Trying to find relevant sources of information for the surface relief properties of gelatin, Paul A. Lehman finds an unusual source to find answers: The patent archives. He shares his findings here. Each patent provides detailed information on emulsion ingredients, preparation and processes, which can be reproduced in a suitable home darkroom laboratory.
Color and Gelatin Relief Emulsions U.S. Patents Issued to Michele Martinez
Modern day availability of information via the internet is amazing. For example, doing a search for “silver gelatin” generates over 13,000,000 hits. Unfortunately, if one is looking for a particular or specific detail, it would be impossible to examine each hit for relevance.
“With little assurance of value to the intent of the search to review at 30 sec/hit, it would take about 50 yrs to complete the examination.”
The consequence is that valuable information can be lost in the noise of those millions of hits. Two alternatives are available, multiple creative word selection for focusing the search, or finding a web site that is known and limited to contain relatable information (such as www.AlternativePhotography.com for photographic processes, or http://camera-wiki.org for vintage camera information, for two examples).
In doing research to investigate the surface relief properties of gelatin, as found with the Carbon Print process, I found a source of information in the U.S. Patent archives. From a search of these archives, several interesting patents were found, relating to color and gelatin emulsions, issued to Michele Martinez of London, England. The PDF document links to the patents are provided below.
| Reference | Patent Name | Patent Number | Issue Date |
| Photographic iron-silver color process | 2,886,435 | 1959-05-12 | |
| Light sensitive color element | 2,284,877 | 1942-06-02 | |
| Photographically produced gelatin relief | 1,954,325 | 1934-04-10 | |
| Photographically sensitive element | 1,994,293 | 1934-01-23 | |
| Color-photography | 1.910,117 | 1933-05-23 |
Source: https://ppubs.uspto.gov/pubwebapp/static/pages/ppubsbasic.html
Each patent provides detailed information on emulsion ingredients, preparation and processes, which can likely be reproduced in a suitable home darkroom laboratory by someone with experience in alternative photographic processes. Unfortunately, I have not had an opportunity (yet) to try any of these processes.
No further information on Michele Martinez has been found at this time, other than an association with A.H. JOHNSON & Co. (PAPER) LIMITED, of London, England (c1929), Eastman Kodak Company, Rochester, N.Y. (c1941), and with Panacolor, Inc., Los Angeles, CA (c1953).
For those interested in color photography, or the potential value of gelatin relief produced from a photographic image, these patents may prove interesting.
Color Photography, Patent # 1,910,117, 1933 Pdf
This patent describes an emulsion surface which will yield a picture in one or more colors in accordance with the wave length of the incident light. Key components of the emulsion include Ferric ammonium oxalate, Oxalic acid, Ferric ammonium citrate, and Tartaric acid, to name a few. Development uses Sodium thiosulphate, Ammonium carbonate and Potassium ferricyanide. Explanatory figures are included.
Photographically Sensitive Element, Patent # 1,944,293, 1934 Pdf
This patent provides information on a light sensitive emulsion useful in producing images in relief for photographic, photo-mechanical and other purposes. One example emulsion (of several provided) contains Gelatin, Ferric ammonium citrate, and Oxalic acid. Following exposure, development is by heating to 90– 120oº C. An explanatory figure is included.
Photographically Produced Gelatin Relief, Patent # 1,954,325, 1934 Pdf
This patent is very similar in text to the above patent #1,944,293, presenting additional procedural and emulsion information, and expanded descriptive usefulness of this emulsion. Explanatory figures are included.
Light sensitive color element, Patent # 2,284,877, 1942 Pdf
This patent provides information for color photography using color formers and resins in a common volatile solvent. Descriptions of five different example gelatin based emulsions are provided for consideration. An explanatory figure is included.
Photographic iron-silver color process, Patent # 2,886,435, 1959 Pdf
The patent provides information for the photographic production of monochrome and polychrome pictures by means of light sensitive ferric salt layers. Silver salts are utilized in the formation of silver images, being afterwards transformed or converted into colored compounds or used to form colored compounds by way of accessory reactions. The patent holder explains that “one object of the invention is to provide an inexpensive, simple, rapid and fool-proof method of color picture production”.
Conclusion
Interestingly, at the time of date patent issue, these methods, in today’s terminology, would be considered alternative photographic processes. Here we are today, re-considering them as revived alternative photographic processes. Finding these patents also suggests that there may be many more interesting or unusual photographic processes hidden within the archives of the U.S. Patent Office, worthy of exploration (https://www.uspto.gov/patents/search).
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Interesting. in Photographically sensitive element #1,994,293 is similar to another process. The FAC and OA ratio is the same but there is less gelatine. When exposed to UV light, the FAC “readies” the gelatine to crosslink into polymer chains in a low ph environment. When an oxidiser is added this makes the gelatine insoluble in water (and anything trapped in the gelatine, such as pigment). The acid, unused FAC and gelatine get washed away.
So, is the heat also causing this crosslinking and the trapping of carbon monoxide as part of the needed oxidizer?