Bleach Formula

[Renato Tonelli]

Can some good soul tell me:

1. Bleach formula is for the Kodak Sepia Toner, part A Bleach? ... Potassium Ferricyanide and Potassium Bromide ... in what quantities for 1 liter?

2. How much do you dilute it when split-toning? (Selenium)


Misplaced! Can't find it! Embarrassing...I wrote it down several years ago when I used it often for Se split-toning Agfa Multicontrast.


Thank you

 

[Vlad Soare]

This is what I use for sulfide toning:

potassium ferricyanide 50g
potassium bromide 10g
sodium carbonate 17g (anhydrous) or 20g (monohydrate)
water to make 1 liter

I use it undiluted if I want to tone to completion, or diluted 1+1 if I want to split tone.
This bleach is part of the Agfa/Ansco 221 toner. I don't know what Kodak's formula is, but this should work just as well.

 

[Mark Fisher]

I use 100g KBr and 100g pot ferricyanide to 1 liter of water...or the regular Sepia II bleach. With the home made, I dilute it heavily depending on how I want to use it. 1:10 is reasonable for warmtone papers. Most neutral papers are more resistant to bleaching. For split toning, I'd suggest going with a very heavy dilution 1:25 or more. If it takes too long, add more stock. The regular sepia II pre-packaged bleach seems way more dilute to begin with an I use it at a 1:2 dilution. You'll figure out what works for you and your paper pretty quickly

 

[nworth]

There are about as many bleaches for sepia toners as there are toners. They all work, with somewhat different results. The consensus seems to be about 30 g of potassium ferricyanide and 30 g of potassium bromide to a liter of water. The recommendations vary a lot, and the amounts affect the speed of the bleach. Anything from 10 g of each (Ilford IT-1) to 100 g of each is listed. A popular variation is to add an alkali to the bleach. Ansco 221 uses 50 g of ferricyanide, 10 g of bromide, and 20 g of sodium carbonate; Dassonville T-1 uses 33.5 g of ferricyanide, 15 g of bromide and 7.5 g of carbonate; DuPont 4a-T uses 33.5 g of ferricyanide, 27.4 g of bromide, and 4 ml of ammonium hydroxide. You can see how different these bleaches can be. DuPont 6B-2 is 22 grams of ferricyanide and 10 g of potassium iodide. The most complex bleach I've seen is for Kodak T-7a: 75 g potassium ferricyanide, 75 g potassium bromide, 185 g potassium oxalate, and 4 ml of acetic acid (diluted 1+1 for use).

 

[Vlad Soare]

I believe the carbonate doesn't actually play any active role in the bleaching process. Its purpose is to swell the emulsion to facilitate the removal of the ferricyanide from the paper. One can get nicer, deeper browns by making sure all traces of ferricyanide are eliminated before the toning.