Preservation of Mixed Photographic Collections
With an ever-increasing interest in visual history as an adjunct to written and oral history, pressure is being placed on a wide variety of photographic collections. The following is offered as an introduction to preserving photographic items that may be found within family archives, genealogical and historical societies and other collections.
Photographic collections can include a wide variety of photographic processes and as these require differing treatment due to the nature of the process used, it is essential to correctly identify the types of photographs in a collection. The format of a photograph will affect how it is stored and treated; the one photographic process may include large items in original frames through to small loose photographs devoid of any original casings or mounts. With correct storage and handling, photographs can be protected from any further damage arising from exposure to heat, light, moisture, insects and mishandling.
Identification of Photographic Processes
Photography has recently celebrated one hundred and fifty years since the patenting of the first photographic process in 1839. In Australia, the first recorded photograph was taken in May 1841. Fortunately, the daguerreotype being the earliest type of photograph, has proved to be the most durable, enabling us to appreciate early photographic views and portraits of great clarity and detail.
The daguerreotype, invented by Louis Daguerre, consists of a polished silver plated copper sheet, which should be accompanied by a mat and protective cover glass, and placed within a velvet-lined leather-covered case. The composition of cases may vary, in particular the American union case. Some images were hand-coloured with finely ground pigments. Salted paper prints or calotypes are rare in Australia; they did not gain the popularity that daguerreotypes enjoyed, probably due to lack of definition inherent to the calotype process. The surface has a matt finish and the yellow or brown image is usually quite faded.
The ambrotype was a popular process in Australia from the early 1850's to the early 1870's and was a faster cheaper alternative to the daguerreotype. A more fragile artifact than the daguerreotype (in terms of handling), the ambrotype process involves coating a glass plate with collodion mixed with potassium iodide and made light sensitive in a bath of silver nitrate. The plate then had white highlights and the shadows were clear glass, which when backed with black velvet, paper or lacquer appeared as a positive. It is easier to view than a daguerreotype which has a mirror-like surface and can be viewed only at certain angles. The ambrotype is usually housed in a decorative case similar to the daguerreotype, or may be framed.
The tintype or ferrotype is another style of ambrotype where the collodion is coated onto a sheet of blackened iron to produce a direct positive image. They were often pasted onto a paper card with a window opening, and were a cheaper and more portable alternative to the glass ambrotype.
The albumen print is the most common type of print in 19th century photography. From 1855–1895, both portraits and landscapes were produced using the albumen process. Albumen or egg white containing sodium chloride was coated onto smooth surfaced, high quality thin paper stock. Sensitised with silver nitrate, the image was printed in direct contact with a negative using daylight. It was gold toned to give a purplish-black colour, then fixed in sodium thiosulphate. Albumen prints may be indentified by the thin paper stock and also by a crazed or crackle pattern in the emulsion. While this pattern is sometimes visible to the naked eye under raking light, it can be more easily idenitified under magnification. Prints are usually faded, losing the deep purplish tone and appearing yellow brown in some instances. The highlight details fade and turn a characteristic yellow tone. Most prints were mounted on cardboard of varying standard panel sizes, and sold as carte-de-visite and cabinet portraits. Larger prints were mounted into albums or were framed.
Glass plate negatives date from around 1858, and may be collodion or wet-plate, or the later gelatine dry-plate dating from around 1880 in Australia. The wet-plate negative was coated by the photographer on location, and used in the camera whilst still wet to obtain maximum light sensitivity. The plate is characterised by thick, unevenly cut glass, flow marks from the emulsion which was poured on by hand, and is yellowed. Wet plate sizes ranged from quarter
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to whole plate and sometimes larger. The gelatine dry plate negative was mass produced and usually sold in boxes of ten. They are therefore of uniform stardard sizes, ranging from ninth plate to whole plate size.
1Collodion printing out papers were marketed in the 1880's initially with a glossy surface and later a matt surface — depending on prevailing tastes. They were gold toned which has given them a reasonable degree of permanence. However, as collodion does not absorb water or swell in contact with moisture, this led to processing difficulties. The gelatin paper prints introduced later in the same decade came to outsell the collodion papers by the early 1890's, and the gelatin process has continued to the present day in the form of gelatin silver black and white prints.
Platinotypes, available in England from 1880, were processed in Australia in the 1890's and possibly earlier. The process results in an image consisting of pure platinum, as the potassium oxalate developer dissolves ferrous salts and caused the platinum to reduce to a metallic state. This gives a very stable image, characterised by a long scale of tonality from soft greys to solid blacks, usually on a matt surface. Brown tones could be achieved by adding mercury to the sensitive coating or by altering developing procedures.
Opalotypes in Australia date from 1882, and were mostly made from 1890–1900. The image can be albumen, gelatin or carbon process on a white milk glass; some were hand coloured. Variations in size occur, although most measure 20 × 25 cm and 25 × 30 cm. Larger sizes and oval shapes exist.
The twentieth century has seen the proliferation of colour processes. Discussion of the various colour processes is not intended here, and storage of colour items is discussed later.
Storage Requirements
Deterioration of photographic artifacts can occur due to a multitude of factors, acting either independently or in conjunction with each other. Some photographic processes are less stable than others, and depending on how the photograph was processed originally in terms of eliminating as many residual chemicals as possible, all affect stability of a photograph.
Cased photographs such as the daguerreotype and the ambrotype may have suffered from another human factor: curiosity! These cased items are sometimes dismantled by well-meaning owners or custodians who thereby cause irreversible damage if carried out in an uninformed manner. There are various components of a photographic item that deteriorate under certain conditions. Cased items have a glass component which is chemically unstable due to the soda in the glass being susceptible to high levels of relative humidity. The glass weeps, forming droplets on the inside of the glass, which can obscure the image or attack its surface. Daguerreotypes rely on having an airtight seal, and once this has been broken then severe oxidation can set in, as well as contamination by airborne sulphur gases and other air pollutants, resulting in loss of image. Brass mats and pinchbeck preservers are also prone to corrosion at high levels of relative humidity. Storage in individual folding acid-free boxes is recommended for cased items, which are then usually stored flat. If the cases are in good condition, then they may be stored vertically once they are boxed.
The ferrotype's iron support will corrode at high relative humidity. Ferrotypes that are cased can be housed in the same manner as other cased items. Those that are loose or pasted onto card could be sleeved in good quality plastic sleeves (such as Mylar D). Acid-free paper could also be used but necessitates double handling when retrieving images.
Albumen prints usually deteriorate due to several factors acting in concert. Research has been, and still is, being conducted at Rochester Institute of Technology, New York, and has found that carbonate buffered storage papers in direct contact with albumen prints can lead to yellowing of the print.
23 There are alternatives to using alkaline buffered papers, and an acid-free unbuffered paper or board of neutral pH is recommended. Such papers or boards include Phototex tissue and Photographic Storage Paper, both made by Archivart; Atlantis Silversafe paper; Rising Museum photomount board and Mylar D. Other unbuffered acid-free tissues and glassine paper are available through other archival suppliers.
Gelatin prints, because of their protein content could also be stored in unbuffered enclosures and the products suitable for albumen prints can apply to gelatin prints. Otherwise, they should be stored in materials buffered to pH 7.2 — 9.5.
4 Depending on your requirements, loose prints may be placed in albums, or housed in protective boxes. Albums should be of acid-free archival quality and the photographs mounted using mounting corners or acid-free paper hinges. Mounting corners can be made from Mylar D or acid-free paper. Spray adhesives, PVA and other adhesives that are non-reversible must not be used for mounting photographs. Non-archival albums can damage photographs and so a careful selection of album must
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be made. Boxes for housing loose prints must fit the prints, and preferably have folding flaps so the prints are easily accessed without causing damage. The prints should be interleaved with acid-free tissue or paper.
Glass plate negatives are often found stored in their original boxes and this usually means there are no separate enclosures for each negative. The emulsion on each plate is therefore at risk from abrasion and scratching. When such boxes of glass plates are stored horizontally, the weight of the plates may cause cracking or breakage of plates at the bottom of the box. Glass plates should be individually sleeved or enclosed in adhesive free folders of acid-free paper. Once the plates have been enclosed correctly, then they should be stored vertically, on edge in sturdy archival boxes.
Cellulose negatives require further identification before they are housed and stored. Cellulose nitrate negatives were manufactured 1889–1951, cellulose acetate from 1923– present, and polyester base from 1960 to the present. Cellulose nitrate based film goes through five stages of deterioration, but only at the fifth stage has it chemically decomposed to a highly flammable condition.
5Cellulose nitrate negatives should be kept separate from other photographic artifacts, as gases emitted from decomposing nitrate film can affect other photographic emulsions. It is recommended that nitrate negatives be duplicated onto safety film, and that the National Film and Sound Archive be contacted before considering disposing of any nitrate film. Storage at low temperatures can inhibit chemical deterioration to a certain extent.
Slides have been produced on both colour and black and white film, usually in 35mm format, but sometimes in 120mm format. There are various commercially available forms of folders. When considering the storage most appropriate to your needs, consider that wood, PVC and paints all give off gases that affect film dyes. Different slide films and chemical processing will react differently in terms of dye stability.
6 Metal cabinets with baked enamel finish provide a dark, well-ventilated environment suitable to slide storage. If slide pages are to be used, choose ones made from polypropylene or polyethylene. Folders with PVC covering should be avoided.
Negatives, both colour and black and white, must be kept in archival quality enclosures, protected from light. As most negatives slide into an enclosure, it is essential to maintain cleanliness of negatives to avoid abrasion. Use of a soft blower brush to remove surface dust or grit is recommended before sleeving negatives.
Colour material benefits from storage at low temperatures; use refrigeration where long term storage is required. Kodak manufacture storage envelopes made from polyethylene, aluminium and paper for these purposes, and modern frost-free refrigerators/freezers can be used.
7Contemporary colour prints have inherent problems with instability of the colour dye layers. Display of colour prints in uncontrolled situations will lead to a breakdown of the dye structure, and prints can be observed to turn green or magenta overall. A popular way to house prints is in an album; however, this is recommended only if the album is made from safe archival materials. If an acid-free album cannot be used, then use an album in which photographs are mounted using photocorners. The pages can then be interleaved with acid-free paper so that the emulsions of the photographs do not come into contact with each other. This would be preferable to the ‘magnetic’ style albums which have a layer of plastic which holds down the photographs onto an adhesive treated page. The adhesive can cause staining of the prints and if moisture becomes trapped between the plastic layer and the photograph, the image of the photograph can be broken up by fungus or by the plastic layer itself when it is lifted.
Display of photographs
Display of photographs can include both prints and transparencies. Transparencies are displayed either through projection using bright light for short periods of time, or larger formats can be back-illuminated for long periods of time using lower light levels. Where possible, avoid display of original material, and instead use copy prints or duplicate transparencies. Ultraviolet light must be avoided, including natural daylight and ultraviolet emitting fluorescent tubes. Light levels from 50 lux to 160 lux are recommended. Levels over 160 lux can cause fading.
8 Approximate measurement of light levels can be taken with a manually operated camera.
9 Photographs should not be stored or displayed in areas of high or fluctuating humidity or in extremes of temperature, such as near heating appliances or external walls, as these factors can result in emulsion cracking. Framed work can be ‘spaced’ from the wall by small plastic ‘framer’ buttons or little pieces of cork attached to the back of the frame. This allows better air circulation and discourages insect nesting.
Where paper prints are mounted onto acid-free board, either hinges of acid-free paper adhered with starch paste or archival mounting corners may be
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used. If framing is intended, a mat or window mount must be used so that the surface of the photograph does not come into contact with the glass or perspex in the frame. UV Perspex is recommended for prints being displayed, in particular, albumen prints. Lengthy display of albumen prints is not recommended, and no works should be displayed in light sources containing ultraviolet light.
Photographs should be handled carefully to avoid deposit of perspiration and oils from fingertips on the surface of prints and film. Clean white cotton gloves should be worn when handling photographs. If it is necessary to annotate a photograph, use 2B or 3B pencil on the verso of the print; ink pens are not recommended.
The phrase “store in a cool, dry place” is a good starting point for photographic storage. Add to that: clean, dark, controlled atmospheric conditions (30–50% relative humidity and constant low temperature) and a healthy environment for photographs would be achieved.
Having identified and organised correct storage and handling of a photograhic collection, it may still require further treatment to stablilise or restore damage already incurred by some of the photograhic items. At this stage, professional conservators or photographic restorers should be consulted. Photographic emulsions can be in a very delicate and susceptible state, especially when they have suffered some deterioration. An experienced professional is required to treat such items, or may be prepared to give advice on how to stablilise the condition of items that require treatment.
References
Brian Coe and Mark Harworth-Booth, A guide to early photographic processes (London, Victorian and Albert Museum in association with Hurtwood Press, 1983).
T. J. Callings, Archival care of still photographs (Sheffield, Society of Archivists Information Leaflet No 2).
Conservation of Photographs (Rochester, Eastman Kodak Company publication F-40, 1985).
Alan Davies and Peter Stanbury, The Mechanical Eye in Australia (Melbourne, Oxford University Press, 1985).
Laurence E. Keefe and Dennis Inch, The life of a photograph (London, Focal Press, 1984).
James M. Reilly, Care and identification of 19th century photographic prints (Rochester, Eastman Kodak Company publication G-2S, 1986).
Siegried Rempel, The care of black and white photographic collections: identification of processes (Ottawa, Canadian Conservation Institute, Technical Bulletin No 6, 1980).
Mary Lynn Ritzenhaler et al, Archives and Manuscripts: Administration of photographic collections (Chicago, Society of American Archivists, 1984).
Robert A. Weinstein and Larry Booth, Collection, Use and Care of Historical Photographs (Nashville, American Association for State and Local History, 1977).
Mary Cox
For reproductions of many of the processes described in this article, the interested reader is referred to the recent publication In Focus, Australia's Heritage in Stamps, by Mimi Colligan (Australia Post Philatelic Group, Melbourne, 1991).
