help: bleach/pot ferri/farmer's reducer - what's the difference?

[audible]

i've been reading about using a bleach to lighten highlight areas, especially those not easily dodged. but i'm a little confused about what to use...

should i be trying to find farmer's reducer? potassium ferricyanide?
what's the difference anyway?

if i'm not wrong, what i want is something that lightens highlights more than shadows, increasing contrast.

here's what i've found on sale... which is it i'm after?
reducers from silverprint
farmers from the formulary
pot ferri from the formulary

:confused:

 

[David A. Goldfarb]

Potassium ferricyanide is a bleach that is used in combination with fixer to clear the bleach, and this combination is called Farmer's Reducer. When it is packaged together, it's more suited for general bleaching.

For local bleaching, I usually just mix a weak solution of potassium ferricyanide in a cup and a tray of fixer.

 

[Monophoto]

You can make a career out of image reduction technology. Fundamentally, Farmer's reducer is a bleach that is made by mixing potassium ferricyanide and potassium metabisulfite and (classically) ammonium thiosulfate. It is a proportional reducer, meaning that it tends to work faster on highlights. But it is possible to bleach a print down to blank paper if you are inclined to be destructive. Kodak used to offer a packaged version consisting but I haven't seen it for years.

You can accomplish the same effect using plain potassium ferricyanide. Mix up a small very amount with plain water - you want to make a solution that has a faint color similar to weak tea. It doesn't have a long shelf life, so mix only what you need immediately. I saw one old-time photographer who would fill a small, one-ounce graduate about half full with water. He would then moisten a swab in the water, touch the dry ferricyanide with the swab to pick up a few grains, and then swirl the swab in the water to create mix. Some darkroom gurus add a small amount of whatever fixer they happen to be using. That isn't essential, and it does shorten the working life of the solution.

Soak the print in fixer. Lift it out, and while holding the print over the fixer tray in good light, blow the liquid off the face of the print. Apply the reducer to the areas that you want to lighten using a swab or small brush. After a few seconds, put the print back into the fixer to soak some more. Repeat the process until you achieve the degree of reduction you desire. Be careful to reduce in small bites - if the reducer is too strong, it will work too quickly, and once the image is gone, it's gone forever and you have to start over on a fresh print.

 

[audible]

thanks for the answers guys.

looks like the potassium ferricyanide will do.

another question though: is it true that bleach has little effect on RC prints?

 

[DaveOttawa]

Yes, bleach works on RC paper

At least I have found it to do so on Ilford paper.

 

[audible]

thanks dave.

 

[Rich Ullsmith]

I have never understood the purpose of using a bleach along with fixer instead of a rehalogenating bleach, mainly KBr/ferri. Get the reduction where you want it, then fix it. If you go to far, simply redevelop it. If no halide is present and the bleaching goes too far, poof, it's gone.

 

[gainer]

I have never understood the purpose of using a bleach along with fixer instead of a rehalogenating bleach, mainly KBr/ferri. Get the reduction where you want it, then fix it. If you go to far, simply redevelop it. If no halide is present and the bleaching goes too far, poof, it's gone.

If you get too much reduction, redevelop BEFORE you fix it. I'm sure you know that, but the way it was worded was ambiguous.

It is said that the ferricyanide and fixer can be used as a mixture or in succession. One way reduces contrast in the print, the other reduces density. I don't remember which is which, but it's in the Darkroom Cookbook.

 

[phritz phantom]

It is said that the ferricyanide and fixer can be used as a mixture or in succession. One way reduces contrast in the print, the other reduces density. I don't remember which is which, but it's in the Darkroom Cookbook.

there is a difference? i thought the only difference in using pot.ferr. is that it's permanent (no re-developing possible) and that it works faster than pot.ferr without fixer.
is there really a difference in effect/look?

after many otherwise good prints in the trash can, because i stained or overbleached, i now about to start bleaching (again) with only pot.ferr. i'm quite curious and hopeful this will solve a few of my problems.

 

[Ole]

... It is a proportional reducer, meaning that it tends to work faster on highlights. ...

A proportional reducer is one that works equally on all tones (in a fixed proportion to the original silver present). A cutting reducer reduces all tones by the same amount of silver, thus working faster in the highlights.

You can redevelop a print that's been bleached in potassium hexacyanoferrate ( = potassium ferricyanide) even without KBr. You also get different effects (colours) depending on the relative amounts of KBr / KCl / KI.

If you don't use a fixer after partial bleaching, the bleached areas will eventually darken again.

 

[dancqu]

You can redevelop a print that's been bleached ...

If you don't use a fixer after partial bleaching, the
bleached areas will eventually darken again.

I'd suppose that redevelopment would follow exposure to
perhaps an over-head light. Dan

 

[Ole]

Depending on the deeloper, reexposure may not be needed.

 

[catem]

Hi,

If you use toning kits e.g. the Fotospeed Sepia, the bleach in the kit works well for this, as long as it is highly diluted - higher than suggested on the bottle - similar to how you'd use it for partial, or split toning. It's best to experiment, the amount & time depends on the paper & freshness of the solution. For this kit for my requirements I use approx 5 caps to 1800ml water.

If you don't tone after, you have to fix the print, as had been said.

 

[audible]

interesting. what if you bleach to lighten highlights then want to tone in selenium after?

is the sequence: bleach > fix > wash > tone > wash > dry?

 

[dancqu]

I just posted on the thread "Alkali stop an fix ... "
May wish to give my post a read as it deals with
the chemistry of ferricyanide. Dan