Quote Originally Posted by robopro View Post
Yes, it is, I know, but I'm afraid if I start trying to get too technical I'm going to show off my ignorance even more than I am now! :-).
Everyone has to start somewhere, so don't be afraid. Exposing ignorance can be embarrasing but you at least learn something and don't do any harm.

I'm a little too busy to try it right now but I've been thinking I may try making a gelatin emulsion. Of course it won't be on the level you guys are doing, but what the heck? I copied 4 recipes off the web and have read about a dozen patents and I think I'm starting to get at least a basic feel for it. Also think I might try using sodium thiosulphate to try and bump the speed up. One patent I read called for adding 6.7 grams of 1% solution to every 2000 grams gelatin and ripening at 50C for an hour. I managed to break that down to 1 small drop for every 40 grams.
One of the recipes I found calls for 2 ripening periods, 1 for 2 hours and 1 for 1.5 hours, so I'm thinking I should add it during the second phase.
What do you guys think?
The real, short answer is that you can't tell from that info. You need to consider a whole procedure to figure out the range of thiosulfate you should use. Even so, it often requires some experimentation to figure out the optimal level. The optimal level can change depending on the gelatin impurity, temperature of precipitation, duration of precipitation, amount of salt used during precipitation (especially at the beginning), and A LOT of factors. Seriously. The detail gets long, but this is because the optimal amount of thiosulfate added for chemical sensitization (digestion) depends strongly on the crystal structure (cube, octahedral, tabular form of octahedral, or tabular form of cube, etc.) and also strongly on the grain size. The detail is always a long story when it comes to the topic of emulsion sensitization, but it doesn't require a lot of work to make a slow emulsion (ASA single digit). (If you want to make ASA three digits emulsion, you better learn all the latest tricks in this.) More of a problem for you is that emulsions that are sensitized with sulfur only typically produce strong highlight contrast and poor shadow details. (Look at photographs taken before gold technique was used and you'll know what I mean. If you make your own emulsions and try you'll actually experience this.) For camera negative emulsions, it is best to use gold plus sulfur technique, which is quite a bit more involved, but will give MUCH better shadow rendition. For faster emulsions, you need reduction, gold plus sulfur technique, which is CONSIDERABLY more involved...)

If you begin with print emulsion, your life will be a lot easier, because you can make quite practical emulsion of good tonality and speed with sulfur only sensitization.