gainer said:I have been testing the substitution of hydroquinone for catechol in Pyrocat MC. I'm amazed. It is water white clear, and has remained so for several days. It immediately colors up when the carbonate is added, and the stain it produces is not so much different from that of catechol to my eye, but it may be quite different to alternate printing processes. It is a very vigorous developer, about the same as Pyrocat MC, and tanning is quite evident. .
Ryuji said:DS-10 is a very good fine grain developer. Usually, fine grain developers cost in terms of loss of speed, sharpness, or both. However, DS-10 affects neither speed nor sharpness, so in this sense, I use DS-10 as my general purpose film developer. One thing to remember is that it shouldn't be used for Pan F Plus, APX 100 and perhaps some other slow films using non tabular grain technology. The result is obvious loss of speed, contrast and density. (It's very obvious so a clip test should tell you.)
I've made several improvements to DS-10, but they are meant to improve image quality with 100+ speed films, and to improve keeping properties. As fixing the above incompatibility issue costs in terms of image quality, I am not sure of incorporating such improvements in the future. (However, I have a new developer that works superbly with those slow conventional films, as well as fast films, with excellent push property, so they are nicely complementary.)
Yes. I figured since the molecular weights are the same, I should use the same amounts.sanking said:Did you substitute the hydroquinone at the same amount as pyrocatechin?
Sandy
gainer said:Yes. I figured since the molecular weights are the same, I should use the same amounts.
From what I have read in The Theory----, the color of the dye image is the same as the color of oxidized developing agent. This conclusion was reached by those who had the means and knowledge to do a chemical analysis of both. I don't know how to make a proper comparison by eye. Perhaps there is some way to equalize the effects of concentration, etc. If I leave a cup of most any developer sitting open long enough, I can't see through it.
For some, the color is not as important as it is for others as long as it looks like density to graded paper. I would not make any claims for hydroquinone as a staining developer for any of what we call alternate printing processes. All I can say is that is can stain, and might be a way to do at least a preliminary test of a developer formula without wasting the more expensive catechol. It has some of the other properties of catechol that seem to affect sharpness, such as tanning the gelatin in proportion to the image. I'm thinking of differential refraction at edges due to differential hardening.
Thanks Richard,eclarke said:Hi,
Which developer is this one? I also expose some PL25 and this sounds interesting to me..Thanks..Evan
gainer said:Salicylic acid is a fungicide used in patent medicines such as Scalpicin and one of Dr. Scholl's remedies for athlete's foot. Scalpicin is 3 %. I don't know about the other. It would be more expensive, I'm sure, but maybe worth it. You could also look at the other ingredients in Scalpicin to find what solvents are used. IIRC, propylene glycol is one of them.
Pre-dissolving the salicylic acid in alcohol or a glycol may not help. This technique works with chemicals like phenidone that are difficultly soluble in water but eventually dissolve ie, they are at a concentration below their maximum solubility. Adding an alcohol solution of salicylic acid to try to get 4 g/l to into solution will only result in 2 g/l actually dissolving and the the other 2 grams precipitating out. The maximum solubility of salicylic acid is only about 2g/l. This would prevent making DS-10 in a 5X concentrate.Jordan said:Can you pre-dissolve your salicylic acid in some alcohol?
That makes sense, I will just grin,bear it, and wait for it to dissolve. The results are great with Tmax 100..Thanks..EvanGerald Koch said:Pre-dissolving the salicylic acid in alcohol or a glycol may not help. This technique works with chemicals like phenidone that are difficultly soluble in water but eventually dissolve ie, they are at a concentration below their maximum solubility. Adding an alcohol solution of salicylic acid to try to get 4 g/l to into solution will only result in 2 g/l actually dissolving and the the other 2 grams precipitating out. The maximum solubility of salicylic acid is only about 2g/l. This would prevent making DS-10 in a 5X concentrate.
True enough, but if the object was to make it quicker to get 2 g/l or what ever the recipe called for, keeping the salicylic acid in some kind of separate solution would do that. The 3 % solution of Scalpicin has 30 grams per liter in propylrne glycol, some other alcohol and water, so one would only use a little of that to make a liter of working solution with 2 g/l or less.Gerald Koch said:Pre-dissolving the salicylic acid in alcohol or a glycol may not help. This technique works with chemicals like phenidone that are difficultly soluble in water but eventually dissolve ie, they are at a concentration below their maximum solubility. Adding an alcohol solution of salicylic acid to try to get 4 g/l to into solution will only result in 2 g/l actually dissolving and the the other 2 grams precipitating out. The maximum solubility of salicylic acid is only about 2g/l. This would prevent making DS-10 in a 5X concentrate.
Thanks Gerald,Gerald Koch said:Rather than a glycol solution it might be easier to keep a stock solution of TEA and salicylic acid on hand. This avoids adding an additional component to the mix. Salicylic acid should be easily soluble in such a basic solution.
Gerald Koch said:To test that it works, I would mix up 100 ml of TEA and 10 g of salicylic acid to make a 10% solution. I would add the acid to the TEA. It may dissolve without having to heat the mixture since a salt is formed which is triethanolamine salicylate. If it doesn't dissolve then I would gently warm the mixture with stirring until it does. You would then use 10 ml of the mixture for each liter of DS-10 made. If you find the mixture too viscous to measure easily then add an equal volume of water and use 20 ml of the mix for each liter.
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