physical change, or deterioration

are we really describing? What is their cause? What do they say about

the history of a print? And, perhaps more importantly, what do they

tell us about the future of a print? The purpose of this guide is to

answer these questions, and to make the examination of a black-and-

white print a more informative and rewarding activity. Understanding

how a print deteriorates and the visual clues that indicate the various

causes of deterioration can be very useful in the evaluation of a print’s

condition, authenticity, and material history.

This guide is designed for you if you care for gelatin silver prints as

an archivist, collector, curator, or conservator. We begin with brief

explanations about the physical nature of gelatin silver prints and a

history of their processing and stability. But at the heart of this guide

is the means to understand how and why deterioration manifests on a

gelatin silver print. The section titled The Basics of Deterioration will

be sufficient explanation for many readers, while those who desire a

more detailed understanding may want to consult the Pathways found

at the end of this guide.

introduction

SIDEBAR 1

introduction

What Color is Silver?

Silver  is  a  precious  metal  with
the  white  lustrous  appearance
that  we  see  in  silver  jewelry  or
silverware  (Figure  1).  In  pho-
tography,  however,  it  appears
quite  differently.  Instead  of  a
large  mass  of  polished  metal,
the silver that composes the im-
age in a black-and-white print is
present as very small particles,
ranging around 0.5 micrometers
in diameter. These particles are
often filamentary—composed of
long  strands  of  silver  tangled
together,  though  they  may  be-
come more rounded during pro-
cessing (Figure 2). At this size,
the  particles  of  silver  absorb
light  evenly  across  the  visible
spectrum,  generally  appearing
as  black  or  in  shades  of  gray,
depending  how  close  together
the silver particles are.

As the particles get smaller, whether by design or decay, they lose their neutral tone. Warm-
toned gelatin silver papers are manufactured with additives in the emulsion to restrain the
growth of the silver halide crystals, resulting in smaller silver grains. And as prints decay, silver
atoms can migrate away from the silver particles, gradually creating many smaller silver par-
ticles in place of the original filament. This causes a gradual warming of the image, as well as
fading, since the smaller particles appear more yellow and sometimes cannot be seen at all.

The color of silver also changes when it reacts
with  chemicals  in  its  environment  to  form  new
compounds  such  as  silver  sulfide.  This  can
occur  intentionally  during  toning,  or  over  time,
as  the  silver  image  reacts  with  chemicals  in
the  air,  such  as  hydrogen  sulfide.  When  this
process occurs over time, the silver grains tend
to disperse into smaller particles causing image
fading. In contrast, toning causes an immediate
reaction that better maintains the image particle
size.  The  particles  are  made  more  robust  by
partially converting them to silver sulfide or by
partially replacing the silver with a less reactive
metal such as gold.

Given  all  these  different  factors—particle  size,
chemical  changes,  and  toning—the  causes  of
color in a print can be very difficult to explain.
Scientific  explanations  for  the  colors  seen  in

prints are complex and cannot always account for the wide variety of colors found in them.
But subtle differences in the way a print ages can give clues to its history and the reasons
for its appearance today.

SIDEBAR 2

What Makes a Print Yellow?

Gelatin forms the matrix in
which  the  silver  image  is
suspended, and its clarity
and  transparency  are  an
important  part  of  the
viewing process. In fact, it
is doubly important, since
light  must  travel  through
the  gelatin  layer  twice
before  reaching  your
eye, multiplying the visual
effect  of  any  yellowing
(Figure 3). Gelatin is naturally slightly yellow in color, though this is not noticeable on
a gelatin silver print where the gelatin is highly refined, the coating is very thin, and
dyes are often used in the baryta to offset the color of the gelatin (Figure 4).

However, yellowing can become visible as the gelatin ages. Chromophores—portions
of a molecule that are responsible for color—can develop in gelatin as it interacts

with  its  environment. A  primary  cause  of
such yellowing is contact with poor quality
paper materials. These contain lignins and
other components that have been shown
to produce yellowing when in proximity to
a photograph.  This is one of the reasons
why  high-quality  enclosures  are  recom-
mended  for  the  storage  of  photographs,
particularly  those  that  have  passed  the
Photographic Activity Test.

Image Layer

Baryta

Paper

Left Top

Figure 1: Historic photograph of the Eastman Kodak Company’s silver vault in Rochester, NY, where silver
bullion used in making photographic film and papers is kept. In such bulk metallic form, silver has the white
lustrous appearance with which we commonly associate it. (Courtesy George Eastman House)

Left Bottom

Figure 2: Filamentary silver from a Kodak Ektalure gelatin silver print as captured by transmission electron mi-
croscopy (imaged at 16,000x). Although there are many variations in shape and structure, gelatin silver prints
typically contain this type of silver, which appears black or neutral gray. (©Government of Canada, reprinted
with permission of the Canadian Conservation Institute)

Right top

Figure 3: The viewing of a reflection print, such as a gelatin silver print, requires that the light pass
through the gelatin layer twice before reaching the eye. The same degree of yellowing will therefore
be more visible in a gelatin silver print than in a negative or transparency. (Illustration by Peter
Lazarski)

Right bottom

Figure 4: Grains of photographic gelatin in their dry state exhibit the natural yellow coloration of such
purified gelatin, even though it initially appears perfectly clear in thin photographic layers.

The Nature of the Fiber-Base Gelatin Silver Print

A gelatin silver print is composed of four layers: paper

base, baryta, gelatin binder, and a protective gelatin

layer or overcoat.

The paper base or support serves as the substrate onto

which the subsequent layers are attached. Paper is in

many ways an ideal support: it is lightweight, flexible,

and strong enough to withstand both wet processing

and regular handling. The photographic paper base

must be free of photoactive impurities such as iron and

lignins. In order to obtain this purity, the paper was

originally made from cotton rags, though after World

War I there was a transition to purified wood pulp,

which has been used ever since.

The second layer is the baryta, a white coating made

primarily from gelatin and barium sulfate. Dyes were

often added to modify color. The purpose of the baryta

layer is to cover the paper fibers and form a smooth

surface upon which to coat the gelatin.

Surfaces such as smooth, fine-grained, or silk can be

created using a variety of textured felts and marking

rollers in the making of the paper base, by variable cal-

endaring of the paper base both before and after baryta

coating, and by embossing the baryta-coated paper.

The third layer is the gelatin binder that holds the silver

grains of the photographic image. Gelatin has many

qualities that make it an ideal photographic binder.

Among these are toughness and abrasion resistance

when dry and its ability to swell in water and allow

the penetration of processing solutions. Matting agents

such as rice starch, corn starch, or silica can be added to

the gelatin binder or the overcoat to modify gloss.

The fourth layer, called the overcoat, supercoat, or

topcoat, is a very thin layer of hardened gelatin that is

applied on top of the gelatin binder. It acts as a protec-

tive layer, providing superior abrasion resistance to the

print surface.

Figure 5: Cross-section of a fiber-base gelatin silver print showing its layered structure

(Courtesy Image Permanence Institute)

overcoat

binder

baryta

paper

base

the

nature

the

fiber

base

gelatin

silver

Left

Figure 6: Eastman's Permanent Bromide Paper, ca. 1885. This very early example of gelatin silver develop-

ing out paper was available in only three types, A-Thin Smooth Surface, B-Heavy Smooth Surface, and

C-Heavy Rough Surface. (Courtesy Mark Osterman)

Above

Figure 7: This drawing and the accompanying poem appeared under the title “Photographic Failures” in

an 1846

Punch

magazine. The poem compared a photograph to love, stating how the features of a portrait

“Have vanished as affection flies—Alas !—where is it now ?”

history

gelatin

silver

print

manufacture

Now that we have an understanding of the structure of gelatin silver prints, we will

briefly explore the history of their manufacture and processing. Gelatin silver prints

were being made as early as 1874 on a commercial basis, but they were of poor quality,

being a dry plate emulsion that was coated onto paper only as an afterthought. Coat-

ing machines for the production of continuous rolls of sensitized paper were in use

by the mid-1880s, though widespread adoption of gelatin silver print materials did

not occur until the 1890s. Early papers were made exclusively on rag paper, as wood

pulp was not yet able to be purified sufficiently for photographic purposes. However,

research at the Eastman Kodak Co. following World War I led to a full conversion to

wood pulp for papermaking in 1929, and other manufacturers made the conversion

around the same time. The early gelatin silver papers also had no baryta layer. It was

not until the 1890s that baryta coating became a commercial operation, first in Ger-

many, in 1894, and then at Kodak by 1900. Although the baryta layer is important in

producing a smooth or glossy print, the baryta paper of the 1890s did not result in the

luster or gloss print surface that became the standard for fine art photography in the

twentieth century. Matting agents, light calendaring, and thin baryta layers produced

low-gloss and textured surfaces. Higher gloss papers first became popular in the

1920s and ’30s as photography

transitioned from pictorialism

into modernism, photojournal-

ism, and “straight” photography.

In the 1930s, the number of

available surfaces was at its peak.

Since that time, certain print fin-

ishes have become more popular,

others have been discontinued,

but the fundamental aspects

of gelatin silver prints have re-

mained unchanged.

history

processing

and

image

stability

Processing has played a major role over the last 100 years in the stability of black-

and-white prints, but concerns about the fading of silver-based photographs can be

traced back to the beginnings of photography. In the 1840s, William Henry Fox

Talbot’s prints became so famous for their fading that a cartoon and poem published

under the heading “Photographic Failures” appeared in the magazine

Punch

in 1846

(Figure 7). Image fading was often blamed on residual fixer (sodium thiosulfate or

hypo) in the print—sometimes due to an intentional lack of washing that was done

to achieve deep purple or brown tints. But this improved color came at the expense

of longevity, for the images soon faded to a pale yellow. In the early 1850s two-bath

fixation was already in use by Blanquart-Evrard, in an attempt to ensure maximum

permanence, in light of the poor reputation of Talbot’s prints.

The problem of fading was severe enough that the Photographic Society of London

set up a committee to address the issue in the spring of 1855. Later that year they

published their first report, citing moisture in the presence of residual fixer and/or

hydrogen sulfide as the basic reason for all fading. A majority of the committee were

of the opinion that gold toning significantly improved image stability.

Hydrogen sulfide is a product of the combustion of coal gas and was pervasive in

industrialized nineteenth-century London. Hydrogen sulfide and other pollutants

that are harmful to photographic prints can be found everywhere in varying con-

centrations. Since it was not practical to remove such contaminants, attention was

turned to the removal of fixer. Numerous methods and chemicals are recorded in the

photographic literature over the next 100 years for the elimination of fixer, culminat-

ing in the 1940s when the Kodak Research Laboratories officially recommended the

the

nature

the

fiber

base

gelatin

silver

Above

Figure 8: This portrait of George Eastman is an excellent example of the protective qualities of sulfide

toning. It has been displayed without glazing for many decades and does not exhibit even a hint of dete-

rioration. (Courtesy George Eastman House)

“complete elimination treatment” for all black-and-white photographic materials.

This consisted of Kodak’s hypo eliminator solutions, which oxidized the remaining

fixer into harmless sulfates. This extreme measure was based on the belief that even

the minutest quantity of fixer remaining in the photograph would cause image fading.

But in the 1960s, the Kodak Research Laboratories discovered something that no one

had considered before—a small amount of fixer left in a print actually forms a protec-

tive coating of silver sulfide on the surface of the silver grains. In effect, residual fixer

can act as a mildly protective toner and over-washing leaves the silver very vulnerable

to deterioration. Since there was no way to know in practice exactly how much fixer

was left in a print, the recommendation became simply to wash for the recommended

times, but not to over wash.

Toning has always been considered important for image stability. Toning can act by

replacing part of the silver image with a more noble metal such as gold or platinum,

or alternatively it can act by forming a compound with silver that is more stable than

silver alone, such as in selenium or sulfur toning. Gold and platinum toners were

often used in the nineteenth century. By the beginning of the twentieth century, when

many photographers had transitioned to gelatin silver prints, gold and platinum ton-

ers were still in use, along with newly-discovered selenium toner, and various sulfide

toners. The sulfide toners were the most protective toners ever used. However, they

generally yield a brown coloration which is disagreeable to many photographers. They

were very popular in the form of sepia toner in the 1920s and ’30s, though they were

used predominantly for portraiture. Selenium toner was perhaps the most widely

used toner in twentieth-century fine art photography, and was first disclosed in a

1910 German patent. With selenium toning the photographer could make gelatin

silver prints with a color anywhere from neutral or blue-black (i.e. no color change)

to a purple-brown, an image color that many photographers found pleasing. Thus,

photographers could benefit from the increased image stability of a toned print,

without a disagreeable change in image color. Though not as effective as sulfide toners

in protecting the image, selenium toning was a significant improvement over untoned

prints. Its use was championed by Ansel Adams as early as 1950, in the first edition

The Print

, and was a regular part of his working process throughout his career. The

excellent condition of his prints today bear witness to both his meticulous working

methods and the effectiveness of selenium toner when used properly and combined

with good print care.

Gelatin Silver Print deterioration

examination

print

judge

condition

and

deterioration

Before we discuss the types of deterioration, we must first consider the act of exami-

nation, and some of the basic vocabulary that we use in describing the parts of an

image. The importance of looking cannot be overemphasized in the understanding

of print deterioration. Proper lighting will reveal aspects of a print that cannot

otherwise be seen.

lighting

Standard

First examine the print under strong lights

and with no reflections in the surface of

the print. These conditions will allow you

to best observe the color and tonal range of

the print. These are primary indicators of

silver image condition and deterioration as

outlined in the Image Decay section below

(Figure 9).

Specular

Now position yourself so that if the print

were glossy, you would see a light reflected

in its surface. This lighting position will

emphasize surface texture and gloss, and

any changes in them due to abrasion,

ferrotyping, or mold growth, as outlined in

the Gelatin Binder and Paper Decay section

below (Figure 10).

Raking

Raking light is achieved by placing a single

light source at a very low angle to the print

surface, accentuating the surface texture and

overall topography by throwing long shadows.

Raking light will emphasize any unevenness

in the surface caused by planar deformation

or surface damage, as outlined in the Gelatin

Binder and Paper Decay and Mechanical

Damage sections below (Figure 11).

magnification

Although most significant information can be seen with the naked eye under good

lighting, you may find a moderate degree of magnification useful in some circum-

stances. A 5x or 10x loupe will generally be sufficient, though some enjoy the extra

power of a handheld 30x microscope. It takes some experience to understand what

you are seeing at higher magnifications, so be careful about drawing conclusions when

first using a magnifying device. A loupe can be useful in determining the presence or

absence of a baryta layer. Details of retouching, and whether a mark is a scratch or an

accretion, can often be revealed by magnification. However, for our purposes here, the

trained and unaided eye is usually sufficient.

gelatin

silver

deterioration

SIDEBAR 3

tonal

values

The above gelatin silver print by Frank Gohlke exhibits a full range of values from

bright white to deep black, providing a good example for the description of tonal

values in a print in good condition.

Non-image areas

are the lightest value possible in a print, where there is no silver

image, and the brightness is determined solely by the whiteness of the support and

the gelatin binder. White borders and light sources are often non-image areas.

Highlights

range from white surfaces to very light skin or light gray objects.

Midtones

range from snow in the shadows to gray stones and dark foliage.

Shadows

range from dark materials with full texture and detail to the deepest black

with no detail.

Above

Figure 12: Frank Gohlke,

Driveway, San Francisco, CA,

1979 (Courtesy George Eastman House, Acc. No.

1981.0949.0001; reproduced with the permission of Frank Gohlke)

Primary Factors in Image Stability

There are five factors that influence the long-term stability of the silver image: water,
air pollutants, heat, processing and toning, and particle size (Figure 13).

Water

in the form of atmospheric humidity swells the gelatin and allows for easier

penetration of air pollutants. Water is also a necessary participant in the degradation
of silver—it acts as the medium in which these reactions take place. Finally, migration
of silver ions through the gelatin occurs more readily as relative humidity increases,
and this migration is the foundation of silver image decay.

Air pollutants

such as hydrogen sulfide or nitrogen dioxide in the atmosphere react

with the silver image to cause fading and yellowing. Oxygen also plays an important
role, allowing deterioration to occur in the presence of moisture and heat, without the
need for more aggressive oxidizing gases.

Heat

supplies more energy for deterioration reactions. Although the effect of heat

is not as great as that of moisture, it has been shown experimentally that silver
deterioration will occur more quickly at higher temperatures.

Processing and toning

determine the composition and chemical environment of the

image particles. Fixing and washing may leave the silver image particles either only
slightly protected, vulnerable to deterioration, or highly prone to yellowing. Proper
processing followed by sulfur toning is the most effective means to prevent deteriora-
tion, while selenium and gold toning also offer some protection.

Particle size

plays an important role. Most developed-out black-and-white papers

have silver particles ranging around 0.5 micrometers (1/160 the width of a human
hair!). Slower speed papers, such as contact printing papers or printing out papers,
have even smaller particles. Since most deterioration reactions occur on the surface
of the silver particles, papers with smaller silver particles (with their greater surface
area) are often more susceptible to decay.

You may have noticed that light has not been included here as a primary factor
in image stability. Exposure to high levels of light for extended periods may cause
embrittlement of the paper support, and the associated heat may speed image silver
deterioration. However, compared to the damage that light inflicts on most color prints
or on resin-coated gelatin silver prints, fiber-base gelatin silver prints are quite stable
with respect to light exposure. Like all art on paper supports, prints on display should

be kept away from direct
sunlight or high levels of
indoor  lighting.  A  limit
of 300 lux is sometimes
used  as  a  guideline,
though  individuals  and
institutions may prefer to
set stricter standards.



Heat

Water

Particle

Size

Processing

and Toning

Air

Pollutants

Image

Stability



non

image

highlights

midtones

shadows

Figure 13: Primary Factors
in Image Stability

gelatin

silver

deterioration

Left

Figure 14: Lewis Hine,

Powerhouse Mechanic,

1920. This is a good example of a gelatin silver print in excel-

lent condition. It possesses a full tonal range with strong detail in the highlights and a nearly neutral image

color. (Courtesy George Eastman House, Acc. No. 1978.0999.0013)

Above

Figure 15: Lewis Hine,

Powerhouse Mechanic,

1920. This is a good example of a deteriorationed gelatin silver

print. The entire print has become yellowed, and the highlights have lost nearly all their detail. (Courtesy

George Eastman House, Acc. No. 1978.0999.0018)

ance, and their descriptions can be found

at the end of the guide (pages 22–39).

Sometimes deterioration can have more

than one possible cause. You can use the

deterioration charts (see pages 16–17) to

locate the Pathway that you are curious

about, or just use the references in the

text to find the right one. Each Pathway

(labelled P1–P16) is identified here in

parentheses, e.g. (P3).

image

decay

A black-and-white image would remain

unchanged for a very long time if it were

kept in a cool, moderately dry, and per-

fectly inert environment without exposure

to any airborne pollutants. Sulfide toners

can have a similar effect by converting the

silver into the very stable compound silver

sulfide. Selenium and gold toning provide

some protection, but will not protect a

print completely. In real life, there are no

such perfect environments, and few prints

are sulfur toned. For a typical gelatin sil-

ver print, image deterioration proceeds by

exposure to pollutants in the presence of

moisture and heat. The basic mechanism

of silver image decay is the same in every

case: the silver particles that form the

typical black-and-white image (Figure

14) undergo changes in their shape and

size, and may react with sulfur to form

silver sulfide. The change in particle size and the reaction with sulfur can produce

dramatic changes in the color and density of the silver image (Figure 15).

the

basics

deterioration

Now that we understand the layered structure of the print, how to best examine it,

and the primary factors in image stability, we are ready to approach the deterioration

itself. Deterioration can be divided into several broad categories: image decay, gelatin

binder and paper decay, and mechanical damage. We will examine these categories

one at a time.

There are many details to learn about each form of deterioration, so if you would like

to understand more about one of them, try reading the Pathway for that particular

type of deterioration. Each Pathway is a form of deterioration with a unique appear-

gelatin

silver

deterioration

Nearly all image decay begins with a single step: the oxidation of the image silver into

silver ions. The developed silver image is composed of particles of silver metal (see Fig-

ure 1). When silver from these particles are oxidized, they become silver ions (Ag

Unlike the silver metal (Ag

), these silver ions are able to move within the gelatin.

Thus, small dense image particles become larger clouds of even smaller particles. This

oxidation and migration of silver atoms is the first step in image decay (Figure 16).

Once the silver has been oxidized to silver ions and has travelled away from the silver

image particle it has three possible fates:

The first occurs when the migrating silver particles are quickly reduced to metallic

silver. These new and smaller particles of silver appear yellow/orange (Figure 17). This

yellow/orange discoloration typically occurs around the edges (Figure 20) and in the

midtones and may be the result of exposure to fresh oil-based paint or varnish. See

Sidebar 4 for a story of how this commonly occurs (P1).

The second result occurs in the shadows where there is a large amount of image silver.

If the mobile silver ions reach the surface of the print, they form a metallic blue sheen

known as silver-mirroring (Figure 18). This will occur only in the shadows, and either

along the edges (P2) or across larger areas of the print (P3). Silver-mirroring along

the edges is often caused by air pollutants, while more overall mirroring may be the

result of contact with poor-quality storage materials.

The third and most common result is when the mobile silver ions disperse into very

small particles of silver or react with a sulfur compound to form yellow/brown silver

sulfide (Figure 17). Depending on the size and composition of the resulting silver or

silver sulfide particles, the image may fade or shift to more yellow or brown tones.

This may occur at the edges (P4), overall (P5), or in localized areas across the print

(P6). Exposure to pollutants in the presence of moisture and heat is the most com-

mon cause. The deteriorated Lewis Hine print (Figure 15) is a classic example of

this deterioration. The silver has broken down into smaller particles and some have

likely reacted with sulfur to form silver sulfide. As a result, the highlights have faded,

and the highlights and midtones have turned yellow/brown. In this case, even the

shadows have been affected and display a warm brown tonality.

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+++++++++++

+++

Figure 16: The breakdown of a silver image particle begins with the oxidation and migration of silver ions.

Figure 17: Once silver ions have migrated

away from the silver particle, they are

reduced to either yellow/orange colloidal

silver (P1) or yellow/brown silver sulfide

(P4–P6). Although these forms of image

silver deterioration follow a similar series

of steps, they are distinct in both cause and

visual appearance.

Figure 18: Oxidation and migration of silver ions can also lead to silver-mirroring. This often occurs over

extended periods of time, as the silver ions need time to migrate to the surface of the print and form a highly

reflective layer of silver. This only occurs in the high density areas where the high concentration of image

silver allows for a large number of silver ions to reach the surface (P2, P3).

silver sulfide

colloidal silver

gelatin

silver

deterioration

A parting note on gelatin silver print image decay: while it is useful to study the indi-

vidual mechanisms of deterioration, it should be remembered that in real life, gelatin

silver prints are a complex product of their manufacture, processing, and subsequent

storage. Visible deterioration patterns will always be a complex combination of many

factors, not all of which can be fully explained.

Occasionally, faulty processing is the cause of this deterioration, and for this there

is a telltale sign—the non-image areas, where there shouldn’t be any silver at all,

will have a yellow discoloration due to residual silver/fixer compounds (P7). But be

careful in making this judgment! There is one other form of deterioration that can

look deceivingly similar. It is the yellowing of the gelatin binder that results from

contact with poor-quality storage materi-

als (P7 and Sidebar 2). Also closely related

to faulty processing are chemical stains

and other localized image deterioration

caused by contamination from chemicals

or fingerprints (P8 and Figure 19).

That was a lot of information packed into a

small space! The good news is that what you

have just read is the most difficult part of

gelatin silver print deterioration to grasp. To

better understand the causes and why some

deterioration occurs in one place and not

in another, read the Pathway description for

the deterioration that you are observing.

How do you make sense of it all when viewing a print? Try the following pointers.

print

viewing

tips

1. Use proper lighting!

2. Determine the original tone of the print by looking at the shadow areas and darker

midtones, which are most likely to have retained the original print tonality.

3. Now look at the midtones. Are they the same tonality as the shadows or have they

become more yellow/brown?

4. And finally, look at the highlights, which are the most sensitive to change. Have

they yellowed? Is full detail preserved in the highlights or have they begun to fade?

5. If there is fading or discoloration, is it occurring overall in the highlights and mid-

tones, preferentially at the edges, or in random or localized areas across the print?

6. What about the non-image areas? If there is a clear border or specular highlight

in the print, does it retain the original white or off-white color of the print, or has

it yellowed? Such non-image area yellowing can be a result of poor processing or

poor-quality storage materials. (The presence of silver-mirroring in addition to the

overall yellowing suggests that storage materials are responsible, since mirroring is

often prevented by poor processing.)

SIDEBAR 4

Heat, Humidity, Paint Fumes, and the Benefits of Toning

A well-processed and untoned gelatin silver print is a fragile object. Untoned silver
particles have a great deal of surface area and are very eager to react. Discoloration
that is simply the result of this fragility is often blamed on poor processing, but this
is not usually the case.

In  the  late  1990s,  a  New  York  City  photographer’s  work  was  exhibited  in  a  non-
climate  controlled  gallery  during  a  particularly  hot  and  humid  summer.  The  prints
were carefully processed but not toned. The photographer had never had any prob-
lems  with  her  work  before.  During  this  show,  however,  yellow/orange  discoloration
appeared along the edges in the light midtones (Figure 20 and P1). The photographer
consulted with the Image Permanence Institute in Rochester, NY, to understand the
cause and develop a solution. Selenium toning was chosen for its ability to provide
both protection to the silver image and retain the prints’ tonal aesthetic. One of the
untoned discolored prints was hung in the studio darkroom, and several years later,
when the darkroom was being repainted, the painter failed to remove the print from
the  wall  prior  to  painting  as  he  had  been  instructed. The  print  was  finally  removed

after several hours’ exposure to fresh oil-based paint fumes,
but it was too late. Within days, the yellow/orange edge dis-
coloration had extended into the midtones across the entire
photograph. What had begun by exposure to heat, humidity,
and New York City air was dramatically increased by a more
concentrated  dose  of  atmospheric  contaminants.  Identical
effects have been seen on prints by another photographer
that  were  stored  in  crates  soon  after  the  interior  of  the
crates were sealed with varnish. While toning will increase
the  resistance  of  silver  to  such  attacks,  a  combination  of
toning  and  proper  environment  is  necessary  for  complete
protection.

Left

Figure 19: Edward Weston, [Tina Modotti], ca. 1925. This small print exhibits fingerprint stains most

likely caused by the print surface being touched with darkroom chemicals such as fixer. (Courtesy George

Regents)

Figure 20: Yellow/orange edge discoloration, as seen here in this detail
from  the  right  edge  of  a  gelatin  silver  print,  is  caused  by  exposure  to
certain  air  pollutants,  particularly  peroxides.  Untoned  or  lightly  toned
prints  are  more  susceptible  than  well-toned  prints  to  this  form  of  de-
terioration.

gelatin

silver

deterioration

Left

Figure 21 (and detail): Edward Weston,

Pepper

, 1930. The frilling of the emulsion along the bottom edge is

the result of water exposure. It is emphasized in the detail by photography in raking light. (Courtesy George

Eastman House, Acc. No. 1970.0162.0004)

Above

Figure 22: Edward Weston,

Rhyolite, Nevada, Ghost Town

, 1938. The brown staining is the result of exposure

to water. In this case, it appears that the colored material was leached from nearby poor-quality boards.

(Courtesy George Eastman House, Acc. No. 1974.0061.0080)
Images by Edward Weston ©1981 Center for Creative Photography, Arizona Board of Regents

danger of the gelatin detaching from the baryta layer, particularly at the edges (Figure

21). This is known as frilling at the edges, or blistering on the surface of the print.

Frilling and blistering may occur during processing of the print as well, particularly

during extended times in processing solutions or when processing baths are at higher

than normal temperatures (P9). Exposure to water may also cause tide lines and other

water-related stains both in the gelatin and in the paper, which may be very difficult

to remove (Figure 22 and P10). A change in the surface gloss is very likely when a

print is wetted, particularly if the print dries against another surface, such as a piece

of glass. When this happens, the gelatin print conforms to the glass and assumes its

high gloss surface. This is known as ferrotyping (P11).

gelatin

binder

and

paper

decay

The gelatin binder and the paper support are both organic materials, and are sus-

ceptible to change and deterioration by exposure to water or high relative humidity

(RH). These can be the result of poor storage conditions or disasters such as flooding

or fires where water is used to extinguish the flames.

When exposed to water or high RH, the gelatin layer expands and softens. In this

swollen state, the gelatin is more vulnerable to mechanical damage. There is also a

gelatin

silver

deterioration

Even if nothing as dramatic as ferrotyping or the dissolving of the gelatin binder

occurs, fluctuations in relative humidity will readily cause cockling of a print as the

paper and gelatin expand at different rates (P13). Finally, the paper support may lose

flexibility and be at increased danger of tearing or cracking as a result of contact with

poor-quality storage materials, or excessive exposure to light and/or heat (P14).

SIDEBAR 5

If a print is damp for more than a day or two, it is also likely to grow mold (Figure

23), which can lead to staining of the paper and gelatin (P12). The mold also has a

weakening effect on the gelatin, making it readily soluble in water. If prints that are

mold-damaged are exposed to water, the gelatin layer may dissolve or lift from the

support, causing complete loss of the image. This can also occur when early gelatin

silver prints with unhardened gelatin layers are exposed to water.

Water and Fire Disasters

On Memorial Day, 1978, nitrate films stored in the Eastman House’s old incinerator
went  up  in  flames,  quickly  spreading  to  several  adjacent  buildings.  One  of  these
buildings, a previous barn, was being used for the temporary storage of a travelling
exhibition.  The  framed  exhibition  photographs  were  packed  in  crates,  and  in  the
ensuing  fire fight these crates were drenched in water. They were removed from the
building as soon as it was safe, and unpacked immediately on the museum grounds,
but not before the brown discoloration was leached from a nearby board, staining an
Edward Weston print (Figure 22).

Of course, this is the least of what could have happened. Prolonged immersion in
water, especially in the case of a print with an unhardened binder could have led to
complete loss of the image, or at least significant frilling and blistering of the gelatin
binder, and possible mold damage (Figure 23).

Left

Figure 23: Lewis Hine, [Portrait of worker, Empire State Building], ca. 1931.

This portrait of an Empire

State Building worker has sustained significant mold damage in the lower left corner, resulting in the degra-

dation and loss of gelatin binder. (Courtesy George Eastman House, Acc. No. 1977.0154.0066)

Figure 24: Fires often lead to water damage to photographic prints, such as in this fire on the grounds
of George Eastman House, May 29, 1978, (Courtesy George Eastman House)

gelatin

silver

deterioration

Figure 25 (and detail): Edward Weston,

Dillard King, Monteagle, Tennessee

, 1941. The detail highlights me-

chanical damage to the print, with complete loss of image and exposure of paper fibers in the damaged area.

Arizona Board of Regents)

mechanical

damage

Mechanical damage includes all purely physical, non-chemical damage, including

tears, creases, surface abrasions, dog ears, dents, and delamination. It is the most

straightforward form of deterioration, but it does come in different forms, and it’s

useful to be clear about the terminology we use to describe it.

The edges of a print are uniquely exposed to certain forms of mechanical damage, such

as binder folding-over and loss, delamination, and dog-eared corners. These damages

occur when the edges of a print come into contact with another object. Perhaps the

most common is folding-over of the gelatin binder along the edges. Small pieces of

binder are lifted up and folded-over onto themselves or simply broken off. This is

less noticeable when the print is overmatted or when the print has a white border.

Delamination occurs when the paper support is split at the edge, while dog-eared

corners are a combination of delamination, binder lifting, and some creasing that

occurs at the corners.

The surface of the photograph is also quite vulnerable. For example, loss of binder

by scraping may occur if a photograph is stored unprotected in a drawer that is too

full (Figure 25 and detail). Other damage, such as minor surface abrasions, tears,

and creases all fall into this category, and they can make a significant impact on the

viewing of a print.

The causes and prevention of mechanical damage are readily understandable. Careful

handling and a basic knowledge of good mounting and storage practices is all that is

needed to prevent such damage.

gelatin

silver

deterioration

deterioration

charts

These charts are designed to help you to organize the varieties of gelatin silver print deterioration in a logical manner. The charts are color coded by the type of deterioration:

yellow for

Image Decay

, blue for

Gelatin Binder and Paper Decay

, and gray for

Mechanical Damage

. When examining a print, try to match the deterioration on your print with a

description on the left side of the chart, and with a location from the right side of the chart. Often, location is the key to differentiating between similar types of deterioration.

The thumbnail images on the right are a quick reference for each

Visible deterioration

category. The text or the Pathways at the end of this guide should be consulted for more

detailed information.

Figure 26: The primary forms of silver image decay found in fiber-base gelatin silver prints. See the associated Pathway for more detailed information.

Yellowing

Non-image areas + highlights

Chemical staining

Localized + uneven

Visible deterioration

Where you see it

Pathway

(Fig. 20)

(Fig. 47)

(Fig. 15)

(Fig. 36)

Yellow/brown

discoloration & fading

Edges

Overall

Localized

Silver-mirroring

Edges

Overall or localized

(Fig. 19)

Yellow/orange

discoloration

Edges or overall

image

decay

gelatin

silver

deterioration

Figure 27: The primary forms of gelatin binder and paper decay and mechanical damage found in fiber-base gelatin silver prints. See the associated

Pathway for more detailed information.

(Fig. 50)

(Fig. 22)

(Fig. 54)

(Fig. 23)

(Fig. 57)

(Fig. 58)

(Fig. 59)

Visible deterioration

Where you see it

Pathway

Gelatin binder lifting

Edges and/or localized

gelatin

binder

and

paper

decay

Staining, tide lines

Localized and uneven

Ferrotyping

Localized

Planar deformation

Localized

Embrittlement

Overall

Mold growth

Localized and uneven

Tears, abrasion, etc.

Localized and uneven

Localized

mechanical
damage

The visible signs of age are valued, just as a vintage print is preferred over a

later print. While the aging of a print is certainly a form of decay, the line

between deterioration and patina, within fine art photography, is drawn

by aesthetics rather than science. The following comments are addressed

primarily to fine art photography, though they have relevance to anyone

interested in gelatin silver print condition and deterioration.

Some forms of aging may enhance a print in the eyes of the collector or

connoisseur. They are signs of authenticity, and, as long as they do not

disfigure the image, they are often valued. Silver-mirroring is a classic

example. A print with moderate mirroring around the edges, or even

heavy mirroring that complements the image, is enhanced by this form

of deterioration. The removal of silver-mirroring has been known to be

detrimental to a prints perceived value, as exemplified by the case of the

Edward Weston print discussed in Sidebar 6.

A warm tone is another common example of deterioration that is often val-

ued as patina. Warm-tone gelatin silver prints is an oft-used term in the fine

art market today, which can refer to both toned prints and prints warmed

by the oxidation of the image over time (P3). This photograph of Winston

Churchill is a good example (Figure 28). It is slightly warm-toned, which,

no matter how subtle or charming, is a result of deterioration. The corners

are slightly dog-eared. There is some mirroring along the edges though it

cannot be seen in the lighting used for taking this photograph. This warm-

toned effect combined with subtle silver-mirroring along the edges creates

the classic vintage print aesthetic and increases the print’s value.

Age, deterioration, or Patina?

Figure 28: Yousuf Karsh,

Winston Churchill

, 1941 (© Yousuf Karsh)

age

deterioration

patina

condition and material history of individual prints can be addressed by a qualified

photograph conservator.

What if we take the warm-tone effect a little further? This 1930 photograph by Paul

Woolf of the New York skyline has dramatically yellowed highlights and midtones

(Figure 29). However, it suits the subject. The print and its yellowing together make

a truly beautiful photographic object. The fact that it looks nothing like it did when

it was printed in the 1930s

is irrelevant. Of course, the

print is highly valued in the

fine art market.

Forms of deterioration that do

not enhance the appearance

of a print also detract from its

value. Yellow/orange discolor-

ation is always unsightly. The

color contrasts strongly with

the usual neutral, blue-black,

or brown-black appearance

of a gelatin silver print.

Severe levels of yellow/brown

discoloration and fading are

also detrimental to a print’s

value, as are chemical stains

and other uneven forms of

deterioration. Rather than

blending with or enhancing

the image, these forms of

deterioration impose a dis-

sonant pattern.

Even visually appealing signs

of age are distinguished only

by degree from the more

advanced forms that are

visually degrading. While

the signs of a vintage print can be pleasing in the present, it should be remembered

that the continuation of that same process will result in objectionable changes in the

print’s appearance in the future. A proper storage environment and careful handling

will help to ensure the stability of a print and its enjoyment by future generations.

Care should be taken in the interpretation of many forms of deterioration. Silver-

mirroring, yellow/brown discoloration, and yellowing can, under some circumstances,

be added or removed, possibly with the intention to deceive. As in any fine art field,

the provenance of a print is an important aspect of its value. Questions about the

SIDEBAR 6

The Value of Deterioration

Silver-mirroring can be a highly val-
ued aspect of a print’s condition. It
is a signifier of age and authenticity
and can be a beautiful addition to a
print’s aesthetic. The following story
revolves around the removal of mir-
roring from a valuable print. There
are many possible interpretations of
the outcome.

On April  7,  1998,  an  early  Edward
Weston  print  depicting  two  shells
was  sold  at  auction  at  Sotheby’s
New  York  (Figure  30).  A  full  page
reproduction  and  extensive  de-
scription  in  the  auction  catalog  highlighted  its  importance. A  unique  feature  of  this
print was the halo of mirroring that emanated from the edges, surrounding the shells,
and seeming to assure the print’s authenticity. It sold for $101,500 (with premium)—a
very strong price at the time.

Six years later, on April 23, 2004, the same print came up for sale at Phillips de
Pury & Company. It was estimated at $200,000–300,000, a very reasonable estimate
based on the market at that time. In the meantime, however, the silver-mirroring had
been removed from the print. In auction house terminology it was “bought in,” mean-
ing that it failed to meet the minimum price or reserve set by the seller, and therefore
went unsold. The removal of mirroring is a simple treatment from a technical point
of view. The complexity lies in the decision to remove it. Silver-mirroring is a form
of deterioration—of oxidation and migration of silver, to be specific. It is not, for the
most part, an aspect of the artist’s intentions—in fact, most photographers process
their prints carefully in an attempt to avoid such deterioration in the future. And while
mirroring can complement an image, it can also obscure it.

Did the removal of the mirroring cause a reduction in the perceived value of the print?
Perhaps. The photographic art market is very complex, and it is impossible to say
definitively why this print failed to sell the second time.

Cleaning and other conservation treatments can be done while leaving silver-mirroring
fully intact. Treatments should be considered carefully with a qualified photograph
conservator. An understanding of deterioration and its effect on value are important
factors in reaching an informed decision.

Left

Figure 29: Paul Woolf,

New York Skyline at Dusk

, 1936 (Courtesy Keith de Lellis Gallery)

Figure 30: Edward Weston,

Shells

Center for Creative Photography, Arizona Board of Regents)

Proper storage conditions are the most effective method of ensuring the long-term

preservation of gelatin silver prints. But what qualifies as proper storage conditions?

In the most general terms, proper storage means cool and moderately dry conditions,

and appropriate storage materials.

Since nearly every form of deterioration is dependent

on heat and moisture, it is important to keep your pho-

tographs out of the attic or other rooms with extremes

in temperature and relative humidity. Room tempera-

ture is acceptable, but cool or cold is preferred when it

is practical, and when humidity can be controlled under

those conditions. Freezing storage can be used, but it is

not always practical for access, and in the case of gelatin

silver prints does not provide a substantial enough ad-

vantage over cold storage to warrant

the added expense (Figures 31 and

32). (Other types of photographs,

such as color materials, or negatives

and transparencies on cellulose ac-

etate film base, strongly benefit from

the use of frozen storage). Relative

humidity should be kept moderately

low, between 30 and 50%. High RH

will accelerate chemical decay and even cause the growth of mold, while prints at low-

er RH will become brittle and more prone to cracking and other mechanical decay.

Poor-quality storage materials can also be harmful to gelatin silver prints. If possible,

prints should be stored in photographically inert enclosure materials such as 100%

cotton rag or 100% alpha cellulose fibers. If a storage material has passed the Photo-

graphic Activity Test (PAT), a very stringent testing method, you can be assured that

it will not harm the silver image or cause staining of the gelatin.

When is Conservation Treatment Necessary?

Certain forms of deterioration, caused by water, high relative humidity, or mechanical

damage are unstable and require treatment to prevent further deterioration. Binder

lifting can, under some circumstances, be unstable. Loose flaps of binder are an obvi-

ous sign of instability. Bubbles in the binder may or may not be in need of stabili-

zation. Prints with recent staining or tide lines should be referred to a photograph

conservator as soon as possible. This type of damage can often be removed imme-

diately after it occurs, but becomes progressively more difficult to treat as days and

weeks pass. Mold growth indicates a serious deficiency in the photograph’s storage

environment. Affected photographs should be air dried as soon as possible to prevent

further mold growth, and the photographs should be stored elsewhere until the envi-

ronmental problem can be remedied. Although in the case of water damage resulting

from a water or fire disaster a conservator should be involved in the recovery effort to

minimize the resulting damage. Ferrotyping can also be avoided through proper stor-

age environment. If a print is framed, be sure that it is not in contact with the glazing.

Tears and other physical damage may place the photograph at greater risk if affected

areas are fragile or otherwise vulnerable to continued damage.

Chemical decay usually cannot be reversed. Intensification and other forms of

chemical treatment are very risky and, even at their best, do not return prints to their

original state. The use of intensification on fine art prints to reverse the appearance

of silver image degradation is considered unethical in many situations. Furthermore,

experiments have shown that its use with gelatin silver prints is very dangerous and

often results in damage to the gelatin binder. Other forms of chemical treatment may

be able to reduce or eliminate yellow/orange discoloration and mirroring, though any

form of chemical treatment carries certain risks and must be evaluated carefully. There

may be some situations in which the type of print, its condition, age, and deteriora-

tion justify the risk of certain types of chemical treatment. Such decisions must be

made on a case-by-case basis.

The best treatment for chemical decay is proper storage. Prints that were poorly

processed will inevitably undergo a certain amount of yellowing, fading, or discol-

oration. There is no effective treatment that can be done to prevent this, except for

toning, which should be done during the initial photographic processing if the print

is intended to last for a long time. However, the vast majority of prints were not

improperly fixed or washed, they are simply more or less susceptible to chemical

decay as a result of the natural tendency of silver to oxidize (or tarnish) and thereby

undergo various chemical changes. Although it is often impossible to predict which

prints are most sensitive to fading and discoloration, we do know what causes this to

occur most quickly: high temperatures, high relative humidity, and air pollutants.

Recommendations for the Storage of Gelatin Silver Prints

Above left

Figure 31: Simplified storage recommendations for gelatin silver prints

Above right

Figure 32: The four temperature categories. Room, Cool, and Cold refer to “anchor-point” temperatures of

68F, 54F, and 40F, while FROZEN refers to all temperatures 32F and below.

(Courtesy Image Permanence Institute)

The twentieth century is behind us and many people now view gelatin silver prints

as an historic or alternative photographic process. We are in a period of rapid and

profound transition, in which these prints are viewed differently than they were only a

few years ago, when traditional silver-based photography was transitioning to digital

photography. As one of the most significant visual records of the twentieth century,

these artifacts are valued more and more every day. This ever-increasing value means

something different to each collector, scholar, archivist, conservator, appraiser, student,

or connoisseur, all of whom would do well to enhance their discriminative knowledge

of the twentieth-century’s gelatin silver print.

Looking Forward

Careful examination of gelatin silver prints and an understanding of how they dete-

riorate gives the print collector, connoisseur, conservator, or archivist another tool to

gain insight into the photographer’s working methods, the subsequent history and

care of a print, and its requirements in future storage, handling, and display.

Everyone has a slightly different reason for looking. Some want to know when the

print was made, others are interested in how it was made, or perhaps simply in better

understanding its current condition. The collector might wish to discriminate between

deterioration and original intent, while the conservator must understand more pre-

cisely the material or chemical nature of the deterioration in order to more safely and

effectively carry out a conservation treatment. Archivists may be responsible for large

collections, and preventing further deterioration is a fundamental aspect of their work.

For them, a greater awareness of deterioration may illuminate the consequences of

neglect, and help them set guidelines in the storage and handling of their collections.

For these and many other individuals interested in gelatin silver prints, condition and

deterioration is often one of many avenues of inquiry, and its understanding deepens

their appreciation and enjoyment of the black-and-white photographic art form.

However, an understanding of condition and deterioration is only one tool among

several that are being developed within the conservation field to gain a deeper under-

standing of the gelatin silver print. The fiber-base gelatin silver print is remarkably

complex and diverse. There is no single type of print, any more than there is a single

type of automobile. From the paper support to the baryta layer, to the gelatin binder,

every aspect of the gelatin silver print has been manufactured in different thicknesses,

with different compositions, with raw materials from different geographic locations,

applied with different machines, made with different additives, and with many and

varied textures and surfaces. The resulting variety of photographic papers that fall

under the umbrella of fiber-base gelatin silver print is staggering. This diversity allows

for many different areas of investigation.

Recent areas of study include the appearance and fading of optical brightening

agents, the identification of fibers from the paper support as a means of dating, and

even the ratio of barium and strontium within the baryta layer! An area of research

that has shown particular promise in recent years is surface. The nature of the print

surface is influenced by a variety of manufacturing choices including the preparation

of the paper, the thickness of the baryta, and the addition of various matting agents

in the gelatin binder and topcoat. The surface can be studied analytically, but it can

also be studied effectively with the unaided eye or with low-power magnification as

an important aspect of the aesthetic history of black-and-white prints and the choices

that photographers made in their own work.

PATHWAYS: Deterioration in Detail

P1:

yellow

orange

discoloration

edges

overall

Well-processed  prints  in  good  condition  are
readily  susceptible  to  this  form  of  silver  image
deterioration.  Yellow/orange  discoloration  is
caused by exposure to air pollutants that oxidize
the  silver  metal  to  silver  ions  (in  the  presence
of  moisture  and  heat),  and  then  reduce  them
back  to  metallic  silver  after  a  brief  period  of
travel  through  the  gelatin  (see  Figures  16  and
17).  Peroxides  are  particularly  effective  at
causing  this  discoloration,  because  they  have
the unique ability to act as both an oxidizing and
reducing  agent  in  relationship  to  silver.  These
silver ions travel through the gelatin and reform
as numerous smaller silver particles, known as
colloidal silver. The colloidal silver particle size

Left

Figure 33:

This detail of a gelatin silver print

exhibits yellow/orange discoloration in the

light midtones across the entire print. This is

the result of exposure to high concentrations

of peroxides from fresh oil-based paint (see
Sidebar 4).

Right

Figure 34:

This detail of yellow/orange

discoloration on a gelatin silver print shows

the typical edge deterioration pattern result-

ing from exposure to air pollutants.

that results from exposure to peroxides causes
the silver to appear yellow/orange in color.

Water  is  also  a  key  participant  in  this  dete-
rioration mechanism. Higher relative humidities
cause an increase in gelatin moisture content,
which  causes  an  increase  in  the  ability  of  pol-
lutants  to  enter  the  gelatin,  and  the  ease  with
which  silver  ions  migrate  within  the  gelatin.  In
addition,  water  is  the  medium  in  which  these
oxidation/reduction reactions occur. This is why
a moderately dry environment is so beneficial in
the preservation of gelatin silver prints.

The  dependence  of  the  deterioration  upon
exposure  to  air  pollutants  results  in  the  edges
being affected first, while more intense or long-
term exposure may cause overall discoloration
(Figures  33  and  34).  It  has  been  shown  in  the
case  of  silver-mirroring  that  enhanced  deterio-
ration along the edges is due to the relationship
between  a  flat  object  such  as  a  photographic
print  and  the  concentration  gradients  of  the
gases  in  the  surrounding  space,  which  leads
to  greater  exposure  of  the  edges  to  airborne
contaminants.  It is reasonable to assume that
any deterioration resulting from exposure to air
pollutants will follow similar edge patterns.

Whether  it  occurs  along  the  edges  or  overall,
yellow/orange discoloration is limited to the light
midtones.  Non-image  areas  do  not  have  silver
and will not be affected. Shadow areas are also
not affected.

Yellow/orange  discoloration  is  commonly
caused  by  exposure  to  peroxides  from  fresh
oil-based  paint  or  varnish,  though  it  has  also
been  observed  in  warm  and  humid  conditions
when  the  print  is  exposed  to  unknown  pollut-
ants  in  urban  air  (see  Sidebar  4).  Prints  that
are  displayed  unframed  or  without  glazing  are
more  easily  affected  by  this  form  of  deteriora-
tion since they are more directly exposed to air
pollutants.

P2:

silver

mirroring

edges

Over time some air pollutants (in the presence of moisture and heat) can create a sustained migration of silver ions in all directions.
When these silver ions reach the print surface, they form a reflective layer of silver, commonly referred to as mirroring or silver-mirroring.
It is most easily seen when the print is examined in specular light, and it appears as a highly reflective sheen with a bluish cast. Mirroring
only occurs in the shadow areas of the print where there is sufficient silver, which can be clearly seen in the print by Alfred Stieglitz,
shown here in both standard lighting (Figure 35) and specular lighting (Figure 36).

Left

Figure 35:

Alfred Stieg-

litz,

Lake George

, ca.

1930

Right

Figure 36:

Alfred Stieg-

litz,

Lake George

, ca.

1930. The silver-mir-

roring is emphasized

in this photograph by

the use of specular

lighting.

(Courtesy George

Eastman House, Acc.

No. 1974.0052.0033)

silver

mirroring

edges

When silver-mirroring forms preferentially along the edges,
it indicates that air pollutants play a role in the oxidation of
the silver. The mirroring then moves slowly inward, creating
a halo-like effect around the center of the image (Figure 37).
Be aware that mirroring, though often a good indicator that
a print is at least 20 or 30 years old, can also be removed
from a print, as described in Sidebar 6, or even added.

Mirroring along the edges caused by air pollutants can be
mimicked by a poor-quality window mat (P3). It has been
observed that mirroring often does not occur on poorly pro-
cessed prints. The sulfur from the residual fixer combines
with the silver ions to form stable silver sulfide before the
silver can travel all the way to the surface.

Silver-mirroring  is  closely  related  to  yellow/brown  discol-
oration  and  fading  (P4–6).  When  the  same  oxidation  and
migration  of  silver  that  produces  silver-mirroring  in  the
shadows occurs in the midtones and highlights, the result is
fading and or warming of the image, depending on the size,
density,  and  composition  of  the  resulting  silver  particles.
This can be clearly seen, for example, in Figure 36.

Above

Figure 37:

Edward Weston,

Shells,

1927. Shown here as re-

produced in a Sotheby’s auction catalog, this print exhibits

the classic pattern of silver-mirroring along the edges. The

story of the removal of the mirroring is told in Sidebar 6.

(Reproduced by permission of Sotheby’s, Inc.)

Below

Figure 38:

Edward Weston,

Shells

, 1927. Shown here

as reproduced in the Phil-

lips auction catalog, April

23/24 2004, the print no

longer exhibited any silver-

mirroring. (Reproduced by

permission of Phillips de
Pury & Company)

P3:

silver

mirroring

overall

localized

While  fully  purified  wood  pulp  is  harmless  to
photographs,  and  in  fact  has  been  used  for
photographic  paper  base  since  the  1920s,
paper and boards made from wood pulp (from
which the non-cellulose components have not
been fully removed) can cause staining of the
gelatin  and  image  silver  degradation.    Such
unpurified wood pulp contains lignins and other
extractives,  which  may  cause  silver-mirroring
when  left  in  proximity  to  a  gelatin  silver  print.
Paper  materials  that  often  use  this  wood  pulp
include newsprint, grayboard, and cardboard.

Image  silver  degradation  can  occur  locally  or
overall  depending  on  the  size  and  shape  of
the offending material and its contact with the
print. If the poor-quality core of a matboard is
exposed  to  the  print  only  along  the  edges,  it
can result in edge mirroring, mimicking the ef-
fect of air pollutants, as discussed in Pathway
2. If overall contact occurs with a poor-quality
paper  then  mirroring  will  appear  overall  in  the
shadows (Figure 39).

Gelatin staining caused by paper materials
made with unpurified wood pulp is discussed
in Pathway 7.

Figure 39:

A gelatin silver print from Albert Mebes’ 1913

Der Bromsilber- und Gaslichtpapier-Druck.

Overall

silver-mirroring has resulted from contact with the book’s paper that contains unpurified wood pulp.

is made to occur quickly, as in sulfide toning, the size of the silver particles
is more nearly maintained and an overall brown coloration is achieved. In
contrast to sulfide toning, when sulfiding occurs over time by exposure to air
pollutants or poor-quality storage materials, the silver has had time to oxidize
and travel through the gelatin. This leads to smaller particle size, and the
resultant fading and yellowing.

P4:

yellow

brown

discoloration

and

fading

edges

Yellow/brown  discoloration  and  fading  occurs  along  the  edges  of  a  print  for
two reasons: air pollutants or storage materials. Air pollutants will cause edge
discoloration due to concentration gradients in the air surrounding the print,
while a window mat may expose only the edge of the print to the deteriorating
effects of a poor-quality matboard. This discoloration and fading is often lim-
ited to the highlights and midtones, while the shadows remain unaffected, or
exhibit  some  silver-mirroring.  Yellow/
brown discoloration and fading can be
clearly  seen  on  the  edges  of  Edward
Weston’s  print,

St. Roche Cemetery

(Figure 40).

Yellow/brown  discoloration  and  fad-
ing  of  the  photographic  image  is  the
classic  form  of  gelatin  silver  print
deterioration.  The  mechanism  is  the
oxidation of silver to silver ions and the
migration  of  these  silver  ions  through
the  gelatin  (see  Figures  16  and  17).
The  final  disposition  of  these  silver
ions is what determines the visible re-
sult of deterioration. Some of the silver
ions  will  remains  as  silver  ions—they
are  invisible.  Other  silver  ions  nucleate  new  silver  particles  that  are  smaller
than  the  original.  Depending  on  their  size,  these  will  be  invisible  or  yellow-
ish  in  color.  Still  others  may  react  with  sulfur  to  form  silver  sulfide—a  very
stable compound. Silver sulfide can be invisible (very small particles), yellow
(medium size particles), or brown (large particles) depending on both the size
and the concentration of the particles. These varying fates of the silver ions
explain why the effect of silver image degradation is unique for the different
densities in an image. The light highlights of deteriorated prints are often faded

because the small quantities of silver form very small particles of silver or
silver sulfide. The darker highlights and midtones are yellow/brown because
of the larger amount of silver available for particle formation, and the shadows
are brown-black or even neutral. The shadows are the last to be affected, and
for various reasons often retain their original color.

It is interesting to observe the difference between the results of sulfiding
when it occurs over time through the deterioration mechanisms discussed
here and the sulfiding achieved by toning. When the formation of silver sulfide

Figure 40 (and detail)

Edward Weston,

St. Roche Cemetery,

1941. Yellow/

brown discoloration and fading commonly occur at the edges of a photo-

graph when deterioration is the result of exposure to air pollutants.

(Courtesy George Eastman House, Acc No. 1966.0070.0008; ©1981 Center
for Creative Photography, Arizona Board of Regents)

P5:

yellow

brown

discoloration

overall

Yellow/brown  discoloration  and  fading,  as  described  in
Pathway  4,  may  also  occur  over  the  entire  image  after
prolonged  exposure  to  air  pollutants  in  the  presence  of
water  (i.e.  high  RH  will  accelerate  deterioration).  It  can
also be caused by contact with poor-quality storage mate-
rials or by faulty processing. However, these two causes
may also create yellowing in the non-image areas (P7).

In  its  most  subtle  and  charming  form,  this  deterioration
appears  as  the  slightest  warming  of  the  neutral  image,
visible  only  in  the  highlights  and  midtones.  This  patina
can be a seductive attribute of an aged print, but it must
also  be  understood  for  what  it  is—a  form  of  decay  that
can ultimately lead to loss of highlight details and overall
yellow/brown  discoloration  of  the  image  silver.  As  with
edge discoloration, the shadows often retain their original
tonality or gain only subtle warmth of color. Sometimes
the  shadows  will  exhibit  silver-mirroring  (P3)  while  the
highlights and midtones fade and discolor.

Left

Figure 41:

This gelatin silver print of Winston

Churchill by Yousuf Karsh shows very slight

warming of the image. Karsh processed his

prints very carefully, and it is not likely that

this print was poorly processed. However,

this print was not kept by a museum, and

was subjected to unknown conditions,

which may have included extremes of

temperature, relative humidity, and light.

Careful processing and perhaps toning have

protected this print very well, even though

Center

Figure 42:

Paul Woolf’s gelatin silver print

of the New York skyline is more strongly

discolored than the Karsh print, but poor

processing may not be the culprit. The non-

image areas or whitest highlights are not

yellowed, so poor fixing or washing may not

be to blame. It was probably not toned, and

may have been washed for too long, leaving

the silver image vulnerable to oxidation and

migration. The image is partially converted

to silver sulfide and is thus likely to be quite

stable and not prone to further deterioration.
(Courtesy Keith de Lellis Gallery)

Right

Figure 43:

This image of Lewis Hine’s

Powerhouse Mechanic

may be our best

candidate for poor processing. The high-

lights have dramatically faded, and even the

deepest shadows exhibit a significant color

shift. Although there is no white border to

help identify yellowing of the non-image

areas, there does seem to be yellowing of

the non-image area highlights (specular

highlights) within the print, such as the

reflections in the steel above the mechanic’s

head. (Courtesy George Eastman House)

It is often assumed that this form of deterioration is a result
of poor processing. While this can be true in some cases,
it  is  an  oversimplification  that  does  not  do  justice  to  the
complexity  of  gelatin  silver  prints.  Every  factor  in  Figure
13  plays  a  role  in  the  relative  stability  of  a  gelatin  silver
image over time. Processing is one of these factors, but
even processing is not a simple question of good or bad.
Processing yields prints with varying degrees of resistance
to deterioration across a broad spectrum from nearly bul-
letproof  when  a  print  is  sulfur  toned,  to  very  susceptible
to  decay,  such  as  an  improperly  washed  or  fixed  print.
Beginning  with  this  variable  degree  of  protection,  prints
are  then  exposed  to  a  broad  spectrum  of  environmental
conditions including differences in temperature, humidity,
and  air  pollutants.  When  examining  a  print  with  overall
yellow/brown  discoloration,  keep  these  factors  in  mind,
and do not jump to the conclusion that simply because the
print is discolored and faded, it must have been processed
poorly.  Poor  processing  is  discussed  in  Pathway  6,  and
while there are some cases where poor processing is cer-
tainly the cause, in most causes it is not so cut and dry.

P6:

yellow

brown

discoloration

and

fading

localized

Localized  yellow/brown  discoloration  and
fading  is  generally  caused  by  storage  ma-
terials  or  faulty  processing.  It  is  similar  to
overall discoloration (P5), except that poor
processing  is  much  more  often  the  cause,
and  this  is  often  very  obvious.  A  common
example  is  storage  against  a  label  that  is
adhered to the back of another print, lead-
ing to discoloration in the shape of the label.
Another  example  is  the  partial  overlapping
of prints in the fixing or washing baths. This
prevents complete fixing or washing in the
overlapped  area,  leading  to  yellow/brown
discoloration in the shape of the overlapped
print.  This  yellow/brown  discoloration  is
silver  sulfide  that  forms  when  the  residual
fixer decomposes and reacts with the image
silver. The residual fixer may also react with
the residual silver from the fixing bath and
result in yellow/brown discoloration even in
areas  with  no  image  silver  such  as  white
borders or other non-image areas such as
specular highlights.

Figure 44:

Lewis Hine,

Preparing hot-house frames, truck garden, NY state

, ca. 1920. This print is

an excellent example of poor processing that leads to image discoloration. It appears that another

print was in partial contact with this print during fixing or washing, as evidenced by the right-angle

shape of the discolored area. (Courtesy George Eastman House, Acc. No. 1978.1000.0004)

P7:

yellowing

non

image

areas

and

highlights

Yellowing of non-image areas can occur for two reasons: faulty pro-
cessing and contact with poor-quality storage materials. Although
the visible result can be similar, the two forms of yellowing are very
different in nature.

Faulty processing results in silver-fixer compounds remaining in the
print  after  processing.  This  can  be  the  result  of  not  enough  time
in  the  fixing  bath,  exhausted  fixer,  or  not  enough  washing.  The
results are not immediately visible, but over time the fixer (sodium
thiosulfate)  breaks  down  and  reacts  with  the  silver  to  form  small
particles  of  yellow  silver  sulfide  across  the  entire  print. This  weak
yellow staining is generally only visible in the non-image areas and
highlights, while in the midtones and shadows it is masked by the
silver image. The residual fixer will decompose and react with the
silver image, causing yellow/brown discoloration of the image in the
highlights and midtones. If faulty processing is the cause of discol-
oration, silver-mirroring will likely not be seen, since the sulfur in the
print reacts quickly with the silver ions, preventing their passage to
the print surface (Figure 45).

These two

Equivalents

Alfred Stieglitz were made
during the same time period
and likely processed using a
similar technique. However,
one has yellowed (Figure
45), while the other remains
in

excellent

condition

(Figure  46).  The  yellowing
appears  to  be  present  in
the  highlights,  indicating
faulty  processing,  although
the  lack  of  clearly  defined
non-image  areas  makes  it
difficult to know for certain.

Above

Figure 45:

Alfred Stieglitz,

Equivalent

, 1929 (Courtesy

George Eastman House, Acc. No.

1974.0052.0023)

Right

Figure 46:

Alfred Stieglitz,

Equivalent

, 1931 (Courtesy

George Eastman House, Acc. No.

1974.0052.0013)

yellowing

non

image

areas

and

highlights

Figure 47:

The gelatin

silver prints on the

first and last pages of

this photograph album

exhibit strong yellow

staining of the gelatin

as a result of their close

proximity to the cov-

ers, which were made

with lignins-containing

board. Pictured here are

the front cover (top), a

page near the middle

of the album that was

not strongly affected

by the covers (left), and

the last page that was

in contact with the back

cover (right). (Courtesy

Katharine Whitman)

Poor-quality storage materials may also cause over-
all yellowing of the gelatin, which will be most visible
in  the  non-image  areas  and  highlights.  Although  it
can have a similar appearance, it is not caused by
yellow silver sulfide as described above. It is usually
a very subtle yellowing and is a result of interactions
between the gelatin binder and components of paper
materials  made  from  wood  pulp  from  which  lignins
have  not  been  fully  removed  (see  Sidebar  2).  The
slight  discoloration  of  the  gelatin  can  impart  to  the
print a certain aged, mellow quality that is often as-
sociated with older prints. In exceptional cases, the
gelatin staining can be quite severe (Figure 47).

Uneven processing or other chemical contamination can result in uneven
localized image deterioration. Fingerprints with yellow/brown discoloration
are sometimes seen. This can result from the handling of prints with fingers
contaminated with developer or fixer solutions. Even clean hands can result
in yellow discoloration as the salts present in sweat transfer to the photograph
(Figure 48).

Another  cause  might  be  a  mounting  or
other adhesive applied to the back of the
print. Such adhesives may be hygroscopic
and increase the localized water content
in  the  photograph,  thus  enhancing  dete-
rioration.  If  the  adhesive  were  a  rubber
cement, it could cause yellow staining as
the adhesive aged or as sulfur-containing
components of the adhesive reacted with
the image silver.

The causes of other spots and uneven patterns of de-
terioration may remain a mystery when the details of a
prints history are not known, although an understanding
of Pathways 1–7 often enable one to form a reasonable
hypothesis.

P8:

image

deterioration

localized

and

irregular

patterns

Figure 48:

Edward Weston,

[Tina Modotti], ca. 1925.

This detail shows a silver

sulfide stain caused by

touching the print surface

with fingers contaminated

with processing chemi-

cals such as fixer.

(Courtesy George East-

man House, Acc. No.

Center for Creative Pho-

tography, Arizona Board
of Regents)

Figure 49:

Lewis Hine,

From Sicily

, ca. 1905.

Silver sulfide stains

caused by what appears

to be contamination by

processing chemicals.

(Courtesy George East-

man House, Acc. No.

1977.0177.0007)

P9:

gelatin

binder

lifting

edges

localized

The gelatin (image layer) binder swells when prints
are immersed in water, whether during processing
or by accident such as during a flood or fire. Swell-
ing can lead to lifting of the gelatin binder along
the edges (also known as frilling) and lifting of the

gelatin  binder  across  the  print  as  small  bubbles  (also  known
as  blistering).  The  potential  for  damage  to  the  gelatin  binder
is dependent on factors such as the length of immersion, the
temperature  of  the  water,  the  pH  of  the  water,  the  amount  of
agitation,  and  the  sensitivity  of  the  gelatin  binder.  The  only
one of these factors which is a function of the print itself is the
sensitivity of the gelatin, which is dependent on the degree of
hardening. The sensitivity of the gelatin to water damage can
also be increased by mold (P12).

Chemical hardening of the gelatin binder occurs during manu-
facture of gelatin silver paper as well as during processing.

Figure 50:

Edward Weston,

Meraux Planta-

tion House, Louisiana

[piano close-up],

1941. Frilling of the gelatin binder can be

seen at the lower right edge of this print.

As the print does not appear to have been

damaged in a fire or flood, the frilling is

most likely a result of the original process-

ing. (Courtesy George Eastman House,

Creative Photography, Arizona Board of
Regents)

Figure 51:

Edward

Weston,

Pepper

, 1930.

This print appears to

have been damaged in

a disaster. Details show

frilling along the edges

and blistering near

the center of the print

(see also Figure 21).

(Courtesy George East-

man House, Acc. No.

Center for Creative

Photography, Arizona

Board of Regents)

Hardeners such as formaldehyde or chrome
alum  create  links  between  the  gelatin  mol-
ecules. The effect is to decrease the swelling
that  occurs  when  the  paper  is  immersed  in
water. Hardening is a balance—too much and
the gelatin does not allow sufficient penetra-
tion  of  processing  solutions—too  little,  and
the gelatin binder swells excessively, and is
more  prone  to  mechanical  damage  during
processing as well as frilling and blistering.

The  secretive  nature  of  early  manufacturing  obscures  any
detailed  knowledge  of  hardening  practices  and  when  they
began. However, conservation treatment experience indicates
that early gelatin silver papers are often very sensitive to water.
In  addition,  photographic  literature  of  the  late  nineteenth  and
early  twentieth  century  often  implies  that  early  gelatin  silver
prints, ca. 1885–1900, were not hardened during manufacture,
or were only lightly hardened.

Frilling of the binder along the edges of the print can be a part
of the original processing. This is seen particularly on prints
that receive processing beyond the standard develop/stop/
fix, such as bleaching and redevelopment, reducing, or toning
(Figure 50).

Floods and fires may also lead to frilling or blistering (Figure 51).

P10:

staining

and

tide

lines

When a gelatin silver print is immersed in
water, stains may be caused by the transfer
of colored substances from nearby materi-
als.  This  could  be  brown  organic  matter
from paper materials made from unpurified
wood pulp, or the bleeding of ink stamps or
writing from the back of the print. This most
often  occurs  as  a  result  of  water  damage
from  floods  or  the  extinguishing  of  fires
(see Figure 22 and Sidebar 5).

Prints  that  are  signed  or  otherwise  an-
notated  in  ink  are  in  danger  of  not  only
staining,  but  of  loss  of  markings  that  are
important to the provenance or value of the
print.  For  these  reasons,  a  pencil  rather
than a pen should be used for the marking
of prints or enclosures.

Figure 52:

Anonymous, [Portrait of a

young man, front and back of print],

ca. 1930. This undated portrait has tide

lines from water damage at some point

in its past. Despite the obviously poor

treatment that this photograph has

received, the image is in remarkably

good condition. This is attributable

entirely to sulfur toning, which has

converted the image to silver sulfide.

(Collection of the author)

P11:

ferrotyping

and

other

surface

changes

Even brief exposure to water
will  cause  some  change  in
the  surface  qualities  of  a
gelatin silver print. This may
be a subtle change in many
cases, while on some prints
it  will  be  quite  noticeable.
For  example,  a  ferrotyped
print, which was initially dried
against a smooth metal sur-
face to produce a high gloss,
may lose its high gloss after
wetting and air drying.

Ferrotyping  is  not  only  a
technique  used  to  produce
a  high  gloss  on  fiber-base
prints. It also refers to a form
of  print  damage,  when  a
print  is  exposed  to  water  or
a high relative humidity while
in  contact  with  a  smooth
surface.  The  gelatin  swells
and  reforms  in  the  shape
of  the  surface  it  is  contact-
ing.  A  common  example  is
when  framed  photographs
are  pressed  against  their
protective  glass  and  either  accidentally  exposed  to  water
or exposed even briefly to a warm and humid environment.
These types of surface changes are most easily observed in
specular  light,  as  can  be  seen  in  the  images  of  an  Edward
Weston  print  in  normal  (Figure  53)  and  specular  lighting
(Figure 54).

Left

Figure 53:

Edward Weston,

Belle Grove Plantation House, Louisiana

[open window], 1941.

Right

Figure 54:

Edward Weston,

Belle Grove Plantation House, Louisiana

[open window], 1941. The ferrotyping damage is emphasized when
specular illumination is used.

(Images Courtesy George Eastman House, Acc. No. 1966.0070.0040;
©1981 Center for Creative Photography, Arizona Board of Regents)

P12:

mold

growth

The properties of gelatin as it interacts with water
make it an ideal photographic binder, but as we have
seen, it also makes it susceptible to damage by water.
As a hygroscopic protein, gelatin is also an excellent
medium for biological growth.

If prints remain damp or in conditions of 70% RH or
higher for more than a day or two, there is a high risk of
the onset of mold. These microbes secrete enzymes
that  breakdown  the  gelatin,  allowing  it  to  dissolve
easily in water. Damp basements, water leaks in the
storage  area,  floods,  and  the  extinguishing  of  fires
with  water  are  all  conditions  that  often  lead  to  mold
growth.  If  there  are  limited  environmental  controls,
even high humidity weather conditions can be enough
to place your photographic materials in danger.

Left

Figure 55:

Lewis Hine, [Portrait

of worker, Empire State

Building], ca. 1931. Water-

damaged photographs often

exhibit severe mold damage

and consequent staining and
loss of emulsion.

Right

Figure 56:

Lewis Hine, [Portrait

of worker, Empire State

Building], ca. 1931.

Specular

lighting highlights the loss

of sheen resulting from the

breakdown of the gelatin
binder.

(Images Courtesy George

Eastman House, Acc. No.
1977.0154.0066)

The growth of mold weakens the gelatin, but it will also
likely create stains that will be very difficult to remove,
since  treatment  in  water  becomes  difficult  once  the
gelatin  has  been  weakened. The  colors  of  mold  vary,
and black and red stains are commonly found on mold
damaged photographs (Figure 55). Mold damage to the
gelatin  binder  will  always  result  in  a  loss  of  gloss  in
the  print  surface,  most  noticeable  in  specular  lighting
(Figure 56).

Mold  may  also  grow  on  the  paper  support  or  mount,
though  it  will  not  weaken  the  paper  as  rapidly  as  the
gelatin  binder.  Staining  and  tide  lines  are  often  seen
on  the  paper,  though  these  may  not  be  visible  when
viewing the print from the front.

P13:

planar

deformation

cockling

The two primary layers of a gelatin silver print, the paper and the gelatin binder,
expand and contract at different rates in response to changes in relative humidity
and temperature. To understand this better, first consider a sheet of uncoated
photographic paper and a sheet of gelatin separately. The sheet of gelatin is uni-
form in its composition and will expand and contract uniformly along its width and
length. In contrast, the sheet of uncoated photographic paper has a grain direc-
tion, meaning that the paper fibers are oriented preferentially in a single direction,
called the machine direction. This is the direction of travel of the paper as it was
being formed on a papermaking machine. An interesting property of paper fibers is
that when they are wetted, their width increases more than their length. So a sheet
of paper will expand more across its width (against the grain, or cross machine
direction) than it will along its length (with the grain, or machine direction).

Now let us return to a gelatin silver print. When it is wetted, the paper and the
gelatin both expand and become limp. As it dries the gelatin contracts equally in
both directions. The paper and gelatin shrink about the same amount along the
width of the paper (against the grain), but in the grain direction, the paper does not
shrink nearly as much. The result is that as the gelatin dries and shrinks it pulls the
paper up, causing a curling of the paper. Keep in mind that the grain direction is
not necessarily related to the orientation or the size of the image or the paper.

The above description is the very simplest case and is the cause of print curl.
However, what if the paper dried along the edges faster than at the center, or the
gelatin dried before the paper, or the mounting prevented the print from expanding
along the top edge? Any of these and many more situations like them, which influ-
ence the expansion or contraction of the paper or the gelatin, will cause planar
deformation or cockling either locally or overall.

Figure 57:

Leon Levinstein,

Residential Area, Morgantown, West Virginia, June

1935

, 1935.

Planar deformation of this print is accentuated by photography

in raking light, and includes cockling along the top edge of the print and a

slight curling of the vertical edges, indicating a horizontal machine direc-

Greenberg Gallery, NYC)

P14:

embrittlement

the

paper

support

The flexibility of a photographic print is an important quality in its long-term physical stability. This flex-
ibility enables it to withstand the rigors of handling with a minimum of damage. Flexibility can be lost
over time as the paper is exposed to moisture, heat, and the degrading effects of poor-quality storage
materials. These can lead to a shortening of the cellulose chains and a consequent embrittlement of the
paper support. This loss of flexibility, combined with improper handling, may lead in turn to cracking of the
photograph. Generally speaking, photograph supports are of very high quality, and it requires a very poor
environment to cause this level of decay. However, older photographs, particularly those made before the
1930s, have more variability in their quality, and may be more prone to brittleness.

Figure 58:

Lewis Hine, [Slums,

shantys, and people], ca. 1910.

Embrittlement of the paper has

led to significant losses along

the edges of the print. (Courtesy

George Eastman House, Acc. No.

1978.1025.0026)

P15:

tears

creases

abrasion

etc

edges

Damage to a print as a result of handling and poorly designed storage
is one of the most common forms of deterioration. Such damage gener-
ally occurs very quickly and proper handling and storage will prevent
any further damage.

The edges and corners are particularly vulnerable to mechanical dam-
age as they are most often in contact with hands, mounting corners,
and other objects. The most common forms of damage include bending
of the corners, delamination of the paper support, and separation of
the gelatin binder from the baryta layer. Left untreated, this can lead to
areas of complete loss of the image layer along the edges.

Figure 59:

Edward Weston,

Meraux Plan-

tation House, Louisiana

[piano close-

up], 1941. Delamination of the paper

support and folding-over of the image

layer and upper layer of the paper sup-

port are clearly evident in this detail of

the top edge. (Courtesy George East-

man House, Acc. No. 1973.0248.0002;

Arizona Board of Regents)

P16:

tears

creases

abrasion

etc

localized

While edges are often the first and most common place
to  find  mechanical  damage,  the  surface  of  the  print
can  also  be  affected.  Damage  to  the  surface  often
has an influence on the viewing of the print. Scuffing,
light scratches, and minor surface abrasions are quite
common on older prints, and can be quite distracting
depending  on  their  severity.  The  image  itself  is  not
usually affected, since the topcoat protects the image
layer. In addition, the silver is distributed throughout the
image layer, such that small losses at the surface do
not remove an appreciable quantity of silver image.

More severe forms of mechanical damage include
creasing or tearing of the photograph, deep scratches,
and complete loss of areas of the print—most often
the corners.

Left

Figure 60:

Lewis Hine,

Italian family looking for lost

luggage

, 1905

Right

Figure 61:

Lewis Hine,

Italian family looking for lost

luggage

, 1905.

This detail, taken with specular illu-

mination, highlights surface cracking that resulted

from flexing of the print. Cracks in the image layer

are not common, as it requires significant stress to

induce them. This may occur when the gelatin im-

age layer of a print has become brittle and is then

flexed. Such lack of flexibility may be the result of

age-embrittlement or very dry conditions, such as

below 20% relative humidity.

(Courtesy George Eastman House, Acc. No.

1977.0177.0134)

Eastman Kodak Company (1979).

Preservation of photographs

. Rochester, NY:

Eastman Kodak Co.

Eaton, G. T. (1965).

Photographic chemistry in black-and-white and color photography

Hastings-on-Hudson, NY: Morgan & Morgan.

Eaton, G. T. (1987). History of processing and image stability. In

Pioneers of

photography: their achievements in science and technology

. E. Ostroff (Ed.). Springfield,

VA, The Society for Imaging Science and Technology: 87–93.

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Funderburk, K. (2006).

History of the papermills at Kodak Park

. Rochester, NY:

self-published.

Gmuender, C. (1992). On black-and-white paper image-stability enhancement ef-

fectiveness of toning treatments on silver gelatin prints determined by the hydrogen

peroxide fuming test (M.F.A. Thesis, Rochester Institute of Technology, 1992).

Gray, G. G. (1987). From papyrus to RC paper: history of paper supports. In

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. E. Ostroff (Ed.).

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Haist, G. M. (1979).

Modern photographic processing

. New York: Wiley.

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The stability and preservation of recorded images

. New York:

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graph conservation: a study guide

. Toronto, Ont., Canada: Lugus.

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Photographic Science and

Engineering 9

(2), 121–132.

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Conservation management and archival survival of photographic

collections

. Göteborg, Sweden, Acta Universitatis Gothoburgensis, Göteborg

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further

reading

Adams, A. (1950).

The print: contact printing and enlarging

. New York: Morgan &

Morgan.

Bernier, B. (2005). Issues in the humidification and drying of gelatin silver prints.

Topics in Photographic Preservation 11

, 6–16.

Brandt, E. S. (1984). Mechanistic studies of silver image stability. 1: Redox

chemistry of oxygen and hydrogen peroxide at clean and adsorbate-covered silver

electrodes.

Photographic Science and Engineering 28

(1), 1–12.

Brandt, E. S. (1984). Mechanistic studies of silver image stability. 2: Iodide adsorp-

tion on silver in the presence of thiosulfate and the influence of adsorbed iodide on

the catalytic properties of silver toward hydrogen peroxide.

Photographic Science and

Engineering 28

(1), 13–19.

Brandt, E. S. (1987). Mechanistic studies of silver image stability. 3: Oxidation of

silver from the vantage point of corrosion theory.

Journal of Imaging Science 31

(5),

199–207.

Burge, D. M., J.M. Reilly, and D.W. Nishimura (2002). Effects of enclosure papers

and paperboards containing lignins on photographic image stability.

Journal of the

American Institute for Conservation 41

(3), 279–290.

Crabtree, J. I., G.T. Eaton, and L.E. Muehler (1940). The elimination of hypo from

photographic images.

The Photographic Journal

, 458–469.

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salts from photographic materials as affected by the composition of the processing

solutions.

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stability of black-and-white silver materials.

Journal of Imaging Technology 12

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57–65.

Eastman Kodak Company (1930).

Commercial photo finishing

. Rochester, NY:

Eastman Kodak Co.

Eastman Kodak Company (1952).

Stains on negatives and prints

. Rochester, NY:

Eastman Kodak Co.

further

reading

Reilly, J. M., D.W. Nishimura, K.M. Cupriks, and P.Z. Adelstein (1991).

Sulfiding

for protection for silver images. Final report to the office of preservation National Endow-

ment for the Humanities

. Rochester, NY: Image Permanence Institute, Rochester

Institute of Technology.

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Petherbridge (Ed.),

Conservation of library and archive materials and the graphic arts

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Ware, M. (1994).

Mechanisms of image deterioration in early photographs: the sensitivity

to light of W.H.F. Talbot’s halide-fixed images, 1834–1844

. London: Science Museum;

Bradford National Museum of Photography, Film & Television.

Wentzel, F. and L.W. Sipley (1960).

Memoirs of a photochemist

. Philadelphia:

American Museum of Photography.

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