View Full Version : Pyro Staining and Grain Masking

Kirk Keyes
18-Jun-2004, 11:04
Richard Knoppow wrote in the ViewCamera.com posting recently, "The idea that the stain image masks grain is probably not true although widely believed."

Sandy King wrote in another thread here, "[...] in my opinion he is just dead wrong on this subject. Anyone who has experimented with pyrogallol and pyrocatechin developers in non-staining formulas knows for fact certain that the appearance of grain is much less in staining developers than when these reducers are used in non-staining formulas."

We all know that some of the optical density of a stained negative is from the stain and some of the optical density is from grain. Perhaps this lack of the appearant graininess of stained negatives is not because of some sort of "stain image masking" the grain, but simply that there is less actual grain in a stained negative than a nonstained one. Since there is less grain producing the density, the image is less grainy appearing.

The staining developer may also produce silver grains that are actually smaller, since we don't have to develope the silver grains as much to generate optical density since the stain is silmutaneously producing it. This could produce grains that are actually smaller which would help the illusion that the grain is being "masked".

Nothing magical, just simple optics and chemistry.

Any comments?

Jorge Gasteazoro
18-Jun-2004, 11:30
If your hypothesis is true, wouldn`t we have more grain? as the grains are further apart from each other, since there are not as many.

Just a thought, frankly I dont care as long as I dont see grain I am happy....Besides I am still tired from the last pyro debate, I think I am staying out of this one...:-))

Jay DeFehr
18-Jun-2004, 13:48
Kirk, I think you make some valid points that contribute to the reduced graininess of pyro negatives in addition to the grain masking, which is also "just simple optics and chemistry".

19-Jun-2004, 17:04
I agree that Kirk makes a good point. Since grain is most apparent in the high densities, and this is where there is the greatest amount of stain, it is logical to assume that one of the main causes, if not the only cause, for reduced grain in pyro stained negatives is the fact that there is less silver density in the highlights.

Perhaps the difference of opinion between Knoppow and me is due to a difference in udnerstanding of the meaning of the word. My understanding of the use of the term is simply that it describes a final result, i.e. negatives developed in pyro staining developers have less visible grain than negatives developed in non-staining pyro developers, when each is developed to the same CI. I don't believe anyone who has compared staining pyro develoeprs with non-staining pyro developers would question this fact.

19-Jun-2004, 19:44

What's an example of a 'non-staining pyro developer'? I thought that any developer that used pyro as a reducer would stain.


19-Jun-2004, 20:24

I am away from home at this time and can not give you an exact formula but if you add enough sulphite to virtually any Pyro formula, including ABC Pyro, you can make it non-staining, or at least dramatically reduce the amount of stain.

Jorge Gasteazoro
20-Jun-2004, 00:46
Jim, when I was playing with ABC, I added phenidone to it, to try and get more speed out of the film. Even though I increased the dilution to 15, the negatives were bullet proof and had no stain. I think in the darkroom cookbook there are a few formulas for non staining pyro developers. If you have the book look them up, if not, let me know and I will look them up, I know I have a book that has them.

Jay DeFehr
20-Jun-2004, 14:41
Jim, I know you're getting along quite well with your current developer, and I suspect your question was borne out of curiosity more than investigation, but I also have a few non-staining formulae if you want them.