How to use benzotriazole?

[TattyJJ]

Google seems to be giving me varied results...
I've some expired film with a mild fog i'd like to try it on, along with some old paper that is slightly foggy.

I'm planning to use D76 for the film, but also have ID-11 and Microphen if they would be more suitable, and Multigrade for the paper.

 

[Kevin Caulfield]

It's usually used fairly dilute, like a 1% solution.

 

[Bill Burk]

I've seen lots of advice to take the dry Benzotriazole and dissolve in a small amount of water or other fairly inert solvent.... and then use that as a stock solution to add to film or paper developers.

I personally wouldn't use it on film unless developing aged, already-exposed film. Because if I were using aged film to take new photographs, I would test the film to find its current effective EI and just blast through the fog with additional exposure and develop in D-76 1:1 as usual.....

The negative/positive process allows you to work with fogged negatives with little image degradation.

But printing paper can't stand fog. That would just make your prints gray and muddy. There's where I'd use the Potassium Bromide solution or Benzotriazole to keep highlights open on paper.

 

[bernard_L]

Starting point would be 0.3 g/litre in working strength developer. For paper as Bill Burk wrote. I have a 100cc bottle of 1% solution of Benzotriazole in diethylene glycol. On second thoughts (or next time) I should do it differently:
- use propylene glycol (less toxic)
- make a stronger solution: adding 0.3g of BTAZ in 1 litre of working strength Dektol uses up 3/10 of my solution;

 

[Doremus Scudder]

First, as Bill points out, you don't need BTZ for old film; just overexpose a bit as needed to get the shadows out of the fog and develop as usual. Test to see how much overexposure is needed then go from there.

For old paper, BTZ can work wonders clearing the whites (I use it on fresh paper to restrain development in the highs a bit sometimes too). I'd suggest you mix a 1% solution of BTZ and then use that to add to the print developer. I make mine using water and it lasts forever.

Start with 2-3 ml of your 1% BZT solution per liter of developer. Add more in 2-3 ml/l increments until the fog is acceptable. If you have to add more than 25-30 ml/l of developer, the paper is likely too fogged to save, or at least to get rid of all the fog. You can try printing heavy with a little fog and bleaching back with a ferricyanide bleach if you really want to use the fogged paper.

Best,

Doremus

 

[TattyJJ]

I'll keep that in mind for next time i use that film (i have 7 rolls) though it's too late for the one i have used...

But there is a stark contradiction above with how much to use?

Starting point would be 0.3 g/litre in working strength developer.

Start with 2-3 ml of your 1% BZT solution per liter of developer. Add more in 2-3 ml/l increments until the fog is acceptable.

My maths could be way off here, but that's a ten fold difference between trying 0.3g/L and 0.03g/L in working strength developer to start with?

This is the same issue i had when trying to google how much to use

 

[bernard_L]

@TattyJ: my references can be found in this post (which created an unexpected reaction...):
(there was a url link here which no longer exists)

But it should not take you too long to make your own experiment. Prepare half a dozen or so unexposed strips of the paper subject to fog; label them by writing on the back. 1/2 litre of paper dev in a small tray. Develop (and fix) strips in (1) plain dev; (2) as per recommendation of Doremus Scudder; (3...) for each successive test , add the quantity of 1% solution to double the cumulative amount from previous test. Compare with a strip that has been fixed skipping the developer. What is the first strip that shows a decrease in fog level wrt #1? What is the first strip that looks similar to the fixed (not developed) strip?

Even bettter, come back on this thread and report the results. This being your paper and your developer, nobody but you can determine the right amount.

Caveat: In actual use, the induction time (time for first signs of an image in the dev tray) will be longer with BTAZ; I'd advise to increase total dev time in proportion. And you also might need a little more exposure (maybe, maybe not).

 

[Doremus Scudder]

...My maths could be way off here, but that's a ten fold difference between trying 0.3g/L and 0.03g/L in working strength developer to start with? This is the same issue i had when trying to google how much to use

Let's address this! Your math is not off, there are just different uses and different recommendations for using BTZ. I've seen 30ml of a 1% BTZ solution as a recommendation for fogged paper too, i.e., 10x what I recommended. However, that is really an upper limit and has a really strong effect. I, and others, find it advisable to start small and work up so as to use the minimum restrainer necessary. This keeps exposure and development changes to a minimum. For slightly fogged paper, a very small amount of BTZ will often do the trick just fine. If it doesn't add more until you reach that 30ml/l mark. After that, there's not much point in adding more; the paper is likely too fogged.

I often use BTZ to brighten the whites in an otherwise dull print, i.e., to actually inhibit some development in the highlights, not to clear fog. I use very small amounts, in the neighborhood of 2-10 ml of a 1% solution per liter of developer, often together with sodium carbonate to increase overall activity a bit.

If you suspect your paper is very fogged, you might want to start with a larger amount of BTZ, or make changes in bigger increments, or both.

Best,

Doremus

 

[GregW]

I recommend increasing exposure vs length of development. After you have determined the dilution to beat the fog, use a stop watch to determine time to max black. Take a strip of paper put some developer in a beaker using a film clip put the so that half is in the liquid. flip on lights and time to black. Then calibrate your exposure so that you get what you need in that amount of development. Just my 2 cents. BTW I'd start with a stronger dilution of developer if that is an option.

 

[Gerald C Koch]

Benzotriazole is slightly soluble in water. However the solubility is high enough so that a 1% solution can be easily made. This is fairly standard practice. As stated it is not usually recommended for film. However for paper the idea is to use a little as possible to eliminate the fog. IIRC the use of BZT really became popular when a large quantity of paper became available as WWII surplus.