The Preservation Handbook Online

Table of Contents

Introduction
I. Preservation
II. Assessment
III. Collection Assessment
IV. Agents of Deterioration
V. Monitoring collections
VI. Materials
VII. Storage
VIII. Conservation
IX. Security
X. Disaster Planning
XI. Housekeeping
XII. Resources / Suppliers
XIII. Preservation Grants

Materials - Photographs

 

Photographs - introduction

Photographs are laminated structures composed of final image material, binder layer, and primary support.

Final image material is the substance which absorbs and scatters light to produce the photographic image. Types include: metallic silver, platinum metal, pigments, and dyes.

Binder is a transparent layer in which the final image material is suspended and protected. Binders play an important role in optical properties and stability. Types include: albumen - white of eggs; collodian - a form of cellulose nitrate used in the 19th century; gelatin - a highly purified, commercially prepared protein, produced from animal hides and bones.

The primary support can be paper, metal, plastic, or glass and acts strictly as a structural support. The composite nature of photographs will challenge preservation efforts.

Photographs come in numerous types and sizes with unique preservation needs. The most common formats are, negatives and positive prints either black and white, tinted, toned, or colored.

Common deterioration:

Photo oxidation; ultraviolet exposure; bio-deterioration; physical and mechanical; improper storage.

Photograph - identification, stability and storage

Five key areas to dating and identification of photographic process:

- positive or negative
- nature of support material - metal, glass, ceramic, stone, paper, leather
- texture, surface quality
- color, tone
- characteristics of deterioration

Storage

-Shelves composed of wood, metal and plastic products are potential threats to works of art on paper. Padding and acid barrier should be in place. Drawers should be lined and can be further sub-divided with acid-free mat board or cardboard.

-padding: polyethylene foam, cotton, synthetic felt, polyethylene batting.

-liners: Mylar (polyester), Marvelseal (metal foil), heavy acid-free, buffered paper, unbleached muslin; aluminum, polyester, polyethylene sheeting, blotters, rag mat or acid-free, buffered corrugated cardboard.

-encapsulation: Mylar (except with fryable media)

-relative Humidity: 30 -50% (ideally 30 -40%)

-temperature: Not to exceed 18° C. / 65° F.

-air filtrations for particulates; air purification to remove oxidizing gases.

Safe products for contact

All paper products in contact with photographs should pass a Photo Activity Test (P.A.T.) to ensure products are free of chemicals that might damage the image.

Rag board; acid-free paper cardboard; glassine; inert plastic such as polyester film or acrylic sheeting; Japanese paper (100% Kozo); purified starch paste.

All works should be matted for storage to prevent materials from contacting the face of the photograph. Unmatted photographs can alternatively be stored in acid-free paper folders or envelopes.

Slip sheets: neutral glassine (transparent) or buffered tissue (opaque).

Boxes: acid free boxes either prefabricated or custom built.

Framed works should be stored vertically with acid-free cardboard interleavings. Covering with opaque fabrics and paper aid in slowing light damage.


Types of Photographs

Negatives: wet plate; dry plate; flexible base/paper, glass, acetate, polyester

Prints: salted, albumen, platinum, collodian, silver gelatin

Nitrate-based film - (1890 - 1951) Inherently unstable; film base for emulsions popular in the 1920s and 1930s. Composed of cellulose nitrate, a highly flammable compound. Requires special storage conditions including buffered acid-free paper enclosure and cold storage. Cellulose nitrate is motion picture film.
No plastic enclosures.

Acetate Negative - (1920 - present) Known as safety film, typically suffers from permanent shrinkage due to loss of solvents and plasticizers. (Vinegar Syndrome) producing channeling. Hard to burn, safety marked on the edge. Store in buffered acid-free paper based enclosure. Environmental fluctuations are very damaging stabilizing relative humidity is most important factor.
No plastic enclosures.

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One layer - uncoated paper

Paper negatives (mid 1830 - mid 1860)
One layer structure where image-forming silver is directly on paper. Usually waxed or oiled. Originals should be stored in chemically inert plastic sleeves made of either cellulose triacetate or polyester (Mylar - D), unbuffered paper envelope and handled as little as possible. Light sensitive and should be duplicated. Rare

Salted paper prints, calotypes (1830 - mid 1860)
Light sensitive paper placed in contact with a negative and set in sun until image prints out, printing-out process. Warm toned images; tending towards a brown, purple, or reddish color; matte surface; paper fibers visible; often faded to pale yellow, especially at the edges; sometimes varnished; could be heavily retouched. Originals should be placed into plastic sleeves made of either cellulose triacetate or polyester (Mylar - D), unbuffered paper envelope and handled as little as possible. Light sensitive and should be duplicated

 

Cyanotype (mid 1830 - mid 1860)
Distinctive blue tones; no gloss; image material embedded in paper fibers; and no surface coating. Store in chemically inert plastic sleeve and un-buffered acid-free paper envelope. Short display time with low lighting.

Plantinotype (mid 1830 - mid 1860)
Can see paper fibers; very crisp appearance; very little sheen. Originals should be stored in chemically inert plastic sleeves made of either cellulose triacetate or polyester (Mylar - D), unbuffered paper envelope and handled as little as possible. Non-silver process, images do not discolor or fade.

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Two layers - paper and emulsion

Albumen (1855 -1885)
Formats Carte-de-viste (2.5 x 4.5 in.) Cabinet Card (4.5 x 6.5 in.)
Smooth, thin, high quality paper floated on an a binder made of egg whites and sodium chloride, eventually will yellow the image. The albuminized paper is placed in silver-nitrate solution to make it light sensitive Treated paper is placed in direct contact with a negative and exposed to sunlight or "printed-out." Image is toned with gold chloride, fixed in sodium hyposulphite to remove light reactive salts and thoroughly washed. Purplish brown or black images. Most albumen prints are mounted on acidic materials such as cardboard accelerating deterioration. Very susceptible to oxidation leading to image fading, discoloration and loss of highlights. Under magnification surface appears cracked from uneven expansion. Heavy white stains are caused by degradation of the albumen protein.

Store in chemically inert plastic sleeves and unbuffered acid-free paper envelope. Short display times with low lighting.

Carbon (1850 - present)
"Print fading was a common occurrence in the earliest days of photography, and several people sought to address themselves to this problem. In the mid 1850s some began to experiment with carbon, and in 1864 Joseph Wilson Swan perfected the process, which he also patented.
Prints made using this process came in any color, and were permanent. The sensitizing solution consisted of a mixture of carbon, gelatin, the coloring material, and potassium bichromate. Once the paper was exposed to light, the areas exposed became insoluble in water. Development consisted of washing the unexposed soluble material away in warm water.
The image being laterally reversed, it needed to be transferred to another base which was usually paper, but which could be leather or wood; the image was in relief.

A variation on the carbon process was the Woodburytype, introduced a year later."xxxii

Used to reproduce works of art, and as tip-ins for books. Subtle image relief; paper fibers visible in highlights; no fading or yellowing; may get large cracks in dark areas; can be any color

Store in chemically inert plastic sleeves and unbuffered acid-free paper envelope.

Woodburytype (mid 1850 - 1910)
"This is a form of photographic printing, mentioned here because it appears almost identical to a photograph. The process was patented by Walter Woodbury in 1866, and is similar to the carbon process. The great feature of the Woodbury process is that a photograph in gelatine is caused by enormous pressure to indent a sheet of lead. The quality of the pictures was remarkable, with no grain, and the process was widely used until the turn of the century." Leggat, R. (1999)

Store in chemically inert plastic sleeves and unbuffered, acid-free paper envelope.

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Three Layer - paper, baryta, emulsion, coated with plastic

Collodian chloride - printing out paper (1890 - 1920)
Glossy and matte textures; used primarily for studio portraiture. Glossy pictures are warm gold, toned in color. Matte pictures are olive-black, toned in gold and platinum. Coated with light sensitive salts dispersed in collodion. Placed in direct contact with negative; exposed to light; toned with gold or platinum salts; and fixed. Stable image that rarely fades. Binder becomes brittle and prints appear abraded. Usually mounted; paper fibers not visible.

Silver gelatin - developing out process (1880 - 1960)
Exposed to enlarger light as opposed to sunlight. Chemically developed in a reducing agent, fixed, and washed. Produces warm tones; matte, glossy, and high texture prints. Will yellow and fade with exposure to ultraviolet radiation. Exhibit using highly reflective iridescence in dark areas.

Negatives or prints should be stored in chemically inert plastic sleeves
(uncoated-polyester) and unbuffered, acid-free paper envelope.

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Encased photos

Daguerrotypes - Direct positive process (1840 - 1860)

Union case made of leather or guda rubber poured into mold. Can experience red rot resulting from chemically unstable tanning processes used in the 19th century. Guda rubber will eventually harden in the presence of oxygen. Damaged cases can be rehinged.

The image surface is mirror like and reflective, often hand colored with pigments.

- silver platted sheet of copper
- image highlights are a combination of silver, mercury, and gold.
- shadows are pure silver metal.
- copper or brass mat
- copper liner
- brass powder scalloping

The presence of tarnish and corrosion indicate exposure to moisture and air borne pollutants. The result will be fading and eventual loss of image on the silver coated plate. Daguerrotypes often suffer from deteriorating cover glass with low lead content. Daguerrotype cases should not be opened. Corrosion should not be removed. When treatment is necessary a conservator should be contacted. Two types of electrochemical cleaning are available: tinfoil - electrolyte solution; battery solution.

Daguerreotypes and other cased images should be stored in handmade phase boxes measured to fit, or modified document boxes sealed tightly to protect from moisture and aggressive chemicals.

Ambrotype (1851 - 1880)
Hand coated collodian glass. Glass plate immersed in a solution of silver-nitrate; exposed to light in a camera; immediately developed, washed, fixed, and varnished. Highlights: white, highly reflective silver particles. Black paper, black painted glass and occasionally ruby glass creates the shadows. Ambrotypes use a reversed image, giving a ghostly appearance. Can be tinted but isn't normally.

Deterioration characteristics: flaking of collodian binder or black paint; discoloring or yellowing of varnish; broken glass support. Usually very little evidence of tarnish or fading from oxidation.

Ambrotypes in Union case should be stored in handmade phase boxes measured to fit, or modified document boxes sealed tightly to protect from moisture and aggressive chemicals.
Ambrotypes without cases should be kept in filing enclosure or four-flap envelope made of high alpha-cellulose, or chemically inert plastic such as uncoated polyethylene, cellulose triacetate, and polyester

*The paper must be sulpher and peroxide free to avoid chemical reactions. No Glassine

Tintypes, Ferrotypes, Melainotype (1856 - 1900s)
Collodian coating onto black lacquered iron, happening. Exposure to moisture will cause rusting of the support. Characteristic milky gray highlights. Can use a magnet to identify presence of iron plate.
Tintypes in Union case should be stored in handmade phase boxes measured to fit, or modified document boxes sealed tightly to protect from moisture and aggressive chemicals.
Tintypes without cases should be kept in filing enclosure or four-flap envelope made of high alpha-cellulose, or chemically inert plastic such as uncoated polyethylene, cellulose triacetate, and polyester.

Glass plate negatives

Collodian wet plate (1851 -1880)
Plated coated by hand; edges are ground; uneven coating at the edges; varnished.

Gelatin dry plate (1880 -1975)
Plate is machine coated; cut edges; even coating at edges; occasionally varnished. xxxi

Common sizes are 4 x 5, 5 x 8, and 8 x 10. Suffer most from structural damage. The first enclosure for broken or complete glass plate negatives is a four-flap envelope made from acid-free, lignin- free heavyweight paper. . They should be sleeved and stored vertically in a grooved box or packed tightly in an acid-free object box. Broken glass plate negatives require a more involved process to prevent further deterioration. Robert Herskovitz, the chief conservator for the Minnesota Historical Society, released an excellent technical leaflet on glass plate negative storage in the "Interpreter" in 1999.

Water may damage emulsion on glass plate negatives; airborne pollutants can bleach exposed emulsion; acid in synthetic materials will initiate chemical reactions; ink from enclosures can "print through" onto photographic emulsion; and adhesives from envelopes can bleach emulsion.

This article is currently available online at: <http://www.mnhs.org/about/publications/techtalk/TechTalkJuly1999.pdf>

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Color

Color film and negatives are unstable in light and dark storage. Color images are made from organic dyes instead of metallic silver leaving them susceptible to fading.
Chromogenic processes employ color couplers to produce dyes in the emulsion layers during processing. In dark storage unreacted color couplers may induce staining - giving an overall yellow discoloration. Chromegenic materials include: papers used for printing negatives; some papers for positive color transparencies; and all color negative films. Deterioration is due to chemical instability; improper developing techniques; and high temperature, or relative humidity.

Color photos that need to be displayed should be migrated to Fuji-Inax Ceramic Color Photograph format/ "Fuji-Inax Photocera Ceramic color photographs, which are available only in Japan, use inorganic pigments to form images on ceramic plates which are fired at high temperatures. The resulting "photographic ceramic tiles" are claimed by fuji to be unaffected by light, rain, seawater, and fire."xxxiv

Color slides should be migrated to color separation negatives.

Photo albums should be boxed and interleaved with acid-free tissue if necessary. Do not stress the binding.

 

Web-based Resources by: Paul Messier - Photo conservator

 

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Citation

XXXII Leggat, R. (1999) The carbon process. A history of photography. Online, url:http://www.rleggat.com/photohistory/history/carbon.htm Accessed o1/o3/o3
XXXIII Types of photographs (2001). Technical Leaflet. Andover MA.: Northeast Document Conservation Center
XXXIV Wilhelm, H. and Brower, C. (2001). The permanence and care of color photographs: traditional and digital color prints , color negatives, slides, and motion pictures.