Re: Modifying bleaches

On Wed, 1 Dec 2004, Charlie Goodwin wrote:
>
> Given Judy's experience that the DuPont 6-T Toning System didn't give
> the advertised diverse results, I will not expect that all this will
> perform miracles with all papers, maybe none.

It occurs to me that I should probably mention that all my tests were on
Brovira (old #6, new #5), which was known as being resistant to toning,
which was in fact why I got into bleach and redevelop, which it would do.
Which is to say, your paper may respond better.

> No-one has reacted with horror that the useage of muriatic in Varigam
> Toning Bleach 6B-3 will cause me great harm, other than the caveat that
> proper storage is a must.

And about the poison gas from K ferricyanide -- don't worry about not
smelling it. My experience with it is not that it sort of silently
accumulates and then one day you keel over, like, say mercury or lead in
the blood. But that it accumulates in a tray you've let stand with some
funky additives in it, then you take the cover off and get a lungfull. It
probably has no odor, but your lungs say you've died and gone to hell.

The good news, at least in the couple of times I did this, is that after
you rush out of the room gasping and wheezing into (relatively) clean air,
your lungs will recover, the pain will subside, and -- as far as I can
tell -- no residual damage.

Judy

>
> Further, it sounds like the chemistry is somewhat flexible
>
> So, now I will take, for example, Bleach 6B-3 to be:
>
> Potassium Ferricyanide 22g, give or take, or other bleaching agent, to be tested
> Sodium Chloride 35g, give or take, to be tested
> some strongish acid in some amount to be tested
> Water to make 1000ml
>
> And that consistent, methodical, usage and good note taking are the way to go.
>
> Thanks again,
>
> Charlie
>
>
>
>
>
>
>
>
>
>>>>>>>>> I have become interested in the, new to me, subject of rehalogenating bleaches, both for the flexibility they appear to offer for toning, and for the potential to "turn" a paper of whatever flavor, bromide, chlorobromide or chloride, into a bromide paper or to a chloride paper, or an iodide paper etc.and to redevelop it as such, and also to be able start with a paper as whatever it is, and then to tone it as whatever else I might want it to be. Seems awfully adaptable.
>
> I have no knowledge of the chemistry of bleaches, and wish to proceed safely. I am hoping more knowledgeable persons could tell me that either my guesses are correct, or if I am off base, to tell me what I need to know.
>
>> From browsing the web and scanning through "The Darkroom Cookbook" it appears that the keys to rehalogenating bleaches are a bleaching agent and a source of a halogen, chlorine, bromine or iodine.
>
> The bleaching agent seems to need to be potassium ferricyanide, or maybe Potassium permanganate, or a dichromate. Unless I am told I really need something else, just from a safety standpoint, ferricyanide looks like my choice.
>
> And then a halide source, potassium bromide, potassium iodide or sodium chloride
>
> I found in "The Darkroom Cookbook" a bleach called a rehalogenating Bleach and several very similar looking bleaches like the DuPont 6-T Toning System, which deploys three different bleach baths for varied effects:
>
> Varigam Toning Bleach 6B-1
> Potassium Ferricyanide 22g
> Potassium Bromide 25g
> Water to make 1000ml
>
> Varigam Toning Bleach 6B-2
> Potassium Ferricyanide 22g
> Potassium Iodide 10g
> Water to make 1000ml
>
> Varigam Toning Bleach 6B-3
> Potassium Ferricyanide 22g
> Sodium Chloride 35g
> Nitric acid 15ml
> Water to make 1000ml
>
> These are ordinarily followed by toning baths.
>
> I presume these Varigam Toning Bleaches are all rehalogenation bleaches which could be used to reduce a print back to a silver halide and followed by a simple redevelopment in one or another common developer.
>
> My initial question is that I wonder if chloride rehalogenating bleaches like Varigam Toning Bleach 6B-3 could be modified by using hydrochloric acid rather than nitric acid.
>
> That quickly becomes several related questions. Would it be safe to do so? Would it work well? I am hoping to use, wherever practicable, common household chemicals or commonly available items like muriatic acid. If I can get along well without ever needing nitric or sulfuric acids and super concentrated acids I would be glad. But, if I do need to use nitric or sulfuric acids, can they and should they be obtained in lower concentrations? Would that create other issues? Cost is less an issue than safe handling.
>
> Reading about ferricyanide bleaches, the precautions I see say that ferricyanide is generally not a dangerous source of cyanide gas unless it is mixed with strong acids. I am guessing that the 15ml of nitric isn't enough to create that hazard. I hope I can use hydrochloric in a similarly safe manner (or safer). I don't want to mess around with safety on this one.
>
> Thanks in advance!
>
> C
>>>>>>>>>>>>>>>>>
>
Received on Wed Dec 1 22:22:12 2004