Emulsions are now made in huge batches by using automated equipment. Everything is controlled to the precise flow rate, temperature, time, and mixing rate (rpms and combined flows as well as adjusting turbulence during mixing). This is done under dim red light and sometimes with IR goggles.
Coating is done at precise rates in flow and throughput of support with carefully regulated chemicals.
The chemistry used involves up to 9,000 ingredients or more in one color film, all of which are tested for impurities before use, and the final products are tested at every stage of the operation. The emulsion is tested before coating and the coating is tested after the emulsion is dry.
I could go on, but only Kodak, Fuj and Ilford have the rigid specs for this fully worked out. All other companies use less rigorous methods. The one exception is the remnant of Agfa. Agfa once had the same standards and the remaining Agfa operations have been able to maintain most all of them.