Quick note on a typo in post #8. It's 1966, not 1996.
It's an excellent article. The full citation is: T.T. Hill, "Laboratory Scale Photographic Emulsion Technique," J. Chem. Educ., 43, 492 (September 1966).
The SPSE Handbook that Jason mentions is invaluable. Its full name is:
SPSE Handbook of Photographic Science and Engineering. Edited by Woodlief Thomas, Jr. (a.k.a. "Woody" Thomas), 1973.
(also: "EK" is insider speak for Eastman Kodak)
Chemistry math refresher
Since it's been (ahem) 42 years since high school chemistry, I need some help with the calculations to get the whole milligrams per mole thing straight in my head. Silver nitrate AgNO3 has one silver (107.9) one nitrogen (14) and three oxygen (16x3=48) for a mole weight of 169.9, of which 63.50% is silver
Sodium Thiosulfate Na2S2O3 has a molar weight of 248, of which 25% is sulfur.
Iím using about 5 grams of AgNO3, and this is where I get stuck and my memory fails me.
5 grams of silver nitrate has 3.175g of actual silver.
1 gram of sodium thiosulfate (dissolved in 100ml of water) has 25mg in the bottle.
Where, mathematically, do I go next?
Thanks in advance,
It is 5/169.9 to give moles of silver. Once you have that, you use 248 x 25% to get the quantity of sulfur and use that at X mg / mole for the emulsions in my book. Of course I have used 100 mg of Sodium Thiosulfate Pentahydrate per mole which is not exactly 100 mg/mole. It is less than that.
I think Joe's question is what I was originally trying to get at a few weeks ago but he's asked it much more clearly.
Joe, are you joining the emulsion making club or are you already a member? Are you making PE's ISO 40 SRAD? Please let us know how it works out for you.
I tried to be clever and make a variation of the ISO 40 last week and completely killed it. But I believe I know what I did as in I added a stabilizer early in the digestion which I later found out totally arrests the process. It is very insensitive and fogged. Shortly, I'll have to try again and follow the directions correctly without trying to be clever. (Note: the stabilizer was not the supposedly clever part.)
PE, I had a question for you: does the Ammonium Thiocyanate in Steigman's Gold Sensitizer (as given by Denise and TT Hill) contribute any sulfur to the sensitizing process? As I understand from my reading, the Am Thio combines with the Gold Chloride to form AuSCN, but I haven't been able to clearly discern if the SCN contributes any sulfur or not. Originally I thought it did but now I am not so sure.
My chemistry was only 35 years ago and you remember more than I did, Joe.
Thanks Ron for the quick reply. It will be nice to see you again in March.
Originally Posted by kb3lms
As to my memory, well It's not what it was, but I find it's still better than average.
Jason, I took Ron's emulsion making 101 in January 2011 and have been rummaging around ever since. I had some trouble in Late 2011 and early 2012 (divorce and two eye operations) and dropped out of sight for awhile but I'm back, healthier and happier than ever. Since I tend to photograph in the warmer months then cocoon in the darkroom in the colder. . . .
As to the emulsion, I'm starting from the basics again (AZO) and it's coming back to me quickly, but reading this thread I was confused (natural state) and thought I'd ask. Then on to Ron's book before the workshop at GEH.
All the best,
The Steigman's solution does contribute Sulfur, so watch out!! You treat this just like Hypo with an emulsion.
Do not use Sulfur or Gold with the Azo emulsion.
OK, Ron, but why?
Originally Posted by Photo Engineer
I imagine Ron will come back with more details, but I can give you the short answer: There's no need. It's a waste of time and money. In addition, it just doesn't work as well with a Cl emulsion.
Azo is a very slow contact printing Cl emulsion. Its claim to fame is that it's beautifully "clean", i.e. the whites are white, or at least close to the color of the paper. The emulsion doesn't need speed, and speed is the only reason to add gold and sulfur. Gold sensitization almost always contributes a tiny bit of base fog, which can actually be a fine thing with film, but is disasterous with paper.
A Br emulsion is inherently faster that a Cl emulsion, even without sensitization. With a BrI emulsion, one whose reason-for-being is speed, gold can be worth the extra effort and money involved.
Chloride emulsions do not like S or Au! This is a problem of chemistry. So AgBr + S + Au is good but AgCl + S + Au is bad. In fact, unless you have a lot of background, AgCl + S is bad too!