Actually, paper emulsions can be just as complex as film emulsions when undergoing finishing. The reason is the exacting control of curve shape and fog, and also for keeping.

The liquid emulsions do caution you to be careful as after each heating they may change. This is a sign of "old style" finishes using just sulfur or sulfur + gold.

However, many paper emulsions were never finished at all. They were made in such a way that they gave the right characteristics right out of the "pot".