Lo and Behold: Turns out Black Salt Makes a Terrific Toner

Discussion in 'Alternative Processes' started by nmp, Jul 10, 2017.

  1. OP
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    nmp

    nmp Member

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    If you research "silver patina," you will find some very innovative ways of tarnishing (we call it toning) silver engaged by jewellery makers. I don't see why something won't happen to a salt print when exposed to some hard-boiled eggs. Practicality is an another matter. You can try the next time you make an egg-salad...:smile: I have tried Liver of Sulfur, another favorite of jewellery artists (which is also the basis of polysulfide toner) and so far the results have been analogous to the black salt. If you are suggesting use of bare H2S gas, synthesized somehow in-situ and exposing the print, I would be careful as it is toxic if over-exposed to - not something I would like to play around with.

    :Niranjan.
     
  2. NedL

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    Definitely not! Even if I make a "extra hard boiled egg" fumer, it will be out in the garage. I don't like to mess around with H2S at all.

    A reason I'm interested in this is that in the paper positive process we've been using, the bleach converts metallic silver to something ( probably some kind of silver citrate complex ) and leaves the undeveloped silver bromide alone. If you re-expose the paper to light and re-develop in normal print developer, the "silver citrate" areas do develop, but they are slower than the silver bromide areas. This is good and bad: the re-exposure gives additional control over the result, but it's also another "moving part" and one that's tricky ( you have to judge the right amount having only seen what the negative looks like! ) However, if you do not re-expose to light, thiourea will "develop" the unexposed silver bromide, and it leaves the "silver citrate" completely alone... so the reversal is more perfect, and it is controlled completely by the original exposure and the 1st development, making it much simpler to home in on what works well. I'm going to try kala namak, but I'd like to see it make a darker tone on an unexposed piece of photopaper before I do...

    I'm curious if there are other fogging agents that might work like this, and sulfides are prime candidates. Thiourea does not seem to produce H2S while it is "developing" the print, but some definitely is produced when the print is then washed in water, so I have to do it all outside...also I think I have detected a slight H2S odor when the print is then fixed, even after a very long wash sequence.

    Thanks for the hint about "silver patina", that could lead to other things :smile:
     
  3. RalphLambrecht

    RalphLambrecht Subscriber

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    truest words ever spoken
     
  4. OP
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    Let's see if I can understand correctly. The approach you are describing seems to be similar to the one where the sepia toner is used first and then the bleach (https://www.photrio.com/forum/threa...reversal-processing-using-sepia-toner.155754/) reversing the classic indirect sepia toning process. The difference is you are using non-halogenating bleach first to protect the positive silver image before toning. If you are using thiourea, being that it is an indirect toner, you do not need to bleach first since it will not react with the metallic silver. On the other hand If you want to use a direct toner like polysulfide, selenium or the black salt, then pre-bleaching is required as you are already doing - although I am not 100% clear on whether or not these will also react with the "silver citrate" part of the print. That would be the real test.

    Happy experimenting!

    :Niranjan.
     
  5. NedL

    NedL Subscriber

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    I think everything you wrote is correct, and the key is whether or not an alternative to thiourea will react with the "silver citrate" parts. I'm not clear at all about that part and won't even hazard a guess! :smile: I was not expecting thiourea to work so well as it does.
     
  6. RalphLambrecht

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    very interesting; I'm gonna try a 2% solution if I can find the black salt.
     
  7. OP
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    Try a South Asian grocery store if nearby or even a natural/health food store. Amazon has many brands available as well.
     
  8. RalphLambrecht

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    Yes, I found it in both.Seems to be easier than finding the poorly defined polysulphide.
     
  9. OP
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    Great...please share your experience.
     
  10. RalphLambrecht

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    I have secured 200g from the local Asian food store(powder only) and will try to use it at 2% soon.
     
  11. RalphLambrecht

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    I intend to mix it as a 2% solution and use it just like a working solution of Agfa Viradon;will report after first results.
     
  12. OP
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    should be interesting....
     
  13. OP
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    Hi, Ralph:

    Wonder if you had any luck toning silver gelatin with black salt.

    :Niranjan.
     
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  15. NedL

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  16. OP
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    Aha, I see. Missed that thread. I guess if Ralph had reported here as he said he would do, I would have known.

    In any case, I did some experiments on Centennial POP for which earlier I had developed a selenium (KRST) process to tone the orange-red color to chocolate-brown color with significant increase in Dmax, an equally important goal to pursue.

    Here is a graph depicting curves of POP Dmax (as measured with a scanner in the form of RGB value) as a function of toning time for various concentrations of black slat in comparison to the standard KRST (1:60) toning:

    BalckSalt_on_POP.jpg


    The process is fix, hypoclear, wash, 2% Na2CO3 for 5 min and then straight to toner. The black salt toners are simply black salt in dist. water prepared right before using. Earlier I had found that adding Na2CO3 in the toner itself, as it is in a typical polysulfide toner, slowed down the toning rates considerably so I decided to skip it.

    Evident on the chart, It seems that 0.5% black salt is optimum (the blue curve) for this paper. Lower (0.2%) and higher (1.0%) both were slower and and less effective than the 0.5% formulation. The only theory I have right now as to why toning slows down at higher percentage would be that there is simultaneous bleaching and toning going on in the toning bath and perhaps bleaching becomes more dominant at higher salt percentages. Incidentally, I found that 0.5% was also optimum for the salt-free salt process that I reported before. In comparison, KRST (1:60) is much faster its reaching the full toning potential in addition to giving an extra boost in the Dmax compared to the black salt toner (Mean RGB of about 25 compared to 30 or so in the latter.)


    :Niranjan.
     
    Last edited: Apr 4, 2018
  17. NedL

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    I can't remember if I already wrote this, but in my limited experiments with black salt as a re-developer, I found 0.5% worked best too. Have you tried changing the concentration of the Na2CO3 bath?
     
  18. OP
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    You mean the pre-toning treatment, right. No, I used standard 2% which is what I put in the fixer too.
     
  19. NedL

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    Not necessarily relevant to toning, but I just took two strips of unexposed photopaper, soaked one in 2% Na2CO3 and the other in 8% Na2CO3 for 5 minutes, and then put them both into 0.5% black salt. They both toned to an even tan color and I can't see any difference.
     
  20. OP
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    Good to know higher concentration does not make it worse. The only reason I put Na2CO3 in the process was to counter acidity in tap water which I thought was detrimental in the subsequent selenium toning chemistry. I am not sure if 2% is the ideal or the minimum. I suspect you can get away with lower percentage. in my earlier experiments with much more concentrated KRST (like 1:10, 20, etc) the alkali treatment seemed to help. I stuck with it even though ultimately I ended up with a much higher dilution at 1:60.

    :Niranjan.
     
  21. RalphLambrecht

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    II did and it worked great as a direct sulphide toner; at 4-8 min,I got a nice warming of the highlights without noticable after-toning in the final wash.
     
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