problems with toner bleach

[NewMexican]

Hello,
I'm having trouble learning to bleach and tone.
I have tried the "standard" formula of 10mg Kbr/5 mg Pot ferri/ liter water and have found it way too quick to bleach with several papers. I have tried FOA and Ilford fbwt and after 30 seconds the image is pretty much gone. I would like more control as I have been trying to use a couple of different toners.
Can I lenghten the bleach time by using less potassium fer ferricyanide? Should I fix/wash again between bleach and toning?
thanks in advance,
charlie

 

[Rudeofus]

Yes, you can lengthen bleach time by diluting the bleach. Make sure you have enough total Ferricyanide and Bromide in your bleach, or you will exhaust them and get uneven effects. You should wash thoroughly after bleaching, but you should most definitely not fix after bleaching, or all your Silver Bromide is gone and there will be nothing left for the toner.

 

[MattKing]

One qualification to what Rudeofus just posted - if your intention is just to bleach the print (to lighten it) then you should fix after bleaching.

 

[jochen]

Hello,
the bleach bath before a sulfur toning process shall reconvert the silver completely into unsoluble silverbromide. The black silver image disappears and turns very slightly yellowish (silverbromide is yellowish). After washing out the chemicals the silverbromide reacts with the sulfide or thiocarbamide in the toning bath to brown silversulfide.
The components of the Farmer reducer are potassiumferricyanide and sodiumthiosulfate. With this bath the silver is oxidized into silverferrricyanide which is soluble in the thiosulfate. The silver which is bleached with Farmer is lost for ever.

 

[Rich Ullsmith]

For better control, mix a stock solution of 100g KBR and 100g Kferri in 1 liter of distilled water, then titrate as necessary. If you use a fresh mix at each session, you can keep notes and really fine tune you titrations for specific papers.

I prefer stronger bleach in all cases. With weaker bleach and longer slower bleaching, it will soak into the fibers and continue bleaching for a short period after it is removed. A print placed face down in a stronger bleach for only one or two seconds and removed quickly does not give time for this to happen. I know this sounds counterintuitive, but it seems to work.