BZT and/or bromide

[Wayne]

Phenidone isnt very responsive to bromide restrainer (or so I hear), so for a print developer with phenidone one should presumably use BZT. But since there is usually another reducer such as C and/or HQ and/or Glycin and/or Metol, and benzotriazole isnt as effective a restrainer as Br (or so I hear), from a fog standpoint should such a developer always contain both Br AND BZT? Or can BZT do the job just fine, with the addition of Br being completely optional, ie to warm the tone? Or does it depend on which of the additional reducers are used?

 

[Ryuji]

It is not true that phenidone doesn't respond to bromide. It does. It is also not true that benzotriazole does not work as an antifoggant in non-phenidone developers.

In commercial print developers, restrainers are selected to meet the requirements such as processing time, replenishing rate, processing capacity, etc. Optimal choice of restrainer also depends on the silver halide composition. For example, for chloride emulsions, 6-nitrobenzimidazole and NaCl are commonly used together for b&w print developers, both in MQ and PQ types.

In film developers, especially when optimal speed and accutance are important, the restrainers are selected with these additional considerations.

If you need more specific info, let me know of your goal and material.

 

[Wayne]

It is not true that phenidone doesn't respond to bromide. It does. It is also not true that benzotriazole does not work as an antifoggant in non-phenidone developers.

In commercial print developers, restrainers are selected to meet the requirements such as processing time, replenishing rate, processing capacity, etc. Optimal choice of restrainer also depends on the silver halide composition. For example, for chloride emulsions, 6-nitrobenzimidazole and NaCl are commonly used together for b&w print developers, both in MQ and PQ types.

In film developers, especially when optimal speed and accutance are important, the restrainers are selected with these additional considerations.

If you need more specific info, let me know of your goal and material.

Just to be clear, I didnt mean to say that phenidone ISNT responsive to bromide or that Bzt DOESNT work with non-phenidone agents. But I've heard (read actually) that the former isnt AS responsive, and the latter isnt AS effective.

I phrased the question very broadly so that I could perhaps learn something about the principles involved for future reference. In the narrowest sense, I was wondering whether a phenidone-glycin or phenidone glycin-HQ print developer should include KBr in addition to BZT. (although your first sentence raises the question of whether Bzt is needed at all, I prefer having some for the cooling effect on warmtone papers).

 

[lowellh]

More to the point, Br is effective in the toe of the curve and BZT is effective in the shoulder.

 

[Ryuji]

More to the point, Br is effective in the toe of the curve and BZT is effective in the shoulder.

That is very hard to generalize. That kind of observations you (or your references) made should be interpreted as a particular case of the emulsion and the developer.

BTA (benzotriazole) can simply shift the curve to the right. I can also affect in the toe. It really depends. On the other hand, Br can affect the Dmax as well, especially in vigorous developers like D-19. Different mechanisms are in effect in each case...

 

[Ryuji]

Just to be clear, I didnt mean to say that phenidone ISNT responsive to bromide or that Bzt DOESNT work with non-phenidone agents. But I've heard (read actually) that the former isnt AS responsive, and the latter isnt AS effective. [\quote]

That's understood from your original post. I've also seen people like Richard Knoppow repeatedly posting stuff like that.

I phrased the question very broadly so that I could perhaps learn something about the principles involved for future reference.

There are two major mechanisms in action of antifoggants. One is electrochemical and another adsorption. Development of a silver halide grain is an electrochemical process; it's like a voltaic cell battery where anode and cathode are shorted. Anode reaction is the oxidation of the developing agent. The anode potential is determined by the developer, concentration, pH, and so forth. These are the reducing property of the developing agents at the particular condition of the developer solution. The cathode reaction is the reduction of silver halide to silver. The cathode potential is determined by the free silver ion in the solution in vicinity of the developing grain. Bromide and organic antifoggants depress the free silver ion concentration in the vicinity of developing silver surface and this modulates the cathode (silver electrode) potential. Addition of Br-, BTA or other antifoggants doesn't change the anode potential (developing agent's reduction potential), but their addition will narrow the gap (called overpotential) so the development reaction will be slower. In well formulated developers, anode potential is several tens of millivolts lower than the cathode potential. This overpotential is most influential on smaller latent images, as large LI doesn't require too much overpotential to develop. Of course, if you increase the overpotential way too much, then the grain will fog, and you'll lose the image-specificity.

The adsorption mechanism is that the surface of grain is covered by antifogging agents. This is at competition with adsorption properties of sulfite, developing agents and other addenda. In terms of adsorption, ascorbate < hydroquinone << metol < phenidone << phenylenediamine derivatives, so phenidone could use a bit more adsorbent antifoggants compared to metol developers, but the difference is small.

In the narrowest sense, I was wondering whether a phenidone-glycin or phenidone glycin-HQ print developer should include KBr in addition to BZT. (although your first sentence raises the question of whether Bzt is needed at all, I prefer having some for the cooling effect on warmtone papers).

I'd use both if you want to keep consistent development time and image hue from the first print to 20th print out of a liter of the developer. Balancing them is also important if you want to get consistent image hue, especially if you tone the print in polysulfide toner.

If you are using an average chlorobromide enlarging paper, the paper will take up a bit more BTA than dictated by the relative concentration of the developer and carryover volume. Also, the paper will release some bromide during development. If you factor these in, you can make a very good replenishing system that lets you print for a very long time without a total replacement of the bath.

 

[Wayne]

Thanks for the explanation. Perhaps I have heard RK mention the insensitivty of phenidone to KBr before, but on this particular occasion it from a former r.p.d. denizen named Walt Brand. In regards to ID-62 PQ developer he said

"Phenidone tends to ignore bromide, but it does take notice of benzo, and
you definitely don't want fog in your prints. The KBr is probably in
there to keep the tones from going too cold; you could eliminate the
KBr if you like cold tones. "

And in fact thats what I have done. I've used it a fair bit with no KBr with no apparent ill effects, but then I'm not exactly Ansel Adams.

My developer has glycin in it too though. Anchell says "glycin is very sensitive to bromide" or words to that effect (the books is upstairs and I'm lazy.)
What exactly does that mean, in practice? Should I be careful of using too much KBr if I decide to add it (my tendency is not to add it, since it seems to work w/o)

 

[Ryuji]

I would not say that at all. Addition of bromide in phenidone developer containing benzotriazole would not make the image warmer toned. There are lots of bulls circulated about warmtone, bromide, etc. The reason you want to have both KBr and BTA is consistency of the speed, processing time, hue, and other factors throughout the processing capacity of the developer solution. As these agents are used in less than 1% quantity in commercial developers, amateurish analysis of MSDS will most likely miss the importance of those agents. I have also been trying several antifoggants and hue modifying agents in print developers as well.

 

[Wayne]

Well maybe I will try some KBr in this batch I'm mixing tonight.
As long as you are reading this, maybe you can comment on the following.

I used the ID-62 formula as a loose basis for a phenidone-glycin-HQ version of Ansco 130. (why i didnt just use Ansco 130, I dont recall). I reduced the phenidone to .2 g though, because ID-62 calls for .5 gram and .2 g seemed like a more appropriate equivalent for replacing the 2.2 grams of metol in Ansco 130.

Would that extra .3 g of phenidone make it better in any way, or would it just be a waste or worse?

 

[Ryuji]

ID-62 developer formula containing 0.5g/L phenidone is designed to be used at 1+1 to 1+3 dilution. Doesn't that answer your question? At the working strength, phenidone would be 0.125 to 0.25g/L.

 

[Wayne]

I guess what it boils down to is, how much phenidone is necessary when you also have glycin in addition to the HQ? How would the developer change if I used .5 gram instead of .25? Would it mostly affect the speed, capacity, contrast, all or none of the above? Since I use the glycin and HQ amounts that Ansco 130 uses and that developer is usually used only 1:1 or 1:2, is there any benefit to using .5 gram instead of .25? I'm curious enough now to just try it, but I'm still interested in the theoretical consequences too.

 

[Ryuji]

If you add phenidone, that agent will be primarily transferring electrons to the developing grains. Then the agent that is most effective pair to phenidone in terms of superadditivity will be consumed from the developer. That'll be hydroquinone. I don't think presence of glycin is essential or terribly helpful in this situation.

Addition of phenidone probably doesn't change much, or not at all, on the processing capacity.

Difference on dilution can affect the processing capacity, processing speed, image hue, possibly on the curve shape in the shoulder region, etc. However, a larger difference will come when the test prints are toned in polysulfide toners. I've seen many cases when difference is barely discernible to my eye before toning making drastic difference after toning in my homemade polysulfide-selenium combination toner.

 

[Wayne]

I dont have any interest in losing the glycin from the formula, but I do leave out the HQ sometimes. Is there an optimal ratio of phenidone to glycin?

 

[Maine-iac]

I would not say that at all. Addition of bromide in phenidone developer containing benzotriazole would not make the image warmer toned. There are lots of bulls circulated about warmtone, bromide, etc. The reason you want to have both KBr and BTA is consistency of the speed, processing time, hue, and other factors throughout the processing capacity of the developer solution. As these agents are used in less than 1% quantity in commercial developers, amateurish analysis of MSDS will most likely miss the importance of those agents. I have also been trying several antifoggants and hue modifying agents in print developers as well.

Ryuji, over the years when I wanted to use benzotriazole in a formula, I've opted for Edwal's Liquid Orthazite. Recently, I heard a rumor that Orthazite is not pure benzotriazole but may contain some bromide as well. Do you know whether that is true? Have I been using a mix of bzt and br all these years?

Larry