Agfacolor Neu - History of modern color film (part 3)

These are Gustav Wilmanns and Wilhelm Schneider, both chemists working for IG Farben, which had then pooled all their photo activities under the umbrella of its department Agfa. Since 1922 Wilmanns was head of the manufacturing department at the photo site ("Filmfabrik") Wolfen (district Bitterfeld, Germany) and since 1928 in addition responsible for the central scientific laboratory of  Agfa and Schneider's boss. Since 1929 Wilhelm Schneider's main task was the development of black and white films, especially he worked on anti-halation backings. In 1932 he discovered  that specific dyes mixed into gelatin layers can't be washed out if they carry chemical groups that were known from cotton dyeing. With that he almost solved a 20 year old problem, which prevented the technical implementation of Rudolf Fischer's invention of the chromogenic multilayer color film
On April 11th, 1935 Wilmanns and Schneider filed for a patent (DRP 746 135).  Only a few days later they were overtaken by the Kodachrome film, which was launched on the market in the US on April 15th. However, it solved the problem of unwanted dye diffusion quite differently. It's easy to imagine that this was the starting point of a scientific and commercial race between the Wolfen team and the group in Rochester. For the following years Willmann's group grew to over 50 employees and probably the Rochester had a similar size. The battle was even fought on the legal field. Kodak laid an objection against the Agfa patent that ended with a settlement and had the consequence that it was granted not before December 23rd, 1943. A second patent ( DRP 725872 dated August 8, 1935 ) describes a further improvement in preventing the diffusion and laid the foundation for the "Agfacolor Neu" film. 
Figure from "film production", brochure of VEB Filmfabrik Wolfen (ORWO), GDR 1981

With this new color-couplers Agfa realized more or less exactly what Rudolf Fischer had in mind: Just one color developer was used for all three color layers at the same time to generate the desired dyes. This results of course in a  relatively simple film processing, which comprises only 5 steps to generate a positive image (reversal film), in contrast to the Kodachrome process with 27 steps. The diffusion resistance was due to the long alkyl side chains attached to the color couplers. Schneider and his colleagues at the time explained the effect with the entanglement of the long chains with the polymer structures of the gelatin. Today it is known, however, that the color coupler by their long tails form micelles, which by their mere size have a reduced diffusion rate. Well, as long as it works... 
During spring of 1936 the first successful pilot plant trials have been made. Some photographers used the new material on a trial basis at the Olympic Games in Berlin in August, although the sensitivity of only about 7/10 °DIN (today: 5 ISO ) didn't allow images of moving athletes. In November 1936, the first 135 cartridges were launched on the market (for RM 3.60, which is 10 Pfennig per shot). In the coming years, as did Kodak Agfa optimized method and recipes even further. E.g. in 1938 it was possible to increase the sensitivity to 15/10 °DIN (today: 25 ISO) by the addition of about 10 μg Gold Rhodanide (AuSCN) per film.

The Agfacolor process of course has been continuously improved over time and supposedly was protected by 278 patents. With the end of WWII in 1945 the Agfacolor methods and recipes were declared public domain. Many companies such as Adox, Ferrania, Fuji , Gevaert , Konica , Tellko, and Valca adopted the procedures. Here you can see some of the available film boxes. Kodak never used the Agfacolor method, as in 1937 they found another technical solution to avoid the diffusion problem with the color couplers. A corresponding film has been provided to the U.S. military in 1941. However, this is the topic of part no. 4 of this series, coming soon.

Other parts of this little history series...
1) Invention of the chromogenic film by Rudolph Fischer (English, German)
2) Kodachrome (English, German)
3) Agfacolor Neu - This post in German
4) Ektachrome and Kodacolor (English, German)

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