Benzotriazole anti-fog
 

Benzotriazole can be used in the print developer as an anti-fog additive.
Used when you have old out of date bromide paper to use up.
The internet has a few pieces of information regarding the percentage of the stock solution to be made up, and the amount to mix into the developer.
Trouble is, no one seems to agree with each other as to the quantities to use etc..
Has anyone had any personal experience of using this chemical, and what stock solution to mix, and how much to use in the developer ?
Cheers.

My experience with 1950's and 60's Ilford and Kodak Bromide papers is loss of speed and maybe a grade contrast but no fog.

I had many hundreds of sheets of 50's and 60's Bromide paper, and tested it all before giving it to people who ran workshops.

Fogging from poor storage is another issue. doesn't need to be old at all in this case.

I have a lot of Benzotriazole. powder and in Solution, in over 50 years of darkroom printing I've never used it unless a developer formula includes it.

Ian

I too have some in stock, but to date have never had to use it as you suggest.

I bought a small quantity as I am now making my own brews from individual chemicals, and as stated, some formulas include it.

From what I've read, one uses a 0.1% solution, (which would be 1 gramme in one litre of VERY hot water at 125F / 52C or higher, as it won't dissolve in lower temperatures) and then using up to 5ml in your diluted developer, starting at 1ml, until you (hopefully) solve the fogging problem. I say this as I don't think that it is a cure all, in all cases.

Hopefully Pentax Pete will see this question, as he has done a lot of videos about this type of thing.

Terry S

I recall from Photrio, I think, that stronger solutions of benzo will work up to a certain level of age fogging but not beyond that. I'd imagine that anything up to light grey might be curable but once you get beyond that then while you will clear the borders back to a light grey or possibly very light grey then you may have to live with slightly grey borders which as long as the picture comes out OK may be fine.

Depending on the photo a light grey border might look OK

Mike

I have used up to 15ml of a 1% solution of benzo. Added to my print developer. Adding more benzo than that amount will do nothing for paper that is heavily fogged by ageing. Compare a print made on new paper next to successive prints made on your fogged paper adding 5ml, 10ml and then 15ml of benzo. 1% solution. Or jump right in with 15 ml benzo. Per. Litre of print dev. Compare the whites to the whites on your fresh paper print any degree of grey on the old paper will be easy to see.

I have used up to 15ml of a 1% solution of benzo. Per 1ltr of print dev. added to my print developer. Adding more benzo than that amount will do nothing for paper that is heavily fogged by ageing. Compare a print made on new paper next to successive prints made on your fogged paper, adding 5ml, 10ml and then 15ml of benzo. 1% solution. Or jump right in with 15 ml benzo. Per. Litre of print dev. Compare the whites to the whites on your new paper print, any degree of grey on the old paper will be easy to see.

A few variations of using benzotriazole
 

Well, having read over the years many times to use a @ 0.1% solution, I took to my books for a definitive answer.

So prepare to be educated / even more confused than ever... :)

First, the Darkroom Cookbook, which says:

'Mix a 0.2% solution (2 grammes in 1 litre water at 125F / 52C or higher). Add 15.0ml of this solution to every litre of (working strength) developer. If 15.0ml does not do the trick, keep adding 15.0ml at a time... until you get a clear paper without a fog. A little experimentation will be required.'

Note that it doesn't give a maximum amount that can be added, but general reading says that adding too much will introduce even more fog.

Secondly Ansel Adams, The Print states that he uses a '1.0% solution, adding 25cc to stock developer solution.' It says that 50cc produces a noticeable blue colour shift of the paper and 100cc reduces paper speed by about 2/3 of a f-stop.

Thirdly and last is from Tim Rudman's Master Printing Course book:

'Benzotriazole 1%. 5ml in 1 litre of working developer. Expose to the shortest recommended development time and then experiment to ensure maximum blacks.'

Also recommended in his book and else where, is the use of potassium bromide 10%; using 10ml in 1 litre of working solution.

Note that bromide gives a warmer image compared to a cooler one with benzotriazole.

Hopefully this will all be of help and the bottom line seems to be to experiment a bit. :)

Terry S

Thanks for the summary of instructions, Terry. Just a pity perhaps that that the wording in the Darkroom Cookbook gives me the impression that clear paper will always result, eventually, which is unlikely to be the case with paper fogged beyond a certain level.

Mike