Bleach for black and white prints

[Doremus Scudder]

SLIMT bleaches are very weak. You can use the same proportions of ferricyanide and bromide, but you'll have to mix a bit stronger bleach. Experimentation is in order

Doremus

 

[Fredrixxon]

It's not very critical

Great, but please, give a hint where to start
5g/5g per 1L would be ok?

 

[koraks]

Yup, that should get you started. If that's too slow, double it.

 

[tykos]

SLIMT bleach is (well, all the papers i've read don't provide clear and definitive informations but are more of a "this thing works, but you have to find it for yourself", so the proposal is) 10 parts of pot-ferricyanide and 3.3 parts of pot-bromide.
The proposal is indeed to use them veeeeeery diluted, probably because the technique is mainly directed towards films and not paper.

Curiously, Kachel writes "DO NOT use potassium bromide with B&W papers. It is not necessary and will in fact cause problems.". No further explanations, don't know if it may pose a problem for the techniques or ruin the paper.

 

[koraks]

SLIMT bleach is (well, all the papers i've read don't provide clear and definitive informations but are more of a "this thing works, but you have to find it for yourself", so the proposal is) 10 parts of pot-ferricyanide and 3.3 parts of pot-bromide.

Yes; when I experimented with SLIMT, I made concentrates at these ratios that I could dilute to a working strength SLIMT pre-bleach. When I said the SLIMT solutions are usable here, I was thinking of the concentrates I made. I don't recall if the concentrates were proposed in Kachel's paper; I vaguely recall they were.

 

[Doremus Scudder]

SLIMT stock solutions per Kachel are a 10% solution of potassium ferricyanide and a 3.3% solution of potassium bromide. These are used in equal parts when using SLIMT techniques (resulting in a 3-to-1-to-whatever volume of water ratio), but would need to be used in a 1-part-ferri-solution to 3-parts-bromide-solution (plus whatever volume of water) to get equal percentages of both ferricyanide and bromide for bleaching prints.

For localized print bleaching, I've been using an eyedropper to mix small quantities of bleach in a rather slapdash manner from my SLIMT stock solutions. Something like 3 eydropperfuls ferri solution plus 9 eydropperfuls bromide solution plus 50ml water more or less. Then I adjust the bleach to the needed strength either by diluting or adding more of the stock solutions (in a 1-to-3 ratio) as needed.

Best,

Doremus