I do quite a bit of bleaching using a potassium ferrocyanide/potassium bromide rehalogenating bleach.
My experience is that, unless the bleaching is severe, most papers do not change appreciably in image tone if you proceed carefully. The same goes for when I used ferricyanide alone or with fixer added (Farmer's Reducer).
You do have to re-fix and wash adequately regardless of the bleaching procedure you use.
In case you are interested, here is my procedure:
Note: this technique turns silver into invisible silver bromide that needs to be fixed away. However, you can redevelop (to a certain extent) if you bleach too far by simply returning the print to the developer before the fixing step. However, since the halides formed by the bleach are different from the original, there can be a change in image tone of the bleached/redeveloped area. Sometimes it is just fine, sometimes it is different enough to ruin a print. It depends on how much redeveloping you do and the original composition of the paper.
For local bleaching, I prepare a dilute ferricyanide/bromide solution of about 2% by adding 10 drops of 10% ferricyanide solution and 30 drops of 3.2% potassium bromide solution (I have these on hand always) to 10ml water, or equivalent for larger batches. (You can mix the appropriate dilution in larger quantity for overall bleaching, basic solution is 1g pot. ferricyanide and 1g pot. bromide / liter). This solution is a starting point and can be strengthened or weakened as needed. You can keep the solution until it changes color to green from the original yellow. Life is shortened if the solution is contaminated by fix.
I use everything from Q-Tips to Japanese calligraphy brushes for local bleaching, sometimes even a paper towel dampened in the bleach. I like to work very slowly. I slap the print to be bleached onto the back of a tray that has been propped in the sink, so it is at an angle. With bleach in one hand and water hose in the other, I apply bleach to the area I want while keeping the water trained on the print just underneath that area to prevent streaking.
A bit of bleaching, then a rinse, then 30 seconds or so in the fixer, then another rinse in a tray of running water; repeat as needed to gradually get the effect you are looking for.
I find that with the rehalogenating bleach, the bleaching slows down after a couple of applications if you don't fix out the rehalogenated silver. That said, make sure that you haven't overdone it before the fix step.
That's a "nutshell" explanation of what I do, but bleaching is really an art. I find that I can minimize changes in image tone by going slowly and making sure not to tone too much later (often, the bleached areas will tone differently). And, as I said, some papers are better than others in this regard.
Have fun,
Doremus
www.DoremusScudder.com
