another bleaching question

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In making one's own bleaching solution, I have found different formulas. Can you use just the Ferri or do you have to add the Potassium Bromide. If anyone has measurements in teaspoons, as opposed to grams (I don't own a scale), that would be helpful. I have been reusing solution A and B. I discard A when it turns green, but how do you know when the plain hypo is exhausted? I water bath between each process so as not to contaminate each solution. Thanks for the help. carol

-- carol maurin (cbmaurin@earthlink.net), December 27, 2000

Answers

According to Lootens, "The addition of potassium bromide is ... unnecessary but it restrains the subtractive action and also prolongs the life of the reducer by about 30%." Solution B is simply a 25% solution of hypo, which in my experience doesn't keep well at all-- maybe a couple of months.

Are you bleaching film or prints? I have two different formulas on my site: the one for film eliminates the bromide and uses a less concentrated ferricyanide mixture, but calls for more of it when the two are mixed. Both formulas call for mixing a certain ratio of A and B for reduction. The mixture only lasts an hour or so.

It is perfectly feasible to mix it as you go. For prints I think you could get away with 10 teaspoons of hypo and a half-teaspoon of ferricyanide for a liter of solution, but I would then recommend re- fixing in your regular fix (after a thorough wash).

My understanding is that the ferricyanide turns the silver back into a silver halide, and the hypo then removes the halide. That is why if you bleach only, you can then redevelop with either an ordinary developer or with sodium sulfide (as in sepia toner). The addition of bromide is recommended if you wish to redevelop, as it also provides extra material for the formation of silver halide.

If you use the solutions separately, it seems to me you run the risk of easily over-bleaching, but ultimately whatever works for you is fine.

http://unblinkingeye.com/Articles/Developers/Formulas/formulas.htm

-- Ed Buffaloe (edb@unblinkingeye.com), December 27, 2000.


I realize I mis-read your question. Regular sodium thiosulfate fixer is only good for fixing about 30 8x10 prints per liter, with fixing times increasing as you proceed. This assumes that the paper has a lot of unexposed/undeveloped silver halides to be removed. I would guess that a bleached print has less, but it would of course depend on the extent of the bleaching. I also don't know how plain hypo compares to regular sodium thiosulfate fix (which has other components) when it comes to longevity. I would use the hypo for about 30 prints, but I would also recommend re-fixing in whatever your regular fixer is after washing, just to make sure there are no lingering silver halides.

-- Ed Buffaloe (edb@unblinkingeye.com), December 27, 2000.

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