Quote Originally Posted by desertrat
Can an active gelatin be made from the gelatins we can get today? I'm guessing it would be very difficult, but I'm curious how it would be done.
No, it cannot be done.

The active part has been removed (oxidized generally) from the emulsion. It is also a variable quantity from batch to batch of raw gelatin. We used to used what were termed Hard, Medium and Soft grades of active gelatin to achieve the various speeds and contrast grades. That is now achieved in a precise manner by addition of an exact quantity of an active sulfur compound such as was removed from the gelatin.

The original component was allyl thiourea.