Home-brew Au toner question (or two)

Discussion in 'B&W: Film, Paper, Chemistry' started by Rich Ullsmith, Sep 24, 2007.

  1. Rich Ullsmith

    Rich Ullsmith Member

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    I did a cursory search on this, but didn't quite find what I was after.

    I've been hoarding 5g of gold chloride for some time, and now I have some prints I'm working up. I plan on using the T6 formula, which is with the potassium thiocyanate. However, one recipe calls for adding the thiocyanate solution to the gold chloride solution, and another source has it reversed. I assume chems are mixed in the order listed, but these are opposite instructions. If it makes a difference, which is correct?

    Additionally, I read a recent post concerning the shelf-life of gold toners. I have to mix enough to tone 16X20's, but I doubt I have enough prints to completely exhaust the amount of toner I need to mix. I actually pulled out the periodic table and my old chem texts to study this a little bit. It looks like a pretty stable solution, from what I can tell, then I read here that it can be expected to last for a day or so before it. . . what? Oxidizes? That is not what the chemistry suggests, but what do I know? Well, I know this stuff is expensive!

    Any enlightenment on these topics would be a big, big help.
     
  2. psvensson

    psvensson Member

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    I'm not sure which formula you're referring to - the T-6 toner in The Darkroom Cookbook contains thiocarbamide and sulfuric acid rather than thiocyanate.

    However, I've used a toner I make from ammonium thiocyanate and gold chloride quite a bit, so I can probably help you. What you need to do is make a thiocyanate solution at around 50-100 g/l (the more you use, the faster the toner works), then add gold chloride (I use a 1 percent solution) commensurate to the area of paper you need to tone. Start with 0.2 g or so of gold chloride - that should tone at least one 16x20. Then, if you find the toner starting to lose strength, add more gold chloride.

    If you want to save on thiocyanate, heat the toner to 40C or so - this speeds up toning a lot.

    Regarding the keeping qualities, I've found the thiocyanate stays active at least a couple of days, but you'll probably need to add more gold before each toning session.
     
  3. OP
    Rich Ullsmith

    Rich Ullsmith Member

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    Ah, it's the Dupont 6T formula from unblinking eye, but I think the cookbook has the same. On unblinkingeye: 750ml H20; 1g AuCl; 6g potassium thiocyanate; H20 to a liter.

    But what you are doing is adding the gold choride as necessary to the existing solution, in the amount you need. It just seems like I read somewhere that the order of mixture is important, but obviously what you are doing works.

    Is it advisable to just add the gold chloride as necessary during the session? I would prefer to do it this way. The one and only time I've done this, I mixed it per instructions and the first few prints gobbled the stuff up quick, and then fell off rapidly. Some got too much, some not enough.
     
  4. psvensson

    psvensson Member

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    I've tried Dupont 6T and found it much too slow. Or at least it is with ammonium thiocyanate instead of potassium. This could also depend on the paper - I use RC.

    I don't mete out the gold during the session for print-to-print consistency - it's more a matter of economy, in that I don't want to add too much of the pricy gold. But I suppose it helps consistency, and it's convenient and saves you on thiocyanate - the potassium salt is quite expensive, I see.

    The best thing for print-to-print consistency is toning to completion, and that requires, in my experience, a strong solution, elevated temperature, a little agitation and about 10 minutes in the bath.
     
  5. OP
    Rich Ullsmith

    Rich Ullsmith Member

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    Thanks much. I'm going to give it a go this weekend once I get things organized.

    The last recipe I used called for 1g AuCl and 105g of ammonium thiocyanate per liter, and the first few prints were kaboom! I mean instantly. After that, things slowed down. I did not get near the reported yeild from the volume of toner, although there may have been contamination issues. Not this time!
     
  6. psvensson

    psvensson Member

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    That's interesting. What paper and developer are you using? I've tried Ilford WT, Forte PWT, Agfa MC and Kentmere VC Select. I especially like the look on Ilford WT: relatively strong blue image on a pinkish base. Very intriguing.
     
  7. Jim Noel

    Jim Noel Member

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    I use CLerc's Thiocyanate/Gold Toner. I keep the two solutions in separate glass bottles until I am ready to use them. Kept this way I have never had a solution go bad.
     
  8. psvensson

    psvensson Member

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    What's the formula? The only Cleric toner I can find is for alt prints.

    http://www.unblinkingeye.com/Articles/Vandyke/vandyke.html