Originally Posted by JOSarff
No one has addressed a "proper" or modern Cl/Br emulsion. All texts give plenty of examples of simple Cl/Br emulsions but they have absolutely no idea of what they are really making.
Regarding what Kirk says in his post, this is a matter of the solubility of each of the Silver salts and as such is very complex. I can just say simple that if you mix 10% Iodide with 90% Bromide you get a 10/90 Br/I and I can add that most all of that Iodide will be in the center unless it is double run or you use a silver halide solvent for digestion. But, with a Cl/Br there is little differentiation unless you use a double run, and even then the rules are rather strict!
I hate to get into that much chemistry in the book. If you follow an existing formula, you will get a pretty much repeatable result and reasonable curve shape and speed, but you will not know - really know, what you have made. I avoid them to avoid the complex chemistry. Kirk, a chemist, would love to see the chemistry! I know he might be the only person who would follow it though. Maybe 2 or three others.
I might add that Sulfur sensitization of Cl and Cl/Br emulsiions is difficult and until the mid 70s, Sulfur + Gold sensitization was almost impossible. So, to maximize speed and contrast this way, you have to do a lot of experimentation. And, once sensitized, the emulsions become quite sensitive to keeping.
Glafkides mentions in the text of the Brovira formulas in his book, that keeping is a problem with some of the Brovira family and has left out one step in the making of these that deserves mention. Some of the Cl/Br Agfa formulas use a stabilizing agent to prevent fog and loss of contrast during aging. That too is another grave omission on the part of that table.