Conservation of photographic materials.
- Angela H. Moor,
- Ian L. Moor
- and Susie Clark
The conservation of photographic materials relates to the passive and interventive techniques used to clean, stabilize, consolidate, repair, and restore original photographic positive and negative images.
See also Photography
1. Assessment and preventative conservation.
- Angela H. Moor and Ian L. Moor
Conservation for photographic materials must take into account the characteristics and properties that denote the photograph as an artifact, rather than just a visual image, and historic and technological information must be preserved to ensure the continuation of the provenance of the photograph. Regarding the photograph as an image will include all the visual, social, historic, artistic, and aesthetic information that is represented within the picture created by the photographer. This concept also relates to the individuality of style, interpretation, and presentation of the photographer in respect of that which he purposefully or accidentally captured in his work. Regarding the photograph as an artifact will include the visual and material characteristics that make up and form the essence of the photograph. These physical properties include the light-sensitive coatings found in non-colloidal images such as calotypes, salted paper prints, cyanotypes, and platinum prints or in the image-carrying colloid or colloidal emulsions, whether silver or pigmented, and their supporting bases, mountants, and presentation materials. These properties are relatively easy to recognize (see Photography, §I). Less easy to identify are the visual and material characteristics that are products of the individual photographic process and photographic technology, the photographer’s skill, and the manipulations and adaptations that are personal to him. Condition is also an inseparable part of the intrinsic make-up of a photograph, as all photographic images exist in an altered, imperfect state. The one factor affecting image condition is image permanence. Of all human artifacts the photograph is possibly one of the most sensitive and vulnerable to physical and chemical degradation, on all levels of its existence.
Photographs are prone to degradation by both external and internal factors. External factors affecting image permanence in photographic materials are, firstly, environmental, including light, temperature, humidity, and air quality. Other factors include poor storage environments and support materials, careless handling, and benign neglect. Internal factors affecting degradation are mainly residual processing chemistries, migratory contaminants, and physical incompatibilities. In addition, the inherent qualities of the component materials being affected must be considered. First, the base or support material: this can be either paper, glass, metal, leather, wood, fabric, ceramic, bone, or a transparent synthetic support. These materials will react independently to the image-bearing emulsion, inducing physical incompatibilities. Emulsions also vary. Second, the colloid emulsion: if present this can be albumen, collodion, gelatin, or gum arabic and all of these materials are degradable as a direct result of their inherent qualities. For example, albumen has a natural free sulfur element in its composition; collodion, a nitrated cellulose, is susceptible to both chemical and physical degradation; gelatin and gum arabic are susceptible to high humidity, mold attack, and acid and alkaline conditions. These materials will react independently to their support. Third, the photographic image: for all intents and purposes the photograph is classified as a work of art, but unlike its counterpart the painting or drawing it cannot effectively be restored using the same media, photographic chemistries, related processes, and techniques that produced it. Lastly, the inherent chemical characteristics: the deliberate degradation of known sensitive materials such as silver nitrate, iron III compounds, and bichromated colloids, by light and chemical oxidizing agents, gives rise to the phenomenon known as a photograph, and yet these very same agents must be controlled in order to prevent the photograph from being degraded to the point of destruction. Contemporary color photographs present an additional problem in the inherent instability of the dye chemistries in chromogenic materials, positives, and negatives.
All photographs clearly exist in a vulnerable state. It is of vital importance to understand fully the nature of the materials used in the original process, for it not only allows an appreciation of the physical subtleties inherent in individual photographic processes, enhancing still further the reputation of the photographer, but it also enables ethically sound preservation, conservation, and restoration techniques to be formulated. Examining more closely the phenomena of color in the monochrome processes, for example, will help us to understand and recognize these often intangible physical characteristics, while clearly showing the interrelationship between all of the component aspects. Image color in photographs is dependent upon several factors, including the relative size, formation, density, and concentration of the visible image-forming silver particles and their respective spectral reflectance values; the singular or combined use of light-sensitive salts; the actinic quality of light during exposure; and the influence of temperature and humidity upon the image production processes. In addition, the surface texture of the image support, coated or uncoated, alters its spectral reflectance value depending upon the amount of light refraction. Other factors concern the addition of pigments to bichromated colloids and the presence of additives to paper bases or other porous supports in the form of loadings and sizes that interact with the various halides or combinations of halides during the initial reaction. Also important is the influence of pH upon the image production processes. The majority of photographic processes are based upon the effects of acids or alkalis upon organic or inorganic compounds where changes in material state are brought about by the reaction between acid and alkaline substances. In all cases the resulting photograph is either acid or alkaline stabilized. Lastly, attention must be paid to after-treatments, tones, and intensifiers used in the original production of the image. In addition to the physical characteristics of a process and its materials, it is equally important to preserve all original modes of presentation and containment, including decorative or accredited mounts, album forms, and printed photographic ephemera.
Since all photographs have a natural life span, there will be an inevitable change in their visual and material characteristics. To place degraded material in good storage conditions will not in itself ensure its long-term preservation. It is necessary, therefore, as part of any preservation and conservation policy, first to stabilize the photograph and its mode of presentation by the removal of particulate and, where possible, material contaminants. The purpose of preservation and conservation is to slow down, and hopefully to arrest, the processes of degradation, many of which are very subtle, thereby preserving the integrity of the artifact.
- Hunt, R. Researches on Light. London, 1844.
- Hardwich, T. F. A Manual of Photographic Chemistry. London, 1855. Rev. 7, ed. G. Dawson, as A Manual of Photography. London, 1873.
- Eder, J. M. Geschichte der Photographie. Vienna, 1905, rev. Halle, 4/1932; Eng. trans., New York, 1945 R/1978.
- Jones, B. E. The Cyclopaedia of Photography. London, 1912, R/1982.
- Clerc, L. P. Photography Theory and Practice. London, 1971, rev. 2/1972.
- Reilly, J. M. The Albumen and Salted Paper Book: The History and Practice of Photographic Printing. Rochester, NY, 1980.
- Reilly, J. M. Care and Identification of 19th-century Photographic Prints. Rochester, NY, 1986.
- Martin, E. Collecting and Preserving Old Photographs. London, 1988.
- The Imperfect Image: Photographs, their Past, Present, and Future: Papers Presented at the Centre for Photographic Conservation’s First International Conference: Windermere, 6–10 April 1992. London: Centre for Photographic Conservation, 1992.
- Hendricks, K. B., and others. Fundamentals of Photograph Conservation: A Study Guide. Toronto, 1992.
- Wilhelm, H. and Brower, C. The Permanence and Care of Color Photographs: Traditional and Digital Color Prints, Color Negatives, Slides and Motion Pictures. Grinnell, IA, 1993.
- Stratis, H. and Salvesen, B., eds. The Broad Spectrum: Studies in the Materials, Techniques, and Conservation of Color on Paper. London, 2002.
- Eismann, K. Photoshop Restoration & Retouching. Berkeley, CA, 3/2006.
2. Remedial treatments for photographs.
- Susie Clark
Remedial treatment refers to the practical treatment of individual photographs, which have been damaged or have deteriorated, with the purpose of improving their condition and enabling them to be used and enjoyed. Different materials have been used and different approaches have been taken to remedial treatment since the official announcement of the invention of photography in 1839. Since the 1980s and the advent of professional conservation courses and raised standards in institutions holding photographic collections, the term has been used both to describe professional conservation treatments and to distinguish them from restoration.
All traditional photographs consist of an image which is held on a support or carrier. Sometimes there may also be additional layers and materials serving a variety of functions. The conservation problems of photographs can be broadly divided into three groups: physical, chemical, and biological. Types of physical damage are tears, creases, and holes. Chemical damage includes problems such as fading, color change, and tarnishing. Biological damage usually results from insects, mold, or rodents. All these types of damage can be aggravated or caused by a poor storage or display environment and poor handling.
In the 19th century, most alterations made to photographic images were cosmetic (retouching of processing blemishes or enhancing the appearance of the subject matter). These were sometimes carried out at the time by the photographer or later by other people. Repairs were carried out on prints in an ad hoc fashion, often using patches or splints of paper and whatever adhesive might be available. Likewise photographs on glass were repaired with a variety of adhesives.
Some of these repairs and alterations would now be considered akin to restoration and not conservation. Restoration, by contrast with remedial conservation treatment, is more invasive. It aims to return a photograph to its original appearance. However, restoration may be cosmetic and superficial only and it does not necessarily help the original components of the photograph to last for longer. Indeed sometimes it will actually increase the rate of deterioration of the original components. It is also more subjective than conservation and involves a considerable degree of guesswork, particularly for example where there are large missing areas. In the 19th and 20th centuries restoration also grew to include chemical treatments of silver processes. These were usually designed to remove tarnish or strengthen the visibility of the image. These techniques were mostly carried out on daguerreotypes and silver developed-out images, both negative and positive. Problems may arise in these cases as treatments were usually applied to the whole photograph and were frequently difficult to control. Effects may appear such as dark patches in previously light areas. As a result of the sometimes unpredictable results of restoration techniques and the subjectivity of their use, they are generally considered to be unethical in the field of modern photographic conservation.
Since the 1980s, the general care of photographs (preservation) and remedial conservation have constituted the overall field of photograph conservation. Both will usually be the responsibility of a professional photographic conservator.
The field of conservation draws on the experiences of photographers who invented and developed photographic processes as well as those who attempted to treat them in the past. Modern practitioners of remedial treatment for photographs require knowledge of art, history, and science, as well as good manual dexterity and visual judgment. They need to be aware of developments in new techniques and materials. Remedial conservation treatment is carried out by professionally trained individuals with an academic qualification or equivalent experience and sometimes accreditation. Different qualifications are found in different countries. Many modern conservators started their professional training in paper conservation and have studied further to increase their knowledge of the other materials which may be found in photographs. The purpose of remedial treatments since the 1980s has been to enable as much as possible of the original material to survive in good condition for as long as possible, allowing the photograph to be used in its original context as much as possible. This would include the immediate surroundings of the photograph, for example albums, cases, and mounts. It is important to care for the original photograph as duplicate or digitized copies will never contain as much information as the original photograph or have the same significance. In many cases, an original photograph has the capacity to outlast a copy produced using later techniques.
The remedial conservation of photographs is not done out of context. Treatment of a photograph or collection of photographs will include a practical assessment of the probable use of the photograph, for example how frequently it might be displayed and how it might be transported. Physical damage would usually be treated with repair techniques, such as the use of splints of conservation material with conservation adhesive to mend tears. Chemical damage is often difficult to treat and problems such as fading cannot usually be reversed. In this instance the best that can be achieved is often to improve the environment, including surrounding materials so that further deterioration is avoided. Dirt and stains can sometimes be removed dry by cleaning materials that lift off the surface deposits. If that is unsuccessful, the use of solvents may be considered by the application of poultices, gels, or varying degrees of washing. This will depend on the sensitivity of the photograph and associated materials. The careful application of humidity can be used for certain processes to reduce creases, folds, and distortions. Biological damage takes many forms such as holes and discoloration. Sometimes physical repairs are necessary and at other times, chemical treatments may be used.
Frames, cases, and boxes may be an integral part of the photographic object, but it may be necessary to add conservation materials to the package surrounding the photograph to isolate it from potentially damaging components. These conservation materials are usually out of sight but play an important part in prolonging the life of the photograph. The conservator will consider many external factors when deciding on an appropriate treatment. Housing for individual photographs or collections will often be improved at the stage of remedial conservation to ensure that once the photograph is conserved it is better protected from physical and chemical damage. Damage has often resulted in the first place from poor quality housing. Examples of materials which can cause damage are papers and boards made from wood pulp and plastics such as PVC (polyvinyl chloride). Unfortunately, the era of photography has coincided with poorer quality papers and boards used for boxes, cases, album pages, and in frames. Photographs are often very sensitive to a poor storage environment. Fortunately, in recent years there has been more awareness of the need for better quality storage materials. Individual clients and institutions are often given recommendations for the photograph’s future care alongside remedial conservation.
- Hendriks, K. B., and others. Fundamentals of Photograph Conservation: A Study Guide. Toronto: Lugus Publications, 1991.
- Ware, M. Mechanisms of Image Deterioration in Early Photographs. London: Science Museum and National Museum of Photography, Film and Television, 1994.
- McCabe, C., ed. Coatings on Photographs Materials, Techniques, and Conservation. Washington, DC: Photographic Materials Group of the American Institute for Conservation of Historic and Artistic Works, 2005.
- Lavédrine, B. Photographs of the Past Process and Preservation. Los Angeles: Getty Conservation Institute, 2009.
- Hess Norris, D. and Gutierrez, J. J., eds. Issues in the Conservation of Photographs, Readings in Conservation. Los Angeles: Getty Conservation Institute, 2010.
- Pénichon, S. Twentieth Century Color Photographs Identification and Care. Los Angeles: Getty Conservation Institute, 2013.