The conservation of photographs is a comparatively new field of study, fostered by the increasing awareness that photographs are valuable, and often unique, records of people, places, events, and important documents and graphic information. The proper evaluation, treatment, and preservation of the many different types of photographs held in thousands of public and private collections require specialized knowledge and skills. The growing demand for such specialists has been met partly by graduates of the various conservation programs and partly by others trained as interns in large archives, museums, and libraries throughout the world.

The National Archives of Canada has played a particularly active role in this area under the leadership of Klaus B. Hendricks, director of the Conservation Research Division. The principal purpose of this study guide is to help conservation students acquire a thorough understanding of the most important photographic materials and processes used to produce still photographs, as well as gain the expertise required for the identification, treatment, and preservation of individual photographs and photographic collections. Another aim of this formidable, copiously illustrated, and exceptionally well-documented manual is to help establish professional standards for the training of conservators in this relatively new but rapidly growing field. To this end, the problems encountered by a conservator responsible for a large photographic collection such as that of the National Archives of Canada are examined in detail, and 64 laboratory experiments are delineated to provide a solid basis for developing the practical skills required in the many-faceted work of a conservator.

Hendricks, an acknowledged authority in the field of photograph conservation, and his associates have investigated and clarified many poorly understood or unknown causes of degradation of monochrome photographs and have devised appropriate restoration methods and procedures. This ongoing program has been carried out during the past 14 years with the involvement of more than 40 conservation trainees. The experience gained in the training of these conservators led to the conclusion that the following are the most important study areas:

• the history of photographs and photographic processes, the historical and artistic value of the photographs made by these processes and commonly found in collections, and their physical and chemical properties
• the application to photographs of conventional conservation techniques used for prints and drawings, such as cleaning, removal of tapes and adhesives, dismounting from acidic and brittle backings, and repairing torn or otherwise damaged images
• photographic sensitometry, i.e., the quantitative evaluation of the response of photographic films and papers to light exposure and chemical processing and the application of that knowledge to the preparation of accurate copies and duplicates of negatives and positives on transparent and opaque supports
• the application of scientific test methods developed in the photographic industry for evaluating the performance and aging characteristics of supports (glass, plastic film, paper), binding materials (albumen, collodion, gelatin), and image-forming substances (silver, metal salts, pigments, dyes)
• photographic chemistry as it applies to the restoration by chemical treatment of degraded photographic negatives and positives.

The organization and contents of the manual reflect this assessment. They also reflect the fact that the interns accepted by the Conservation Laboratory of the National Archives of Canada must have formal training in fine arts conservation, photographic technology, or chemistry. Consequently, the text and experiments are designed to fill gaps in knowledge and skills in these three areas. However, the success of even the most astute students will depend to a large extent on the guidance and support of a knowledgeable conservator, especially in the execution and analysis of the laboratory experiments. Students will also need access to the necessary equipment and laboratory facilities if they are to get the proper start in developing their practical skills. Others, including experienced conservators, also will profit from reading this guide or having it available as a valuable source of information on the topics covered in its 11 chapters. Moreover, the comprehensive literature references included at the end of each chapter and the special 30-page bibliography are an invaluable resource by themselves.

Plaudits are also in order for the clarity and technical accuracy of the text, the excellent typography, the quality of the numerous black-and-white and color illustrations, and the use of premium alkaline paper. The one serious deficiency is the cover and binding, which are much too frail for such a thick and heavy book, especially since the unusual format of the pages (8� in. � 10� in.) makes for extra stress on the spine. This shortcoming is particulary surprising in view of the high price and high quality of all other components.

There are more than 30 other publications that deal with various aspects of the preservation and care of photographs. These books can be very useful in identifying materials and selecting the best methods for dealing with specific types of age degradation. However, none has a broad enough scope to serve as a self-contained training manual, and none provides information on all the scientific test methods that have been developed for evaluating the performance of photographs. For these reasons, Fundamentals of Photograph Conservation is a unique and valuable publication, a fact that should become more apparent from the following review of its chapters.

Chapter 1, “Photographic Conservation Training Program,” includes an introduction describing the evolution and aims of the manual, an outline of its scope, a description of the bibliographic database called PHOCUS, and a bibliography of 14 basic reference books on the general history and science of photography, which are cited throughout the training manual. PHOCUS is a collection of more than 9,000 research articles and technical and historical books related to photographic conservation, gathered and managed by the National Library of Canada. About 6,500 of these references have been transferred to the Conservation Information Network and are available to its subscribers.

Chapter 2, “Darkroom and Laboratory Equipment and Procedures,” describes the equipment and procedures used in the archives' photograph conservation laboratory. The photographic studio equipment includes an impressive list of top-rated 35 mm and view cameras, lenses, lighting units, and copying equipment. The printing and processing equipment for films and papers is also first-class and includes a sensitometer for exposing processing control strips and a roller-transport and a rotary-drum processor for black-and-white and color films. Next, the makeup and functioning of contact and projection printers, the sensitometer, and the processing equipment and methods are explained.

This section is followed by a discussion of the materials testing equipment (stereo microscope, transmission-reflection densitometer) and the prints and drawings conservation equipment (suction table, tools, laboratory furniture, and analytical equipment). The concluding sections deal with chemical laboratory equipment, proper laboratory procedures, safety, and work habits. At the end are literature references.

Not many institutions or individuals have access to such a wide range of excellent equipment, but this fact does not diminish the value of knowing what is used in a leading institute devoted to the conservation of a very large collection of photographs.

Chapter 3, “Light-Sensitive Materials: Theory, Structure, and Deterioration Mechanisms,” deals only with silver-based products and processes (other historic imaging systems are covered in chapter 5). The first topic is photographic image formation, including discussions of printing-out and developing-out materials, chemical and physical development of exposed silver halide crystals, the filamentary structure of silver grains, the relation of image tone to particle morphology, and paper and film speed. The second topic is the laminate structure of contemporary photographic materials and the functions of each component, i.e., supports, image-forming layers, substratum, and back coatings. The third topic is the causes and mechanisms of mechanical and/or chemical degradation of supports, image-forming substances, and layer adhesion. Excellent diagrams, photomicrographs, and color photographs support the factual, succinct text. The only statement that has been rendered inaccurate since the writing of these sections concerns the stability of triacetate film supports. At that time cellulose triacetate films were projected to retain acceptable physical properties for at least 300 years, if kept under the then-recommended storage conditions of 21�C and 50% RH. However, more recent investigations have shown that under such conditions the “vinegar syndrome” (the formation of acetic acid) causes the onset of autocatalytic degradation in about 40 years and that the free acidity will double about every 5 years thereafter. (This problem and how to control it are discussed more fully in the review of the new IPI Storage Guide for Acetate Film, p.321).

Chapter 4, “Black-and-White Processing,” deals with more than just that topic, including sensitometry (the study of the response of photographic materials to light), densitometry (the measurement of the light absorbance of silver images), and methods for securing and evaluating the permanence of black-and-white photographs. The chapter also contains detailed instructions for 19 experiments. The clear explanations of the concepts and the step-by-step instructions for the experiments are exemplary, notwithstanding three statements that seem to be erroneous: (1) On page 71, “The total contrast of an original scene is closely related to the log exposure range produced on the film, but may be much greater due to flare.” Flare would have the opposite effect. (2) On page 96, the formula given for the preparation of a stock solution of D-72 developer yields 1 liter and not 500 ml of solution. (3) On page 114, item 8, Kodak Contrast Process Ortho and Kodalith Ortho, Type 3 films will not produce a gamma of about 1.0 when developed in D-11 for the recommended times.

Chapter 5, “Historical Photographic Processes,” is divided into two main sections. The first describes the most important historical processes, how to identify them, and their preservation requirements. A step-by-step procedure for arriving at the correct identification of a photograph is followed by well-illustrated descriptions of the structure and physical properties of the most popular monochrome and color photographs. The second section provides formulas and instructions for the preparation of six types of historic prints.

Chapter 6, “Duplication and Copying,” should be of interest to anyone wanting to learn technically sound procedures for reproducing original photographs on transparent or opaque support without loss in quality. These procedures require knowledge of sensitometry and processing acquired through the experiments described in chapter 4 and extension of that knowledge and experience by means of 18 additional experiments. These experiments cover such diverse subjects as construction of tone reproduction diagrams; evolution of condenser and diffusion enlargers; copying of daguerreotypes, ambrotypes, and tintypes; and corrective duplication and printing of stained historical negatives.

Chapter 7, “Paper Conservation Treatments as Applied to Photographs: A Review,” encompasses well-illustrated discussions of 16 treatments, including dry and wet surface cleaning; removal of photographs from mounts; washing of prints and mounts; application of new backing or support and encapsulation; repair of cracked and lifting emulsion layers; emulsion transfer; repair of broken glass-plate negatives; and treatment of photographs in cases.

Three points are made very strongly and properly: (1) The conservation techniques developed for conventional prints and drawings often require significant modification when applied to photographs, owing to their laminate structure and the special properties of the image and auxiliary layers and supports. (2) Many of the techniques require a high degree of manual skill that can be learned only through considerable practice, supervised by a trained conservator. (3) Careful assessment is an indispensable first step in the selection of a particular treatment. The expertise required for making such a selection can be gained only through extensive study of professional literature and examination of many specimens of the various processes. The first of these requirements can be met by perusing the extensive list of literature references and supplemental readings given at the conclusion of the chapter.

Chapter 8, “Chemical Treatments,” starts with a warning that chemical treatment of deteriorated photographic images is a controversial issue among conservators, photographers, dealers, and collectors, since little is known about the effects of various chemical treatments proposed and used for silver-based images. Two of the contentious questions are: How significant are the proposed changes to the integrity of the photograph? Does the potential loss through continuing deterioration justify the risks involved? In any event, if the decision is made to use chemical treatment, two preliminary actions are recommended: (1) The original photograph should be duplicated (transparency) or copied (opaque support), and (2) if a border can be clipped, it should be treated with the selected chemicals to check their safety. However, it must be understood that even a positive result does not assure that the same treatment will not damage or even destroy some or all of the image.

The specific image treatment methods described in detail are intensification, reduction, and bleach and redevelopment. Formulas and procedures for these three kinds of treatment are given in the instructions for eight experiments.

Chapter 9, “Preservation, Storage, and Display of Photographs,” contains a great deal of technical and practical information about the many factors that can affect the stability of photographs. The specific factors examined in the discussion of storage conditions are the environment (temperature, relative humidity, air quality, and illumination); cold storage; and filling enclosures. The next section addresses the need for proper handling and identification of photographs. Emergency and disaster preparedness procedures for different types of photographs are described in the fourth section, with heavy emphasis on how to deal with water immersion, because it is the most frequent disaster. Two very useful tables summarize the recommended priorities, precautions, procedures, and drying methods for all types of black-and-white and color photographs. The last three sections provide instructions for three experiments related to the effects of moisture and water damage, and to discussions of display conditions and of American National Standards Institute (ANSI) standards that deal with the stability and storage of black-and-white and color photographs.

Chapter 10, “Tests for Image Stability and Suitability of Conservation Materials,” includes 10 tests, almost all of which were developed or adapted by ANSI committees that develop standards for photographic materials. Five of these tests deal with image stability of black-and-white and color photographs (accelerated dark aging, light fading, and gas fading); four with physical stability of gelatin image layers (melting point, swelling, scratch resistance of dry and wet layers); and one with the evaluation of the suitability of materials used in storage and conservation. It should be noted that these standards have been revised since the preparation of the guide; for instance, the new standard ANSI IT9.9-1990, Methods for Measuring the Stability of Color Photographic Images, prescribes a multitemperature Arrhenius-type test method for determining the dark stability of dye images and tests with different types of illumination for determining their stability under various display conditions.

Chapter 11, “Condition Reports, Treatment Proposals, and Collection Preservation Surveys,” addresses the need for documentation of all photographic conservation work.

Photographs taken before, during, and after treatment should always be a permanent part of the records describing an individual specimen, the results of the examination, and the analysis and assessment of damage. Proposed treatment should be developed in consultation with the curatorial staff. Suitable forms for a combination condition report and treatment proposal are included.

The range of information needed for a preservation survey report of large collections is examined in the second section. This information includes an account of the acquisition status and use of the photographs; a description of the contents of the collection; the different types and number of photographs; the range of sizes; the present storage conditions; available identifying information; type and severity of damage; storage materials and formats preferred by the curator; needed preservation supplies; storage requirements; feasible preservation options; and estimated staff time required for implementation of recommended preservation measures.

The importance of the physical and chemical properties of the support of photographs to their proper functioning at all stages of their life cycle is often overlooked, because attention normally is focused on the stability of the image and its components. It is only when certain deficiencies of the support threaten the quality of the image or the safety or longevity of the photograph that the probable impact and control of these deficiencies receive due consideration. A case in point is the gradual but inexorable chemical decomposition of cellulose acetate film base and its effects on the integrity of the film record. The rate of this degradation, like most chemical reactions, is greatly influenced by storage temperature and relative humidity. This effect has been known and documented for decades, but very few film collections have been kept under recommended environmental conditions. It was not surprising, therefore, that recent surveys of collections (Horvath 1987) show that nearly every sizable collection of films contains significant numbers of deteriorated acetate-base specimens. What's worse, accelerated aging tests carried out at Image Permanence Institute (IPI) as part of a research project funded by the National Endowment for the Humanities (NEH), National Historical Publications and Records Commission (NHPRC), and Kodak indicate that the onset of rapid deterioration of acetate-base films stored under the recommended 21�C and 50% RH condition is only about 40 years. The causes of the initially slow and subsequent rapid rate of acetate-base film deterioration have been elucidated in several reports on investigations carried out during the past few years at the Manchester (U.K.) Polytechnic Institute and the Kodak Research Laboratories (Edge et al. 1989; Allen et al 1988; Ram 1990).

Chemical deterioration of cellulose acetate-type film is now known as the “vinegar syndrome” because the earliest obvious symptom of this problem is a vinegarlike odor caused by the liberation of free acetic acid. As the base degradation continues past this point and more and more acetic acid is generated, shrinking, buckling, and embrittlement render the film progressively impaired. The IPI Storage Guide for Acetate Film explains the relationship between the “vinegar syndrome” and temperature and relative humidity and provides an overview of the film storage requirements for minimizing the rate of degradation. Therefore, the guide should prove a great help to collections managers for evaluating the quality of the storage environment for their film and for determining the best affordable option for extending the useful life of the majority of specimens.

This guide, a well-illustrated booklet plus a separate wheel, graph, and table, is distinguished not only by the value of its contents but also by being the most readable, well-organized, and practical guide I have encountered in years. Based on the data presented in the four units one can predict the time required for the onset and progression of the vinegar syndrome under various storage conditions. The booklet explains what the guide is and what it is not, describes the design and use of the wheel, graphs, and table, and discusses the causes and manifestations of acetate-base deterioration, strategies for storage of degrading films, and the general philosophy of film storage. The bottom line of this instructive discourse is: “In order to control chemical deterioration of film, make the temperature as low as possible, and keep the average RH between 20% and 30%.” However, available equipment, location, and the presence of other kinds of products in the storage area may make it necessary to operate at a higher RH. In that event, values up to 50% can be used without catastrophic consequences, albeit at an increase in the rate of acid generation and of associated dye fading in the case of many color films.

The wheel has two sides. One shows the approximate number of years required for the onset of the rapid phase of degradation of fresh acetate film, the time at which free acidity reaches 0.5. (Free acidity is not the same as pH. It refers to the total amount of acid in the film base, which is determined by the volume of alkali required for neutralization.) The other side shows the approximate number of years it would take for a film that has already reached 0.5 acidity to reach an acidity level of 1.0 under various storage conditions. With this wheel it is easy to compare the rates of deterioration under a wide range of conditions and to determine which of several existing storage environments is best or to consider the various combinations of temperature and RH that would yield a specified life expectancy.

The two graphs, printed on opposite sides of a 8� in � 11 in. durable card, are time contours for the vinegar syndrome in degrees Fahrenheit on one side and Celsius on the other. They show at a glance the relationship between temperature, RH, and the time in years for fresh film to reach 0.5 acidity at various constant conditions; e.g., about 100 years of life expectancy could be obtained at 70�F and 20%RH, at 48�F and 80% RH, or any of the intermediate combinations.

The table, printed on a second 8� in � 11 in. card, is titled “Time out of Storage.” It embodies an approach first suggested by Mark McCormick-Goodhardt of the Smithsonian's Conservation Analytical Laboratory, that shows how film life expectancy is affected by removal from a storage vault and use at room temperature for a period of time. This particular table lists the predicted times in years for acetate-base films to reach 0.5 acidity when kept out of a storage vault for 0, 1, 5, 10, 30, 90, and 120 days at 75�F and 60% RH, when the vault conditions are 20%, 40%, or 60% RH and 21�, 16�, 10�, 4�, −1�, −9�, −18�, or −26�C (70� to 115�F). Perusal of this table would show that a fresh film stored without interruption at 40�F and 40% RH would reach the onset of the vinegar syndrome in about 450 years, but that 30 days out of storage in 75�F and 60% RH would reduce 450 years to about 175 years, and 90 days to 70 years.

REFERENCES

Allen, N. S. et al. 1988. Degradation of historic cellulose triacetate cinematographic film: Influence of various film parameters and prediction of archival life.Journal of Photographic Science36:194–98.

Edge, M. et al. 1989. Fundamental aspects of the degradation of cellulose triacetate base cinematograph film. Polymer Degradation and Stability25:345–62.

Horvath, D. G.1987. The acetate negative survey. Kentucky, Ekstrom Library, University of Louisville.

Ram, A. T.1990. Archival preservation of photographic films: A perspective. Polymer Degradation and Stability29:3–29.

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