OPTICAL BRIGHTENING AGENTS IN PHOTOGRAPHIC PAPER
Paul Messier, Valerie Baas, Diane Tafilowski, & Lauren Varga
For the past several years, the use of optical brightening agents in photographic papers has increasingly attracted the attention of conservators, curators, art dealers, and collectors. For the most part, this recent notice stems from the use of optical brightening agents for dating photographs. When present, optical brightening agents are usually easy to detect, as the compounds produce a distinct cool, blue-white fluorescence when exposed to near-ultraviolet radiation. Based on papermaking literature, sources within the photography industry, and the examination of reference collections of known provenance, the start date for the incorporation of optical brightening agents in photographic papers is generally held to be the mid-1950s. Within the last several years two major authenticity scandals, involving images by Man Ray (1890–1976) and Lewis Hine (1874–1940), were sparked when prints that purportedly dated from the 1920s and 1930s were found to incorporate optical brightening agents and other materials-based anachronisms (Falkenstein 2000; Woodward 2003).
Indications pointing to the mid-1950s as the industry start date for the incorporation of optical brighteners are strong though largely undocumented. Persons associated with the photographic industry have consistently maintained that the use of brighteners began in the 1950s and increased rapidly throughout the 1960s. This same period is also cited for the introduction of optical brighteners for the wider papermaking industry (Browning 1977). While research into fluorescent additives dates from the late 1920s, there is evidence to suggest that it was not until the introduction of dyes based on the compound stilbene, in the early 1940s, that a method for industrial-scale fluorescent brightening of paper and textiles seemed practical (Mustalish 2000). For example, present and former Kodak staff members independently cite an internal report from February 1951 that proposed the use of optical brightening agents and estimate that the earliest commercial application of brighteners did not occur until the mid-1950s (Warner 1999;Valvo 1999). This report by the Paper Service Division at Kodak describes a survey under way as early as 1949 in which papers treated with a fluorescent dye identified as “Pontamine White BR” were compared by “professional and amateur examiners” to determine preferences (Kodak Paper Service Division 1951). The primary finding of the survey is that the general preference among those surveyed was for nonbrightened paper. For this reason, the report concludes, “The use of fluorescent dyes for the brightening of this type of photographic paper is therefore not recommended” (p. 2). While this document helps date an industry leader's interest in brighteners, left unclear is when Kodak disregarded the recommendation in the report and began using brighteners. Proprietary and otherwise confidential reports documenting the analysis of prints attributed to Man Ray and Lewis Hine by Agfa materials research staff indicate the company began using brighteners in its papers during the late 1950s. Independent of this work, other staff at Agfa also point to the late 1950s as the starting point for the use of optical brightening agents (Auer 1999). This manufacturer information is supported by occasional collections surveys. One such survey comprised 39 photographs accessioned by the Metropolitan Museum of Art between 1940 and 1960 (Murphy 2001). In this survey the first positive observation of optical brighteners occurred in prints accessioned in 1956.
According to Kodak staff, while brighteners can be integrated into paper raw stock, emulsions, baryta, and processing chemicals, the more recent trend is to apply brighteners as a surface coating, which is more effective and economical (Gray 1999). This same source indicates that brighteners added to pulp, in the wet end of a Foudrinier machine, can result in a speckled fluorescence of the paper base (observed with near-ultraviolet radiation), as different fibers in the pulp have variable degrees of dye absorption. An industry source from Ciba Specialty Chemical Corporation stated that while there are presently many specialized uses for optical brightening agents and while many different companies all over the world manufacture these compounds, brighteners are still mostly based on the stilbene molecule (Cheek 1999).
Though this evidence carries significant weight, there is still no definitive primary source indicating when the photographic industry began incorporating optical brightening agents (Mustalish 2000). The purpose of this study was to test and supplement this existing body of evidence by developing an authoritative baseline documenting the use of optical brightening agents in 20th-century photographic papers.