Anti-fogging chemicals

Which compound is the best at reducing base fog?

...and (if you don't mind the semi hijack), in what amount should they be added to a liter of print developer? How about to a liter of film developer?

...and, correct me if I am wrong, but is it not just "fog", not "base fog"? The term of which the OP is thinking is "base plus fog", meaning the density of the film base plus the density of the fog. TMK, the base itself cannot be fogged, only the emulsion.

I don't mind. I've wondering what amount should be added as well. As to the term, I just checked it and it is shown both ways by various sources.

I'm fond of benzotriazole myself.

The 2% Benzotriazole solution

Darkroom317 said:

Which compound is the best at reducing base fog?

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I haven't printed FB for a couple of years (shame!!), but a friend gave me four boxes of expired Brilliant-IV FB paper. I ran a control test with his paper, as well a some badly base-fogged AGFA Multicontrast FB, and some fresh Foma FB paper.

AFAIR, I added 100ml of a 2% benzotriazole solution per litre, at working strength, of Arista Aristadol Powder Paper Developer. I found that that amount of the 2% benzotriazole solution seemed to do the trick. I started with about 10ml per litre, and gradually worked my way up.

The addition of the 2% benzotriazole solution not only cleaned up the whites and highlights, but it seemed to increase the contrast slightly and it caused te image tone to "cool down" a bit.

I will check my notes and get back to you on this. If you haven't heard from me by Monday, May 10th, feel free to PM me until I produce the data!

Yes, Terrence is right. Start low and work up. Use a more concentrated solution than 2% though. I suggst 5% just so you don't dilute your developer too much. Sodium Bromide at about 1 g/l is a good antifoggant for papers as well.

There is also PMT, or Phenyl Mercapto Tetrazole. Used at 1 mg - 10 mg/l it is a good antifoggant. It is sold by the Formulary.

All organic antifoggants tend to cool down image tone.

PE

Darkroom317 said:

Which compound is the best at reducing base fog?

Click to expand...

Studying some formulas, I see potassium bromide being used between 2-5 g/l as a restrainer.

Does no one consider restrainers as anti-fogants as well?
PE mentions Na Br. More common to me is K Br. I add 10% potassium bromide, up to as much as 30mL/L, which is a lot. It warms the image tone, but also restrains development action.

I find that I can deal with a lightly fogged paper by adding bromide, and exposing longer to compensate for the restained development.

I keep the developer warm, say 22-24C, by periodically pouring some into a jug and popping it in the microwave for a reheat, and then adding the warm stuff as the contents of the tray satrt to cool too much.

With the warm developer, the image comes up quite quickly, so 1.5 minutes in the dev is usually enough. By going with the short developmet i find that the fog is not as pronounced as if developing to 2:00 or 3:00.

Anti-foggants have a marked effect on image colour with warm tone papers, as Ron (PE) says organic anti-foggants cool tones while Bromide does the opposite giving warmer tones.

Ian

NaBr and KBr are exactly equivalent in effect if you compensate for the tiny molecular weight difference between K and Na. They give the same effect which is based solely on Br.

Any antifoggant is essentially a restrainer.

PE

Actual percentage of the benzatriazole solution...

Photo Engineer said:

Yes, Terrence is right. Start low and work up. Use a more concentrated solution than 2% though. I suggst 5% just so you don't dilute your developer too much. Sodium Bromide at about 1 g/l is a good antifoggant for papers as well.

Click to expand...

My memory may be playing tricks on me, and I won't know until I actually retrieve my notes this evening. The benzatriazole solution may, in fact, actually have been a 10% solution.

Permit me to shift off topic: PE, could a benzatriazole solution be used as a supplement to, or in place of, potassium bromide, in a negative developer, to compensate for excessive fog caused when the development time is extended?

I have used D-23, with a time of 20 minutes @ 100°F, when developing negatives made under streetlights, during a candlelight vigil. The negatives look fogged (which I suppose, they are), and probably could have done with a 50% reduction in development time. But would/could a benzatriazole solution have been added to D-23 to hold the fog level down?

Antifoggants work for film or paper but the levels are quite different and must be determined by trial and error.

PE