Bleaching Overexposed Negatives

[alkos]

The problem is that the Iodine dissolves the silver and removes it from the emulsion without forming insoluble silver Iodide.

Interesting! So is the fixer necessary at all? What is the orange stain that stays after iodine bleaching and is it permanent when fixer is not used?

OTOH, I have just successfuly redeveloped the image in the thioruea... but not in the conventional dev.

[Ian Grant]

Iodine stains prints/negatives, trays etc.

Iodine/Iodide bleaches are normally used as cutting bleaches for total removal of silver to a white base on prints.

Ilfor IR-4 For local and general reduction of prints

Potassium Iodide 16g
Iodine 4g
Water to 1 litre

To use dilute 1+19 with water.

Re-fix in a 20% Plain Hypo fixing bath.

I used this bleach quite extensively in the 70's & 80's for commercial work, it stains the base of papers, but the stain goes entirely if you place the print in dilute developer. Try cleaning the Iodine stains in your tray by leaving used dev in it overnight.

It may be the Silver Iodide on it's own isn't that light sensitive which is why it doesn't re-develop, thiourea or sulphide actually fog the silver halide in the emulsion. Thiourea has been used in B&W reversal processing to allow the elimination of the reversal re-exposure to light.

Ian

[Lyn Arnold]

I came across this post when searching for a solution to my problem of over-exposed Tri-X negs.

I used Ian Grant's suggestion of bleaching in Pot Bromide 1% and Pot Ferricyanide 1%.

After 10 minutes, the negs just looked a dense battleship grey, with no definition. I washed them, put them in to a dilute X-tol bath (1+19). The negs returned to their black state with some definition. When nothing further happened, I washed them and put them into Hypam. Whoosh! Negs became clear with an orange/brown tint, and not a thing on them!!

What went wrong???

Help would be most appreciated -- not for these poor things, but for the next time I find myself with overexposed negatives.

Thanks

[Doremus Scudder]

I'm sure Ian will chime in here too.

What I think has happened is that your negative was not redeveloped. It seems you just bleached and then cleared in the fixer...

A couple of things could have caused this. First, you could have not had enough bromide in your bleach solution to actually rehalogenate the image silver, just bleach it to a fixable state. It has to be converted to silver bromide.

Or something else went wrong in the bleaching step. You are using one solution of ferricyanide and bromide, not two baths, right? FWIW, I rather regularly use bleach-redevelop to add a bit of contrast. The negatives should bleach to film-base clear, not "dense battleship grey"... This makes me think that something went wrong in the bleaching step.

Second, you may have not left the negatives in the developer long enough to develop properly. (How long did you develop?) Then, you fixed out the undeveloped image in the fixer. Or, maybe you didn't get the negative exposed after the rehalogenation. You are exposing the negative to bright white light, right?

With my pyro negs, the silver bleaches away completely, leaving a faint pyro stain image and a clear film base. Redeveloping in a staining developer to completion adds another layer of stain, thus increasing contrast a bit. For reducing contrast, you should develop by inspection to the desired contrast.

For cutting overall fog, using Farmer's Reducer and pulling the negative when the desired amount of density has been removed may be a better choice than bleach-redevelop.

Farmer’s Reducer for Negatives
(Kodak R-4a negative reducer. Cutting formula for overexposed negatives)
Stock Solution A:
Potassium ferricyanide 19 g
Water to make 250 ml

Stock Solution B:
Sodium Thiosulfate (hypo) 240 g
Water to make 1 liter

For use, mix 30 ml. Solution A with 120 ml. Solution B and add water to make 1 liter. This is for cutting the density of negatives, but it also increases contrast.

Farmer’s Reducer for Negatives
(Kodak R-4b negative reducer. Proportional formula for overdeveloped negs)
Stock Solution A:
Potassium ferricyanide 7.5 g
Water to make 1 liter

Stock Solution B:
Sodium Thiosulfate (hypo) 200 g
Water to make 1 liter

For use, place negative in solution A for 1 to 5 minutes, then place in solution B for 5 minutes.
Wash thoroughly.

Note that the first formula is the one to use for cutting overall density. The second formula is just fyi. You would probably be better off with bleach-redevelop for overdeveloped (i.e., too contrasty) negs.


Best,

Doremus

www.DoremusScudder.com

[Lyn Arnold]

Thank you Doremus for taking the time to reply to my post. That news is great. I have some older negs from the Holga that have been overexposed, so will practice on those.

kind regards,
Lyn