PB vs BZ

David Lyga · Jul 25, 2020

Do any of you FAVOR potassium bromide over benzotriazole, and why?

I always use the benzotriazole and rarely use the other. One needs to use FAR less BZ than PB and I want to know if there is something that I am missing with eliminating the bromide from my inventory.

I find that the combination of an enhanced level of hydroquinone (in combination with a small amount of benzotriazole) in a formula does wonders for reducing age fog. The hydroquinone increases the desperately needed contrast in old materials and the benzotriazole reduces the fog which is prone to emanate from this forced development. The 'cost' is a far slower film speed (in order for exposure density to be able to navigate well above the threshold fog level). I feel that that is a small price to pay for results.

In essence, are there any advantages which potassium bromide has over benzotriazole? I find none. - David Lyga

Donald Qualls · Jul 25, 2020

Potassium bromide, in my experience, makes a much better "integrated" restrainer -- that is, written into the developer formula, mixed along with the developing agent(s), preservative, accelerator, grain modifiers. Benzotriazole is almost never called out to go in the original developer mix, probably because it's so much more effective. Too effective.

Sure, for shooting forty-fifty year old film, BZ does the job much better than KBr -- but that is (or ought to be) an unusual situation. Most developers are designed for the situation of most photographers -- shooting fresh (or at least recently expired) film and processing it more or less promptly.

David Lyga · Jul 25, 2020

Thank you, but I am most concerned with heavy fog here. However, Donald, even taking your theory as being intact, I have an issue with your claiming 'too effective' as a reason for preferring the bromide. Why? Because one mere gram of BZ can be mixed into, say (as I do), 400 mL of water. THEN a tiny bit of BZ, in the easy to measure diluted solution, can be accurately measured into the developer solution. - David Lyga

grainyvision · Jul 26, 2020

Benzotriazole primarily works by reducing the speed of an emulsion. You can test this yourself by adding a bit of BZT to a paper developer and making a few test sheets. Pretty much only highlights will have a density difference. Bromide works quite differently. Bromide slows down overall development, including in the most dense areas. BZT I'd say is the best agent to use (or other antifoggants like PMT) for decreasing fog, IFF also over exposing the film. For general developer formulation though, the typical speed decrease of BZT is non-ideal, and bromide has an effect on the contrast levels of a developer which is often wanted for various reasons. Bromide also can decrease emulsion speed, but only by making low density development too slow (you'd get it back by extending development, but likely with clipped high density areas). BZT will make fog incapable of development, at least until you get to the amount of development extension that would induce developer fog

grain elevator · Jul 26, 2020

I've read somewhere that seemed trustworthy to me at the time that bromide doesn't work well with Phenidone and so for these developers benzotriazole is the only way. I think it must have come from P. Gainer or R. Suzuki, as I was researching ascorbate developers.

David Lyga · Jul 26, 2020

This 1979 thesis from Rochester Institute of Technology might be of interest:

https://scholarworks.rit.edu/cgi/viewcontent.cgi?article=6080&context=theses

Donald Qualls · Jul 26, 2020

Also, you might want to read this article on cold development with BZT as a means of salvaging old, badly fogged film for exposure in the present.

Lachlan Young · Jul 26, 2020

grain elevator said:
I've read somewhere that seemed trustworthy to me at the time that bromide doesn't work well with Phenidone and so for these developers benzotriazole is the only way. I think it must have come from P. Gainer or R. Suzuki, as I was researching ascorbate developers.

Given that neither of those individuals were actual photo chemists/ engineers and that Ilford quite happily used KBr on its own (ID-68 and ID-78 for starters) or with BZT in several disclosed PQ developers, I'll go with Ilford's research in preference.

NB23 · Jul 26, 2020

I’ve finished printing a huge batch of ilford mgIII badly fogged.

A lot of benzotriazole helped me reach the point of somewhat acceptable results while no amount of potassium bromide could work.

I’m no chemist and I’m not answering your question, but I confirm that benzo works drastically.

NB23 · Jul 26, 2020

earlz said:
Benzotriazole primarily works by reducing the speed of an emulsion. You can test this yourself by adding a bit of BZT to a paper developer and making a few test sheets. Pretty much only highlights will have a density difference. Bromide works quite differently. Bromide slows down overall development, including in the most dense areas. BZT I'd say is the best agent to use (or other antifoggants like PMT) for decreasing fog, IFF also over exposing the film. For general developer formulation though, the typical speed decrease of BZT is non-ideal, and bromide has an effect on the contrast levels of a developer which is often wanted for various reasons. Bromide also can decrease emulsion speed, but only by making low density development too slow (you'd get it back by extending development, but likely with clipped high density areas). BZT will make fog incapable of development, at least until you get to the amount of development extension that would induce developer fog

Great answer.
So, both are drastically different and do not serve the same purpose. It is an error to think that they could be interchangeable.

David Lyga · Jul 26, 2020

NB23 said:
I’ve finished printing a huge batch of ilford mgIII badly fogged.

A lot of benzotriazole helped me reach the point of somewhat acceptable results while no amount of potassium bromide could work.

I’m no chemist and I’m not answering your question, but I confirm that benzo works drastically.

To make this even more effective: Increase the hydroquinone in relation to the metol.

The union of hydroquonine and benzotriazole is a marriage made in heaven, but you need a little of the priest to officiate. That tiny, little priest is Father Metol, or, vicariously, Father Elon. - David Lyga

NB23 · Jul 26, 2020

David Lyga said:
To make this even more effective increase the hydroquinone in relation to the metol.

Hydroquonine and benzotriazole are a marriage made in heaven, but you need a little of the priest to officiate. That tiny, little priest is Father Metol, or, vicariously, Father Elon. - David Lyga

Thanks for the good info!

But to be honest, I hope to never have to deal with bad papers again!

Exposing each of the 1000 sheets I had for a
Whole minute to 1:30 (instead of 15-30 seconds), and then developing for 3-4 minutes, instead of the usual 1 minute, really got to me in the end.
And then brown toning just to get acceptable results... it was hard work.

let’s roughly calculate the lost time for, in the end, still subpar results: I process 4 sheets together in each bath.
So 1000/4=250.
250 x 3 minutes extra in the developer= 750 minutes.
Exposing each sheet 1 minute extra = 1000 minutes.
Brown toning for 15 minutes, 50 prints at a time. That’s 20 Sessions of 15 minutes = 300 minutes.

So in conclusion; in order to save roughly 350$ of papers I have lost 2050 minutes (34 hours) working on bad papers.

Yes! I’ve worked 34 hours extra for subpar results, all in order to save 350$. I’ve been quite stupid, if I think of it.

And then, fresh paper is so wonderful!

MattKing · Jul 26, 2020

Did anyone else look at the thread title and wonder what David was going to post about peanut butter?

DREW WILEY · Jul 26, 2020

I use both, sometimes together, but mostly for different developers. Bz is about 10 times as strong as KBr. It can enhance the coldness of a print, but if you are gold-toning, it's counterintuitive, and you actually want a finer warmer grain and KBr, which then inverts to cold upon toning. There are of course all kinds of exceptions, depending. I also find Bz to be an excellent film restrainer or toe cutter if used in tiny volumes. Just make up a 1% solution of it, and then it's very easy to precisely dose out.

Bill Burk · Jul 26, 2020

PB for paper, BZ for film... at least so far.

I used to use pinches of PB in the Dektol 1:2 tray, as if I were feeding goldfish.

The BZ comes in tablets and I mix them up and add to the D-76 1:1 developer in the beaker just before it goes in the tank.

pentaxuser · Jul 26, 2020

MattKing said:
Did anyone else look at the thread title and wonder what David was going to post about peanut butter?

A similar thought struck me, Matt. Whenever I see two initials V two more initials I always think of these spurious boxing matches that are impossible such as Jack Dempsey v, say, Ali and speculating who would win.

pentaxuser

Doremus Scudder · Jul 26, 2020

Many phenidone-based print developers use BTA (BenzoTriAzole) along with potassium bromide to offset the warmish tone the developer gives the prints (ID-62, Bromophen, etc.) I'll often add a bit of BTA to my print developer to cool print tone a bit and clear the whites, often in conjunction with added carbonate. I do this less now that I'm using more VC papers, but it was a real help with graded papers to tweak contrast a bit.

If you want to play with developer formulations, you can substitute BTA for bromide and vice-versa using a factor of 10 (1/10th the amount of BTA as bromide and vice-versa). BTA is best used by making a 1% or 2% w/v stock solution and then using that instead of measuring out the dry chemical each time.

For dealing with paper fog, BTA works, but slows down the paper a lot. I like to use a weak ferricyanide/bromide overall bleach after the fix for fogged paper, sometimes in conjunction with BTA in the developer; sometimes, just to clear the whites a bit with non-fogged paper.

Best,

Doremus

David Lyga · Jul 26, 2020

NB23 said:
Thanks for the good info!

But to be honest, I hope to never have to deal with bad papers again!

Exposing each of the 1000 sheets I had for a
Whole minute to 1:30 (instead of 15-30 seconds), and then developing for 3-4 minutes, instead of the usual 1 minute, really got to me in the end.
And then brown toning just to get acceptable results... it was hard work.

let’s roughly calculate the lost time for, in the end, still subpar results: I process 4 sheets together in each bath.
So 1000/4=250.
250 x 3 minutes extra in the developer= 750 minutes.
Exposing each sheet 1 minute extra = 1000 minutes.
Brown toning for 15 minutes, 50 prints at a time. That’s 20 Sessions of 15 minutes = 300 minutes.

So in conclusion; in order to save roughly 350$ of papers I have lost 2050 minutes (34 hours) working on bad papers.

Yes! I’ve worked 34 hours extra for subpar results, all in order to save 350$. I’ve been quite stupid, if I think of it.

And then, fresh paper is so wonderful!

You have clearly, albeit morbidly, quantified the false economy employed by David Lyga, master of darkroom's daft craft component. However, your 1.5 minutes exposure time sometimes becomes my two or three minutes exposure time, followed by up to five full minutes of developing time. I simply have got to save that old paper because my trash bin will scream at me if I decide to make a marriage with the twain. (With mega-aged paper and film there is a DESPERATE need to hold back threshold density while using yeomen's effort to emphasize contrast.)

Yes, discussions like this are good for theoretical ammunition but those bullets sometimes end up hurting one's sanity and even bottom line. These things are good to know but we must always keep in mind that 'waste' can be defined in more ways than one way. - David Lyga

David Lyga · Jul 26, 2020

MattKing said:
Did anyone else look at the thread title and wonder what David was going to post about peanut butter?

Matt, if my feeble, 70 year old head could dissect the punch line I might, again, call you a very funny man, but, alas, I simply am not able to define the nut butter within my nutty head. - David Lyga

NOTA BENE: A light just sparked in David Lyga's brain. The PB is the butter, (that is what I dare utter).

David Lyga · Jul 26, 2020

Doremus Scudder said:
Many phenidone-based print developers use BTA (BenzoTriAzole) along with potassium bromide to offset the warmish tone the developer gives the prints (ID-62, Bromophen, etc.) I'll often add a bit of BTA to my print developer to cool print tone a bit and clear the whites, often in conjunction with added carbonate. I do this less now that I'm using more VC papers, but it was a real help with graded papers to tweak contrast a bit.

If you want to play with developer formulations, you can substitute BTA for bromide and vice-versa using a factor of 10 (1/10th the amount of BTA as bromide and vice-versa). BTA is best used by making a 1% or 2% w/v stock solution and then using that instead of measuring out the dry chemical each time.

For dealing with paper fog, BTA works, but slows down the paper a lot. I like to use a weak ferricyanide/bromide overall bleach after the fix for fogged paper, sometimes in conjunction with BTA in the developer; sometimes, just to clear the whites a bit with non-fogged paper.

Best,

Doremus

Yes, Doremus, using a weak Farmer's after the fact tends to work wonders. There really is a reason why it has traditionally been called Photographer's Gold.

But, your substitution explanation (PB vs BZ) needs explaining. OK, maybe the substitution which you present is viable, but there ARE formulae which require BOTH. I guess that that is what I would like to ponder. WHY BOTH? Are there aspects of one of these chemicals that the other cannot match? Or, as you seem to infer, they are interchangeable if, simply, only the quantities employed are changed? Or, I have no definitive reason to posit this but: Is there a synergy at work here? Let's delve. - David Lyga

David Lyga · Jul 26, 2020

pentaxuser said:
A similar thought struck me, Matt. Whenever I see two initials V two more initials I always think of these spurious boxing matches that are impossible such as Jack Dempsey v, say, Ali and speculating who would win.

pentaxuser

Or court cases which never get solved ... like this one.

grain elevator · Jul 26, 2020

@earlz, the paper linked in post #6 doesn't seem to report the differences in how BTA and KBr (let's please drop PB, who could want the confusion with peanut butter and lead?) act. Was your post with regard to paper? That could explain it, because the paper is about film.

David Lyga said:
there ARE formulae which require BOTH. I guess that that is what I would like to ponder. WHY BOTH?

Good question. What earlz has posted could explain it. In paper developers, maybe it's because of the relationships with image tone that Doremus has pointed out?
I also wonder if KBr is helpful in developers to be reused, which load up with bromide from the emulsion. If there's already bromide in the developer, maybe the effects of the additional bromide are less dramatic?

David Lyga · Jul 26, 2020

To me, at least, the BZ has always seemed to act against fog in a purer manner. There is no 'greenish' (or so they say) cast to the paper which had used KBr as its restrainer.

I find that the BZ 'goes right to work without hesitation' if you take my advice and increase the HQ, decrease the Metol, and use BZ in limited amounts. Excess BZ will lead to ALL of the silver refusing to be turned into density. - David Lyga

Doremus Scudder · Jul 27, 2020

David Lyga said:
Yes, Doremus, using a weak Farmer's after the fact tends to work wonders. There really is a reason why it has traditionally been called Photographer's Gold.

But, your substitution explanation (PB vs BZ) needs explaining. OK, maybe the substitution which you present is viable, but there ARE formulae which require BOTH. I guess that that is what I would like to ponder. WHY BOTH? Are there aspects of one of these chemicals that the other cannot match? Or, as you seem to infer, they are interchangeable if, simply, only the quantities employed are changed? Or, I have no definitive reason to posit this but: Is there a synergy at work here? Let's delve. - David Lyga

I imagine that print PQ print developers like ID-62 and Bromophen were originally variations on MQ developers, with the Metol replaced by phenidone. Then the image tone was adjusted to give a desired result (likely matching tones already achieved and preferred with MQ developers) by adjusting the ratio of BTA to KBr. KBr is likely much cheaper than BTA, so using as much of it as possible and then cooling the tone with a little BTA makes economic sense for a manufacturer.

Maybe there are other reasons as well.

Best,

Doremus

David Lyga · Jul 27, 2020

I do not really think that KBr is cheaper than BTA. Although that might be the case presumptively, when weight is the only criterion, it is hardly the case as to potency. - David Lyga

PB vs BZ

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