The sepia tone bleach I have purchased from Kodak contains only Potassium Ferricyanide, so it just part A of Kodak's Farmer Reducer.
Are 110% sure, it not viable.
Originally Posted by Greg Davis
What? Are you saying that it isn't viable, or not available? While Kodak doesn't sell it anymore, some stores here still have old stock on the shelves. The bleach portion is packaged separately and is clearly labeled as potassium ferricyanide, as is one of the two packets that make up the Kodak Farmers Reducer that I have on my shelf.
The Ilford manual states (not that you should believe anything you read) –
Stock bleaching solution
Potassium ferricyanide 25g
Potassium bromide 25g
Water to make 250g
I have used this and it works fine.
“The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”
The formula that I have for Farmer's Reducer is:
Potassium Ferricyanide 19 g
Water 250 ml
Stock Solution B:
Sodium Thiosulfate 240 g
Water 1 litre
Mix 30 ml of Solution A together with 120 ml of Solution B and then add water to make 1 litre of working solution.
A popular variant of the Farmer's Formula purely for use with prints as it is a re-halogenating version of the reducer (which means that, if you over bleach the print you can return it to a developer and build up the density once more).
Potassium Ferricyanide 64 g
Potassium Bromide 30 g
Water 250 ml
Sodium Thiosulfate 120 g
Water 500 ml
For controllable use you mix 7.5 ml of Stock A together with 180 ml of Stock B and add 750 ml of Water.
The formula that I have for a PROPORTIONAL reducer is:
Potassium Ferricyanide 7.5 g
Water to make 1 liter
Sodium Thiosulfate 200 g
Water to make 1 liter
You place your print/negative in solution A for 2 to 5 minutes and then you place it in solution B for 5 minutes followed by a very thorough wash.
The Adams' formula that I have used most myself (albeit long ago when I had no choice but to use old paper) to clean up veiled/very slightly fogged highlights or to boost the whites of people's eyes in commercial portraits, etc):
Thiourea 15 g
Sodium Thiosulphate 700 g
Water 1 Litre
Potassium Ferricyanide 75 g
Water 250 ml
To make a working stock (does not keep long) you add 5 parts of Solution A to 14 parts Water (Working Bath A) and then combine Working Bath A with an equal quantity of Stock B.
Many people get happily by with just using the simple Farmer's Formula but I am aware of many friends who have been plagued by intermittent yellow staining / over bleaching / etc who have moved to either the Potassium Bromide variant of the Farmer's Reducer or, more often, to Adams' Thiourea formula.
Hope that helps.
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Am I correct that if one uses the Bromide+Thiosulfate version of Farmer's reducer, that the print must be fixed afterwards?
Trying to be the best of whatever I am, even if what I am is no good.
You should re-fix after any reducer. The problem is the ferricyanide breaks down the thiosulphate so you might not completely remove the bleached silver without re-fixing.
Yes, anytime the image silver is bleached or rehalogenated, it must be fixed out or it could (will) cause staining later.
Originally Posted by Ian Grant
FWIW, I think we need to distinguish between ferricyanide/thiosulfate bleaches (Farmer's, etc.) and the rehalogenating bleaches, which contain bromide.
What is clouding the issue, I believe, is that you can add thiosulfate to rehalogenating bleaches to speed up the bleaching process (creating a sort of hybrid). However, I use a simple potassium ferricyanide/potassium bromide rehalogenating bleach for both negatives (bleach/redevelop) and prints (both local and overall bleaching) with good results. No thiosulfate at all in the process. I find it more controllable (not to mention reversibly to a certain extent) than Farmer's Reducer.
Bromide in the bleach makes a rehalogenating bleach, as Gerald points out. I works similarly to other ferricyanide bleaches but can be reversed to some extent and some, like myself, find it more controllable.
Bromide in developers acts as a restrainer and helps prevent fog. It warms image tone a bit in print developers.
Benzotriazole is an organic anti-foggant, works differently chemically than bromide, but accomplishes much the same thing; a reduction in fog. I cools image tones in prints somewhat.
Many fine-tune the proportion of bromide and BZT in their print developers to control image tone.
I'm not sure of the differing roles of bromide and BZT in formulating negative developers. I suspect it is more complex than my current knowledge. I do know that phenidone developers do not react as well to bromide in the formula and, therefore, BZT is usually used as a restrainer if one is needed (the same would apply to print developers also I suppose).
Last edited by Doremus Scudder; 03-27-2013 at 07:49 AM. Click to view previous post history.
Thank you all, especially David Allen, Ian Grant, and Doremus Scudder. You have helped to clarify this, especially with the re-halogenation part.
If there are further comments, speak. - David Lyga
Originally Posted by Doremus Scudder
I want to slightly lighten some parts of my prints on FB warmtone paper and I want a simple reducer formula for that. What's your bromide/ferricyanide formula and how do you use it? Also, if I use only a ferricyanide solution and then wash and fix, will the prints be more prone to strains? (I will selenium tone them subsequently in strong KRST solution for long time).
Thank you in advance