Old vs Early new, vs New
Old emulsion technology dumped Silver Nitrate or Silver Nitrate + Ammonia into a pot of active gelatin + a salt mixture. This was heated from 1 hour to 2 days at temperatures from 40 - 90 deg C (the 2 day 90 deg emulsions were called BOILED emulsions). The gelatin was active gelatin and the sulfur sensitization came from the gelatin. There were as many as 3 grades of gelatin for this type of treatment. The wash was essentially the last step.
In the 40s - 60s, the gelatin was inactive, and the addition rate was timed at a given speed. Temperatures were 40 - 60 deg C, and sulfur sensititization or sulfur + gold took place after the wash was complete.
After the 60s, emulsions used inactive gelatin, precise flow rates, measured vAg, and precise steps for digestion, ripening, and other addition steps. I have given the steps elsewhere but I include them below:
1. Nuceation - the preparation of the small seeds on which the emulsion is built.
2. Ripening and dilution - the step at which an emulsion is diluted to the optimum gelatin content and vAg. It is held to adjust grain size and composition. *
3. Digestion - the step at which a silver halide solvent is added to modify crystal shape and size. It is held to allow this to take place. *
4. Growth - the step at which more silver and salt are added in a linear or quadratic fashion. Any modifiers may be added here.
5. Hmmm, IDK what to call this, but here the vAg is adjusted by adding silver and salt to the optimum point for grain size, halide content and vAg.
7. Sulfur or sulfur + gold sensitization.
* = optional step.
I hope this clarifies how complex things can be (as if adding complexity can clarify anything )