Picturescope. Vol. 30, Num. 1. Spring 1982. pp. 34-37
James M. Reilly is lecturer at the School of Photographic Arts and Sciences, Rochester Institute of Technology.
In September 1979 a research project was undertaken at Rochester Institute of Technology to investigate the causes and mechanisms of deterioration in albumen photographic prints. This research has been conducted by myself and three very able assistants: Douglas G. Severson (now at the Art Institute of Chicago), Constance A. McCabe, and Nora Kennedy. The research was made possible by grants from the National Museum Act (administered by the Smithsonian Institution), the National Historical Publications and Records Commission, and the National Endowment for the Humanities. The project is scheduled to end in September 1982.
The following summary of findings is based on formal publications which will appear in 1982 and which will give detailed accounts of the research methods and results. The formal results will appear in the Preprints of the 1982 annual meeting of the American Institute for Conservation and in the Preprints of the 9th International Congress of the International Institute for Conservation. The purpose of this summary is to make the major findings available in a nontechnical digest form, so that they may be of use to curators, archivists, librarians, and others directly concerned with the preservation of albumen prints.
About 80 percent of the photographic prints surviving from the nineteenth century are albumen prints. Because relatively few negatives have survived from that time, the legacy of nineteenth-century photography in its original form is largely constituted of albumen prints. Unfortunately albumen prints are among the least stable of all silver photographic materials. In spite of the fact that all albumen prints received a gold-toning treatment during processing (gold treatment is a very effective way of increasing the stability of silver images), the image is easily affected by moisture and a variety of other agents. At the present time 90 to 95 percent of extant albumen prints are significantly deteriorated. Considerable experience and familiarity with the original appearance of albumen prints are required in order to appreciate the extent of deterioration that has already occurred. So many prints have faded, changed color, yellowed, and lost highlight detail that it is difficult to realize how much beauty and information has been lost from them; in their original condition albumen prints were usually a rich purple-brown, with white highlights and full detail in all parts of the tonal scale.
We began the research by postulating that albumen prints had deteriorated for the same reasons that modern black and white prints do, namely poor fixing and washing when the prints were first made. The plan for the research was to make new albumen prints that resembled nineteenth-century prints as closely as possible, then subject them to elevated temperature and humidity as a way of artificially aging them. Most of our studies were carried out at 50° Centigrade (122°F); coupled with high humidity this relatively moderate temperature induced severe deterioration within a very short time. To test the effects of bad processing, albumen prints were prepared with various amounts of washing and then incubated at 50° C and four different moisture levels—30, 50, 75, and 95 percent RH. Another series of experiments tested the effects of fixer exhaustion. Changes in the samples were measured by comparing reflection density readings made before and after incubation.
After two repetitions of the washing series and three of the fixer exhaustion series it was quite dear that albumen prints are effectively washed in a very short time and that the use of exhausted fixing solutions is associated with easily recognizable symptoms not found in the majority of deteriorated albumen prints. A survey of processing regimes given in nineteenth-century photographic manuals revealed that most of them offered very conservative recommendations on fixer exhaustion rates and if anything, recommended too much rather than too little washing. The experiments showed conclusively that bad processing was not the cause of the widespread deterioration of albumen prints.
Figure 1. Relationship between ambient Relative Humidity and image fading (density loss) in albumen prints
The most surprising outcome of the experiments with processing variables was the amount of fading and yellowing produced in well-processed samples by incubation in air and moisture. These results showed that albumen prints are inherently unstable under conditions of high relative humidity. The relationship between fading and ambient RH can be seen in figure 1, where density loss in a high density area is plotted against ambient RH. This graph presents the most pertinent and useful information for the preservation of albumen prints that the research project has uncovered. Of particular importance is the dramatic in-crease in the amount of fading when the relative humidity exceeds 60 percent. The data in the graph are from sixty days of incubation at 50°C.
All albumen prints are extraordinarily sensitive to moisture, much more so than black and white materials, and control of relative humidity is the most important aspect of preserving them. The recommended RH for storage of albumen prints is 30 to 40 percent. Albumen prints are not equipped to withstand "ordinary" conditions in temperate climates, where summer heat and humidity are quite high; in areas without high summer humidity, such as Denver, the condition of albumen prints in collections is far better on the whole than in East Coast cities. The few albumen prints that have survived in excellent condition have done so because they were somehow shielded from air and moisture.
The rate of deterioration of albumen prints at a given set of conditions decreases over time, so that the maximum rate of fading is always observed in the initial stages of the process. Therefore prints that have remained in excellent condition are much more sensitive to their environment than those that have already deteriorated. Excessively high relative humidity is not required in order for serious deterioration to occur. Unless temperature and relative humidity are strictly controlled, it is unreasonable to assume that the albumen prints now in good condition will remain so for very long. The importance of humidity con-trot in the preservation of albumen and similar gold-toned printing-out papers cannot be overstated.
A typical pattern of image deterioration in albumen prints subjected to air and moisture includes a yellowing of the white parts of the print, complete loss of the lighter tones such as detail in light clothing and faces, the change of image color from purple to yellow-brown, and also an overall lightening (fading) of the deepest tones. The yellowing of highlight areas in albumen prints is partly a result of the egg white itself turning yellow. In a reaction known as the Maillard reaction, sugars present in albumen react with the egg proteins to form yellowish-brown products. Another cause of highlight yellowing is the formation of small particles of silver in white areas of the print. Silver that once was part of the image becomes quite mobile during deterioration, and some of the silver ends up as small particles in formerly white areas, giving them a yellow coloration.
Apart from highlight yellowing, most of the image instability of albumen prints is a consequence of the physical form of the silver and gold image. The individual particles that make up the image in albumen prints are almost unimaginably tiny, so small that they lie at the lower limit of the resolution of the electron microscope. The reason why albumen prints (and other printing-out papers) lose their lighter tones so much faster than black and white prints is because in all printing-out papers the lighter tones are comprised of fewer and smaller particles than in deep shadow areas. Small size makes the particles in albumen prints much more reactive, especially in the highlights. In black and white prints made by development the particles are always much larger than those of albumen prints, and they are the same size in both highlight and shadow areas, so highlight detail is not lost so rapidly.
One of the most surprising findings of the research was the fact that alkaline conditions accelerated the yellowing of albumen prints. This has important consequences for the choice of filing enclosures and matting materials for use with albumen prints. Incubation experiments showed that when alkaline-buffered papers such as PermalifeTM were kept in direct contact with albumen prints at high humidity, more highlight yellowing was produced than with filter paper or an inert plastic like MylarTM. While acidic conditions minimized highlight yellowing, more image fading was produced, so filing enclosures for albumen prints should not tend to alter the pH either to the acid or alkaline side.
For these reasons alkaline-buffered paper enclosures and mat boards should not be used in direct contact with albumen prints. Several other points should also be noted: (1) high humidity is required in order for the alkalinity of the enclosure to migrate to the print, (2) direct contact between the enclosure material and the print is necessary for the print to be adversely affected, and (3) the amount of additional yellowing produced in these experiments by alkaline conditions is not so severe as to mandate hasty changes in storage enclosures. Rather, this evidence suggests that an alternative to alkaline mat boards and enclosures is needed for albumen prints. These alternative materials—perhaps high alpha-cellulose, nonbuffered papers—should be thoroughly tested in incubation studies with albumen prints, then gradually integrated into collections to replace existing enclosures and house new acquisitions.
The research needs to be done to identify safe enclosure materials, not only for albumen prints, but also other printing-out papers. Recently several cases of severe damage to albumen prints by contact with mat boards have been reported, apparently due to the release of oxidants from within the mat boards. This resulted in severe staining of sky areas and simultaneous bleaching of shadow areas in contact with the overmat. The image structure of albumen prints makes them especially vulnerable to oxidative attack, and in these cases the prints were affected in a very short time. We would like to hear from Picturescope readers who may have had a similar problem with damage to albumen prints from contemporary mat boards. Oxidants may come from many sources and pose a threat to albumen prints in storage. Fumes from certain oil-base paints, automobile exhaust, ozone from electrical equipment (including some office copiers), and fumes from various plastics have all been identified as sources of oxidants dangerous to photographs in storage.
Proper care of albumen prints must be based on the awareness that they are extraordinarily sensitive to moisture. There is a striking contrast between albumen prints and modern black and white materials in that the latter are often poisoned by inadequate processing, yet are reasonably stable if well processed in the first place. On the other hand, albumen prints are usually adequately processed but are inherently far less stable. One important lesson from this investigation into albumen print deterioration is that photographic materials have very different characteristic behaviors. Major historical materials must be investigated individually if their preservation needs are to be properly understood.
For storage of albumen prints the following conditions are recommended: relative humidity: 30 to 40 percent; temperature: less than 18° C. A provisional recommendation for paper enclosures for albumen prints is the use of neutral, high alpha-cellulose paper without carbonate buffering. Uncoated polyester and cellulose triacetate also appear safe.