Today in lab, I did a little bit of testing trying to resolve some questions I have had about my photograph. The main question I have is what type of photograph is it. In one of the many source I have read, I got a lot of useful information. And I narrowed the search to three manufacturing processes: the albumen print, the printing-out print (POP), and the gelatin silver developing-out print. One way I decided to determine the information needed was to perform an x-ray fluorescence (XRF) analysis. This technique shoots a laser beam into the first millimeters of a surface and records the energy released when the beam hits the different chemical compounds. The resulting graph gives peaks at the elements that are found in the layers. I had narrowed my options down to three options, and this only by sight identification. The XRF confirmed my hypothesis and showed a large peak in the Barium region, and smaller peaks at Sulfur, Strontium, and Silver. All of which are characteristic of the POP and Gelatin Silver Developing -out Print, based on the chemical composition of the printing paper and the emulsion. Using a microscope and looking at the photograph I debated between the two, but found characteristic microscopic cracks and scratches in the surface. This pointed to POP as it is more sensitive to surface damage such as cracks and scratching than the gelatin process. Therefore, I now know the chemical makeup of the emulsion layer and also what time period the photograph was made in, between the 1890s-1940s (when this process was most popular).
Also today, I took UV photographs (which I will upload tomorrow). From the UV images I was able to determine what the brown spots on the back of the image were. According to one of my instructors, foxing, which is simply mould, or ferrous hydroxide, which is the metal salt inclusions in the paper that upon oxidation produce brown spots, are different things and have different reactions to UV light. With the photograph I was able to determine that both were present. Under UV, foxing will fluoresce and ferrous hydroxide will show black. Both result in the increased acidity of the paper. Therefore, from here on out, I will need to test the paper in different areas to determine the acidity, and, if it is acidic enough, decide what deacidification process will be used, of which there are many.