Photographic gelatin

Photographic gelatin

One of the materials the most important for the collotype is the gelatin. It establishes the photosensitive stump which is going to be transformed into coat printer. Once moistened, it will push away the ink in the parts not insolated, and will hold it in the parts establishing the image. For the collotype, it is mainly it which is the object of quite attentions, confirming the delicacy of this substance.

Photographic gelatin

Concerning the manufacturing, there are two main methods, the acid processing and the alkaline processing. In both cases it is about a substance made from bone of animals, skins of veal and porks.

Gelatins used for the collotype are gelatins of type B, realized by the alkaline processing. The raw material is immersed in a whitewash with ambient temperature, periodically renewed (we use hydroxide of calcium Ca(OH)2 called also some whitewash or slaked lime). It is about a long processing ( several weeks) justifying the high cost of these gelatins, with regard to the short processing of gelatins by acid processing.

A more recent process, the enzymatic processing, allows a quasi-total degreasing in the raw material, and to obtain gelatins of very high quality.

Photographic gelatin
Photographic gelatin

Naturally, in case of difficulties in prosecutor of photographic gelatins typifies B, we would be tried to use the other technical said gelatins (they are not either gelatins food), but they do not also suit for the collotype because too subject to the inflation in the water. Those used to realize photographic emulsions possess performances completely adapted for the use of the collotype, and are perfectly dry-cleaned. With this type of gelatins, the addition of fish glue which is evoked in the ancient works, to increase the hardness, is not any more justified. It was it formerly when gelatins employees were softer.

What interests us here, it is to know in which conditions it is used for collotype. We are going to review all the stages of the preparation of the gelatin to realize the photosensitive coat which is going to serve as matrix for printings.

Collotype Shop Several hardness of photographic gelatins are for sale in the Collotype Shop.