Older emulsion technology involved the addition of silver to halide or silver in ammonia added to halide. At EK, we called these SR and SRAD emulsions (single run and single run ammonia digest).

Basically, they used active gelatins, or gelatins that reacted with silver halide during the making procedure, whereas modern emulsions use inert or oxidized gelatins.

The old emulsions simply requred the addition of silver in a big dump to the halide. In fact, the German word for the addition was 'gekipped' or dumped or tipped in English. Hardly a controlled addition, but it typifies early emulsions.

The precipitation and finish or chemical sensitization alll took place at the same time.

This was followed by noodle washing or chopping the emulsion into noodles or cubes and then washing in distilled water or salted water.

The difference between this and the ultrafiltration is that these emulsions become more dilute during washing but the ultrafiltered modern emulsions can be made more concentrated during washing.

Between these early emulsions and the modern emulsions, there was a period in which emulsions were washed by coagulation using a special type of gelatin called Phthalated Gelatin.

More to come.

PE