Abstract
One of the techniques for making photographic negatives most used in the history of photography were gelatin glass plates. This technique was used not only in the artistic field but also and mainly in the scientific field. The main period when glass plate negatives were used in astronomy was between 1890–1980. There are over 7 million of these negatives all over the word and they carry valuable historical scientific data. However, during the long-term storage of this material, deterioration of the emulsion (picture) layer and/or the support (glass) layer has occurred. In this paper we report on our preliminary results from an analysis of the yellowing of the emulsion layer and of gold micro-spots. Both phenomena worsen the readability of the information in the photograph, and it is necessary to prevent their formation, which is why we need to know as much as possible about their origin.
Highlights
As it is visible from the observation of photographs of samples, there are two main symptoms of deterioration of the emulsion layer: (1.) yellowing inside the emulsion layer (Fig. 1); (2.) surface golden spot (Figs. 2 and 3)
After this point the concentration increased for one point to a slowly decreasing one. This pattern occurred for all golden spots and made appearance of the sphere. These results suggested that the golden spot disease in the surface of the emulsion layer is formed by silver sulphate (Ag2S)
We examined a set of glass plate negatives using chemico-analytical tools such as Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy and SEM/EDS
Summary
The first stable technique of preparing negatives on paper was investigated by Henry Fox Talbot in 1841. In this process the paper was waxed to obtain a transparent material for copying the image. This waxing made paper negatives unstable and that is why they were not so popular. The first glass negatives were used 6 years later by Niépce de Saint Victor. His negative system used chemicals which were almost similar to those used nowadays in negative process: halogens (KBr, KI, NH4Br a NH4I), nitrate of silver with acetic acid and gallic acid for developing the image. That is why the egg albumen negative system was not very popular, and in 1851 egg albumen was replaced by collodion. [2]
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