Will the real Farmer's Reducer formula please stand up?

[Steve Goldstein]

The versions of this formula in the Darkroom Cookbook (both 3rd and 4th editions) lists 60.0 grams of Potassium ferricyanide and 30.0 grams of Potassium bromide in water to make 250ml for Solution A. Most of the internet sources I've looked at recently call for 64.0 grams of Potassium ferricyanide instead of 60. I know the difference is inconsequential, but I'm curious which amount is "right". Inquiring minds, too much time on my hands, whatever...

 

[paul ron]

Best way to find out is to try both n see what works better?

Hope you'll tell us?

 

[Gerald C Koch]

There was a similar thread some months ago. It seems to bother people if there is not a definitive formula that can be pointed to. Strictly speaking what you describe is not Farmer's reducer which does not contain any bromide. Addition of the bromide makes it a rehalogenating bleach. To further complicate things, Farmer's can be used as either a single or two bath reducer. However many photographers make up a working solution of the bleach extemporaneously based on its color. Thus Ilford's instructions for IR-1. To the thiosulfate solution add just enough of the ferricyanide solution to color it a pale yellow.

 

[Kevin Caulfield]

I'm impressed by the use of the word "extemporaneously".

 

[Ian Grant]

Farmer's Reducer (Agfa Ansco)

Solution A
Sodium Thiosulphate 240g
Water to 1 litre

Solution B
Potassium Ferricyanide 19g
Water 250ml

To use 1 part Solution B, 4 parts Solution A, plus 32 parts water. Solutions 1 & 2 should be kept separately and mixed just before use.

Kodak publish two versions, R-4a is used like the Agfa Ansco version, and R-4b which uses the Ferricyanide solution first then immersion in the Thiosulphate.

The reason for adding Bromide is when bleaching with a Ferricyanide/Bromide solution mistakes can be corrected before the Thiosulpahe bath by washing and re-developing. I tended to use a bleach with bromide because I also used the same bleach for selective toning as part of hand colouring prints. We used the bleach at work for graphics work as well.

Ian

 

[Steve Goldstein]

"Farmer's" certainly seems to have picked up a lot of variations over its long lifetime including, apparently, the addition of KBr in the Darkroom Cookbook and many other places. I should clarify that the formula I was asking about is for print reduction, not for use on negatives. My question was motivated by a discrepancy I noted in nearly-identical formulae from several sources. I realize that this formulation isn't terribly critical and I'm not worried about having the "right" formula down to the microgram.

Let me change directions a bit... What benefit does the KBr provide for bleaching prints when ferricyanide and thiosulphate are combined in a single bath? Wouldn't the presence of fixer make the bleaching action irreversible, preventing the possibility of redevelopment? Why add the halogen?

Ian - in your post you list Solutions A and B in the recipe, but you refer to Solutions 1 and 2 for usage. I assume 1=A and 2=B, that would seem to be the right relative proportions...

Steve

 

[Ian Grant]

Thanks Steve I've edited and corrected.

There's no definitive Farmer's reducer formula but none contain Bromide. The earliest reference I have to it is quite vague in a 1921 BJP Almanac.

EH Rarmer's Reducer, a Hypo solution 1:5 with water 150ml and add sufficient 10% solution of Potassium Ferricyanide, best judged by the colour of the solution which should be pale yellow not orange.

There's comments about yellow staining if acid fixer or an old (used) fixer bath is used instead of a fresh Hypo bath. I would assume the Hyo solution would be the common 240g/litre plain Hypo (Sodium Thiosulphate) fixer. It's because it's vague that every company made slightly different versions.

If you are using it mixed with the Hypo then there's no possibility of re0developingl when bromide is in the Ferricyanide solution, so there's no benefit adding it. Many people with have a stock solution of Ferricyanide/Bromide on their shelves anyway so just use a few drops in a reducer.

Ian

 

[Ian Grant]

Just to add I found an earlier reference to Farmer's reducer 1898:

Under "Negative Reducers"

Farmer's Reducer
Saturated solution of Potassium Ferricyande 1 part
Hypo solution 1:5 10 parts

No instructions for use but later in the same BJP Almanac there's a comment about using Farmer's reducer after Uranium toning prints, using Hypo solution dilute 1:10 then adding just enough Ferricyanide solutution (strength immaterial) to the hypo solution to form a lemon yellow solution.

Ian

 

[David Lyga]

WOW, so much technical accuracy for such an easy process. Here is what David Lyga does (and I am not a neophyte).

By volume, not mass: 3 ml potassium ferricyanide for each 100ml of water. That is your bleach. Keeps indefinitely in a closed bottle.

Mix one part bleach + one part film strength fixer for the most powerful reducer. Freely dilute this mixture with water (even up to 20 times the combined volume) to slow down the reduction process.

That is all there is to it. Understand that combined, the reducer does not last long. When diluted, it does last longer, however. - David Lyga

 

[RalphLambrecht]

The versions of this formula in the Darkroom Cookbook (both 3rd and 4th editions) lists 60.0 grams of Potassium ferricyanide and 30.0 grams of Potassium bromide in water to make 250ml for Solution A. Most of the internet sources I've looked at recently call for 64.0 grams of Potassium ferricyanide instead of 60. I know the difference is inconsequential, but I'm curious which amount is "right". Inquiring minds, too much time on my hands, whatever...

I'd trust the darkroom cookbooks.

 

[Ian Grant]

WOW, so much technical accuracy for such an easy process.

The commercial companies added the accuracy. Farmer himself just said dilute some fresh plain Hypo Fixer by 1:5 with water and add the Ferricyanide solution by eye. So yes such an easy 1883 process

It's not a good idea to use modern rapid fixer as that makes reduction very much faster and less controllable.

Ian

 

[David Lyga]

It's not a good idea to use modern rapid fixer as that makes reduction very much faster and less controllable.

Ian

I handily succeed with the rapid by diluting yet more. The same result results. - David Lyga