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Paul Verizzo, I agree on most of what you are saying. I have a question @[5] though. If the amount of developer in the emulsion is the limiting factor and develops until exhaustion (in the highlights) how can temperature lead to more contrast? as far as I understand higher temperature will only lead to the exhaustion faster? Or am I missing something?
Kind regards
Paul: What's the formula as specified by Otha C. Spencer? Thanks.
Hello Paul, I was looking at your formula for the Otha C. Spencer formula.
I'm trying to figure out what your abbreviations stand for. Did I get this correct?
Bath A
Metol, 6.5 g
SS, 32.5 g (Sodium Suplhite)
HQ, 6.5 g (Hydroquinone)
Pot. Bromide, 3 g (Potasium Bromide)
Water to make 1 Qt.
Bath B
10 g Kodalk (sodium metaborate)
Water to make 1 liter
or
?? g Borax
water to make 1 liter.
Thanks
Hydroquinone has about twice the increase in performance with temperature as any other common developing agent. Without actually finding my reference, it's something like most developers have a 1.2 coefficient. HQ is 2.5. HQ, of course, is well known as a contrast developer because it is not too effective in the shadows. What it can get hold of, though, it develops well. Sort of the opposite of pure Phenidone.
The ratios I mentioned come froma Haist, I think. Regardless, they are the ratios that give maximum silver reduction. But if the temperature changes from the design temperature (usually 20 C., of course), the developer activity changes for each developer. Of course, it ALL works faster, too.
I hope that helps.
Yeah, you passed the APUG I.Q. test!Spencer actually says 91 grams of sodium carbonate for Bath B! That's a pH of over 11; I made some. 10 grams of sodium metaborate gives a long lived bath of pH 10.5. As you might know, the difference between 10.5 and 11+ (my pH paper wouldn't measure exactly) is substantial. However, in reducing the silver, it's not so much. pH 10.5 via 5 gms of carbonate per liter worked great for me.
So what you are saying is that not only the developers activity but also capacity is increased?? or is it a matter of the amount of developer precent in the emulsion?
Kind regards
Thanks, next week I'm going to try walking AND chewing gum at the SAME time. I'm just starting out mixing my own developers, so it's all a little new to me. GOt to pick up a copy of the Darkroom Cookbook.
Paul, are there times listed with Spencer's 2-bath?
Some people have reported that they see drag marks if they do stand developing with Paterson type reels rather than stainless steel ones. I just used Diafine for a roll of Tri-X and did not have a problem. One problem you may be facing is that 3 minutes is a very short stay in Part A. I use Amaloco AM-74 at 1:15 becaus ethe times at 1:7 are too short for my liking. This is also why many people use HC-110 with higher dilutions than B. With a stainless steel reel and adequate agitation this problem should not show up.
...you are using "capacity" to mean "able to develop more latent silver."
Gelatin swells more with increasing temperature, thus allowing more developer or whatever into the emulsion. So, in that sense, probably. If using a two bath at an elevated temperature I would expect somewhat more development. I've never run tests, just my theory.
Regardless, it will be the greatly increased activity of HQ with rising temperatures that will cause much greater contrast. This is true for any developer with HQ, single bath or two bath.
Do you have any references to back up that theory or can any one else here agree?
I my textbook the developer in the emulsion have a limited capacity it may be greater than the amount of silver requires but nevertheless its limited. If the capacity is much greater than need I must agree with you regarding the higher contrast if not then I disagree.
If amount of developer is the limiting factor you will never get higher contrast by increasing the temperature. On the contrary the highlights will be exhausted very fast and the midtones and basefog will be increased resulting in lower contrast. But then again there must be a safety factor built into the formulary assuring the right amount of development somehow.
Im obviously not an expert on this but Im puzlled
Kind regards
I would think this is one developer that would do well to avoid gentle agitation. You might try a sacrificial roll in it and give it good agitation, especially at the start, so the chemicals can get distributed evenly as it diffuses into the emulsion.
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