Bromide drag & diahorrea toner

dogzbum

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OK, I really mean thiourea or thiocarbamide but it ends up the same colour.

I've recently taken a liking to toning prints with thiourea toning solution. The prints are bleached to completion using diluted C-41 bleach then put into the thiourea toner for about 1 minute. (Can't remember the exact formula but think it was from jackspc site).

I've noticed large areas with high density lows tend to suffer from bromide drag which I assume is a result of too much agitation or too strong a toner solution.

Which of these (agitation or concentration) should I reduce first and why?
 

Ian Grant

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C41 bleach maybe your problem. Its not designed for your application. You specifically need a Re-Halogenating bleach.

The salts used in the bleach bath can make a difference to the final tones, Sodium Chloride gives warmer and lighter tones than Potassium bromide.

The toning is to finality so your problem is highly unlikely to with this.

Ian
 
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dogzbum

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Ian, thanks, I didn't even consider the bleach may be unsuitable as it seems to work fine with sulphide based and blue toners. It has a strong dark green colour so I would assume it is dichromate based (which led me to believe it would rehalogenate).

Perhaps I will try a different bleach. I don't really want to give up on the C-41 bleach though as it is easy to prepare and cheap (I was given a 5L bottle).
 

Ian Grant

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C41 bleaches are EDTA based.

The only toner to use a dichromate bleach is Ilford IT-8, the dichromate stain and the Pyrocatechin re-developer give wonderful olive brown tones. The dichromate bleach is also used for chromium intensification of films.

The streaking with the C41 bleach is almost certainly due to the agitation and exhaustion of Bromide in the bleach. Once you've finished it up try a basic Potassium Ferricyanide/Potassium Bromide bleach they are very cheap to make up.

Ian
 

Sparky

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I'm doing the same thing - but using a copper sulfate toner. I've actually been VERY surprised at just HOW much difference the bleach appears to make in the process...! I use the copper sulfate with Sulfuric Acid and NaCl. It'd be cool to hear what your observations are. One of the more odd things I'VE noticed is that, when using exhausted bleach - the thiox bath will APPEAR to do it's thing - almost as much as usual... but I totally lose the toning on drydown and I get something much closer to a plain old silver print.
 

Ian Grant

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Sparky, the use of chloride or bromide in the bleach does make a significant difference to final image tone/colour. It is worth experimenting with different bleaches to see how they tone. Cut a scrap print into strips for the different tests, its far easier to make comparisons this way.

Exhausted bleach wont form the silver halide properly, which is iimportant in the toning process.
 

Sparky

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Yes - I think I was saying that Ian - that's why I settled on the chloride. though what seemed ODD to me was simply that the initial action was nearly identical - that the change between them happened during dry-down... (!!)
 
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