Denise Ross has just posted her website that is devoted to making photographic emulsions. She has examples and practical info on making papers, negs, gums, and more on the site.
It's called The Light Farm - check it out at http://www.thelightfarm.com/
I have made a batch of Azo type emulsion that showed pepper grain on one batch of Baryta paper, none on another and none on Strathmore, so I can believe that old story has some credibility. I believe that several people have seen some of my paper which Alex Hawley used for printing. I doubt if there is any pepper grain. Maybe they would care to comment.
PE
Ron:Photo flo 200 and 600 differ in that 200 is more dilute and uses propylene glycol as an additive while 600 contains ethylene glycol (at least this is what the MSDS and my bottles say). I use the former as it is less toxic, but they are basically the same except you use a different amounts of either as they differ in concentration. They are nonionic surfactants. The active surfactant in the Photo Flo series is what we used at Kodak for making our coatings. You can substitute Triton X 100, which is essentially the same thing.
PE
"Coating defects on papers can be caused by inadequate mixing when adding hardener, or can be caused by ineffective surfactant. The surfactant used in Photoflo (octylphenol ethoxylate) is not very effective for coating purpose, unless you coat slowly, or make multiple strokes (like when using brush). If you have no access to a better surfactant, try to wet the coating surface with plain dilute surfactant, immediately before coating the emulsion."
You are probably referring to Photo-Flo 200, the form of surfactant most commonly used in the home darkroom as the final step in film developing.
This is actually a factor related to gelatin, agitation and the kettle shape/size. If agitation is very vigorous and more dilute silver jet is added very slowly, pepper is less likely to occur, but then if you use a gelatin that has stronger peptizing power, pepper fog is far less problematic under the same mixing condition. So everything is related. One another point is the shape of the mixing vessel, especially if your batch size is large. Regular cylindrical beakers are not very good because there is a region of ineffectively agitated area near the bottom edge. Something like cooking bowl shape is best, although ones made from opaque nonmetal materials are hard to find (it has to be nonconductive material to be compatible with magnetic stirrer you use).re: pepper fog: It's been my experience that pepper is primarily a problem of uneven silver addition during the precipitation step.
Kirk also requested some of the emulsion formulae, and I'm putting together a little formula collection when I find spare time. He is mostly interested in 100-speed negative emulsion. Do you have a request for a particular type of emulsion?
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