Some back information on emulsion making
In order to try and clarify some points here, I will give some "history" of emulsion making.
Period before 1945:
Emulsion making in the public press was empirical and lots of information was left out of published formulas. Each "researcher" wanted to make a major coup in the field.
At this time, there was only active gelatin for making, and it came in 3 or more forms. Generally, these were ranked as soft, medium and hard. This referred to contrast or sometimes speed. Each gelatin company manufactured a different "trio" of these and each "researcher" preferred a different set. Very often, the type of gelatin was omitted in a formula for secrecy or to allow other dabblers some leeway in what to use. Also omitted were addition times and temperatures, two critical issues that were deep dark secrets.
Commercial emulsions were kept secret. Nothing was published about them.
However, some give a break point in the time line when Sheppard of EK published his monumental work on Sulfur sensitization. Since formulas and the new inactive gelatins were not readily available, the break (in my mind) came in about 1945.
This early period was characterized by a lot of public "art" or "beauty" emulsions with no fully published formulas and which used some pretty exotic methods or chemicals to give them their "glow". These quoted comments often came from the empirical workers trying to attract adherents to their school of photography.
Period: 1945 to about 1970
During this time, few empirical workers survived. This was the age of big photo companies. But, OTOH, since the Agfa formulas had become public property, almost everyone but Kodak used them. This includes EFKE, ORWO, FUJI and a host of others. It was characterized by extreme secrecy at EK with a "Silver Curtain" over all emulsion work. So, there were roughly 4 families of products "Agfa type", Kodak, Dupont and Ilford. Gradually, Fuji and Konica began to diverge with some excellent original work leaving many others with the "Agfa" type formulas.
Agfa formulas, as published gave addition times and temperatures along with final conductivity after wash and gelatin time. They were obfuscated by either poor translation or outright misleading statements by the German scientists and engineers and thus you see many errors where they are reproduced.
This was the big era of Cadmium, Lead and Mercury.
Period: About 1970 to present
This era was still shrouded in secrecy, but the big 3 (Kodak, Ilford and Fuji) had moved far from any Agfa type formulations (Not that I could every find any use of the agfa formulas at EK). All heavy metals were removed and either the products died or the metals were replaced by special organic chemicals.
This era was marked by the use of computerized makes and very complex and long precipitations. I have seen formulas that took up to 3 hours. Oh, I did one AAMOF!
This was a 9% Iodide emulsion for very high speed.
Now - MY GOAL.
1. To show the early method along with its faults and false trails. Some claim that there are no false trails, but there are! Believe me.
2. To use the middle period with some EK nohow to get ISO 25 - 200 ortho and pan emulsions that are simple enough to make in a home darkroom. With my help, some of my students are nearing the mid range. But, others claim that I am wrong in my approach and am making it too hard. Well, too hard is in the eye of the beholder or what one wants to achieve. I hear no complaints (other than the cost of AgNO3) from those getting ISO 100 emulsions.
3. To document the recent trends. I do not urge or suggest anyone get into this unless they are really interested and dedicated. I've been successful so far. No takers. BUT, I have a PM mail box stuffed with messages from those with questions about items 2 and 3 here. So...
Anyhow, the varying opinions on what is "right", "proper" or "wrong" in this entire post have lead to many hours of argument on-line and many pages of deleted posts.
I offer that Ian is right. There are no wrong or right answers, but with nearly 40 years doing this stuff, you might conceded that I am right more often than wrong. Now, this may be the wrong way to end such a post. Maybe I should never have made it at all. But, for those interested, the book gives several more pages of this stuff with diagrams and etc.
I am becoming more and more discouraged about this all. Of what use is is if just about every post I make on my own expert field of endeavor is questioned!
Best wishes to all.
PE
, I don't think he seems at all sad and confused.
