Selenium Toning and Bleaching Steps

If your are doing spot bleaching, or general reduction bleach and then fix before selenium toning. PF works on the silver. Once selenium toned there is no silver to work on.
But I would ask why? You would generally you would use work prints to get the image your want then tone a finished print.

TR

 

IIRC Ansel Adams used to mix his selenium toner with hypo clear. He explained why in his book "The Print". However I have found that wash, tone, wash aid, wash always worked for me. Not that I claim to know better than AA though.

 

No need to mix Selenium toner with Hypo clear, it works fine without, but after toning using a hypo clear is very useful with Fibre based prints.

Ian

 

I seem to recall reading somewhere that Bruce Barnbaum mixes his selenium toner with water for the simple reason that the toner has a greater capacity than the hypo clear; and on that basis mixing the selenium with hypo clear was a waste of useful, expensive toner.

I've always just mixed the toner with water and hypo cleared after the toning. I think a good wash before toning is important, however, to avoid staining.

 

If you are bleaching for reduction or spotting, do so before toning for the reasons mentioned above.

If you are keen to experiment with image tone, try bleaching after selenium toning to accentuate the brown/purple tone. Fix afterwards.

 

Can you point me to a Kodak reference for this? KRST is approximately 60% ammonium thiosulfate IIRC. Why you would mix HCA/sodium sulfite with what is essentially Rapid Fixer is beyond me. I would think mixing them together would kill the activity of both or at least shorten the shelf life.

I always use HCA after KRST to get rid of the thiosulfate.

 

He's right, have a looking at the Kodak MSDS for KRST - it's clear that it contains 27% Ammonium Thiosulphate in the concentrate along with 10-15% Sodium Sulphite.

Kodak Rapid Selenium Toner
Weight % Components

55 - 60% Water
27% Ammonium thiosulphate
10 - 15% Sodium sulphite
2% Selenious acid, disodium salt (Sodium Selenite)

So the amount of Ammonium Thiosulphate is actually roughly 60% or more of the weight of chemicals neede to make up the formula yourself.

Ian

 

So is the sulfite/HCA a buffer or oxygen source? What's it doing in there?

 

Never really thought about it, but as the selenium toning progresses the selenium is replacing some of the silver in the image so silver salts are formed, if these were left in the image they'd stain it, or decompose back to silver over time. So the toner incorporates a weak rapid fixer to remove these salts.

Ian

 

So is the suphite there to make it alkaline? Kind of doesn't make sense to mix it with HCA when HCA is just 2% sodium sulphite, at least my home brew is. It also raises the question of why, if you do mix the KRST with HCA, the HCA is exhausted before the toner. Very interesting...

 

That was Barnbaum's point - there is no point in mixing the toner with HCA. It wastes expensive toner.

Bob H

 

Hi Bob,
yes but HCA is basically just sodium sulphite. And now it seems KRST has quite a lot of sodium sulphite in it, before anyone mixes it with HCA. So why the sulphite in KRST and why would adding more of it make any difference to its keeping qualities?

One possibility is that commercial HCA has other things in it that will go off quite quickly but I'm still intrigued.

 

Hi Matt:

I seem to recall that the purpose of HCA was to convert the insoluble complex thiosulphate, (ite??) ions into soluble ones that more easily washed out. Could it be that the 'HCA" in the toner inhibits the formation of the insoluble ions from the thio. contained in the toner itself. I'm not a chemist, (as you can no doubt tell) but, if that were the case then mixing fixer with an HCA solution might be a good thing. Or would i just bugger up the whole process

Bob H

 

It could be but, like you I have no idea if that's true. I'm still hoping someone might chime in a definitive answer but this is a long way off topic now.

 

May be or may be not

It doesn't do to over-wash FB - removes too much Hypo (a trace of Hypo is good for long term stability) & leaches out the optical brightener.

Can you do a Residual Hypo test to check the effectiveness of your wash process?

If not and you are Toning for maximum print permanence then try pre-soaking half the batch in a bath of water for 10 mins, then a HCA bath for 10 mins & finally a 30 min wash - if they look OK when the come, out do the other half.

You would have been better rinsing the prints straight after the Toning Bath, then into a HCA bath for 10 mins and finally a 30 to 60 min wash.

Martin