The infirmities are worrying. After nitrate film stock proved hazardous, a compound called cellulose acetate became, in the nineteen-forties, the medium in which microphotographers placed their faith. At the National Bureau of Standards, experimenters baked samples of it in an oven, tested them for residual strength (the research was subsidized7 by “several manufacturers of photographic films and equipment”), and declared that “cellulose acetate motion-picture film8 appears to be very promising for permanent records.” Charles Z. Case, of Recordak, seized on this wishful governmental verdict, assuring library administrators (some of whom didn’t need much convincing) that his company’s product was “in the same category of permanence9 as the finest book-papers.”
But acetate has a way of releasing (or “off-gassing,” to use the conservator’s term) the acetic acid employed in its manufacture; as the decades pass, afflicted microfilms can begin to shrink, buckle, bubble,10 or stick together in a solid illegible lump. Responding to what a former chief of microforms at the New York Public Library called “the dreaded vinegar syndrome”11—so named for its sinus-clearing smell — the industry switched, by the mid-eighties,12 from acetate to rip-resistant polyester. (Polyester-base film was developed by Kodak in the early sixties, in part to solve problems encountered by the CIA’s Corona spy satellites:13 the acetate film tore in orbit.) Millions of rolls of acetate images14 remain in libraries; indeed, a sizable portion of the preservation budget in some large institutions now must go toward the reduplication, with an attendant loss of detail, of old micro-negatives or positive prints onto fresh polyester.
Better plastic doesn’t solve all the problems, either, since microfilm’s emulsion — the soft layer of gelatin and silver that holds the image — has vulnerabilities as well. In the early sixties, there were reports of strange spots15—some yellow, some red, some with concentric rings — that had developed in the master negatives of collections at the National Archives. In response, inspectors from the National Bureau of Standards examined thousands of rolls of government microfilm; they found “a widespread incidence of defects.” The General Services Administration issued Circular No. 326 in 1964 to all heads of federal agencies warning of the spots (I found it filed in Verner Clapp’s papers at the Library of Congress) and developed a half-day workshop covering “blemish recognition, inspection techniques, and reporting procedures.” No remedy was proffered, because none was known. Still, the GSA quoted the Bureau of Standards report’s reassurance that “from the practical point of view, no information has been lost.”
This bad news simmered for some years, and manufacturers in the meantime promoted two varieties of non-silver microfilm: vesicular film, whose image results from the heating of polyester until it forms tiny light-absorbing bubbles; and diazo film, which uses a dye made of diazonium salts on exposure to ammonia. Both vesicular and diazo films are cheaper than silver film. But in the early seventies, some librarians were distressed to discover that texts reproduced on “Kalvar”-brand vesicular film had been releasing hydrogen-chloride gas, which (according to Susan Cates Dodson in Microform Review) “attacked metal filing cabinets,16 and reduced the boxes the film came in to dust.” The corrosiveness was confined to one formula of film, but all vesiculars proved to be heat sensitive — their tiny gas bubbles begin to collapse above 170 degrees, and above 175 degrees (wrote Carl M. Spaulding, a program officer with the Council on Library Resources, in 1978) “even the most heat-resistant [vesicular films] will suddenly suffer complete image loss.”17 Dodson measured the temperature18 of the glass film gates of common microfilm readers and found that some reached 180 degrees.
Diazo microfilm, on the other hand, though relatively cheap, is prone to fading on exposure to the light of the reading machine. (It fades in the dark, too, but more slowly.) One piece of research from 1978 found that a frame of diazo film would be likely to suffer serious light-damage19 after three and a half to twenty hours of use, depending on the brand of film. Major historical dates on diazo — Lincoln’s assassination, say, or the moon landing — could rack up enough exposure time to fade away, while frames nearby might still retain good contrast; if somebody left a reader on over a weekend with film in it, that might be the end of the image.
Traditional silver-grained emulsions held up better than that, at least — or did they? Word was getting around that certain species of fungi20 found nourishment in the film’s soft (and easily scratched21) gelatin. In his 1978 article, Carl Spaulding wrote that “the extreme susceptibility22 of silver film to severe damage from water or high humidity is a major concern of micrographics professionals — although relatively unknown to most librarians.” Librarians are more aware of the problem now: in 1991, a check of master negatives23 at the University of Florida’s P. K. Yonge Library of Florida History (whose microfilm collection includes “the only extant copy of many Florida newspapers”) found that more than half had fungal troubles.
More ill news arrived from the Public Archives of Canada in 1981; a small study there determined that thirty-five percent of a sample of rolls of silver microfilm had “redox blemishes”; five percent of these “revealed a loss of information.” In 1988, a group of scientists at the Image Permanence Institute in Rochester, New York, wrote that “there seems to be a much wider24 scale ‘redox blemish’ problem in library and archive microfilm collections than is generally believed”; more than twenty percent of the half-million rolls in the Illinois State Archives were affected, for example. And there remained the chronic problems with residual hypo — leftover image-fixing chemicals that weren’t rinsed away during the processing of the print or the master. Verner Clapp had himself written about the fading caused by unwashed hypo in a squirmy 1954 Library Journal piece called “Are Your Microfilms Deteriorating Acceptably?” The original draft25 of the article, preserved in Clapp’s papers, has the following passage, cut from the published version: “It is horrifying to calculate what the cost of testing, handling, and possible rewashing will be if applied to the entire LC collection of microfilm, now amounting to approximately 100,000 reels. Yet this precaution is indicated.”
As a result of Clapp’s article, the Library of Congress began a small-scale program of sampling bought microfilm, mostly of newspapers, for “excessive residual hypo,26 and other defects related to definition or legibility.” Between 1972 and 1976 the evaluators rejected, on average, half of the items tested — a “shocking statistic,” according to the chief of the Library of Congress’s Order Division in that period. Yet so eager were the library’s managers to reduce the size of the newspaper collection that “in more than 50 percent27 of these cases the film rejected by the laboratory is not returned to the vendor but is accepted for addition to the collections”—which is to say that the library knowingly accepted film that wasn’t good in order to replace original newsprint that was. And the laboratory’s sample during this period was only 0.7 percent of the library’s incoming spoolage; the rest passed through unexamined. (Turning disbound pages under a camera day after day is a tedious, trance-inducing job,28 but checking each frame for mistakes is even worse.)