SilverLock questions

Discussion in 'B&W: Film, Paper, Chemistry' started by Paul Verizzo, Mar 11, 2008.

  1. Paul Verizzo

    Paul Verizzo Member

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    Does anyone have dilution/time information on using the SilverLock preservative formula? I did get the latter off of the net, but lack instructions.

    Solid Liver of Sulfur 495.0 grams
    Deionized water to 1.0 liter
    When mixed add Borax 20.0 grams

    What dilutions, what times? Anyone have info?

    (The quick version for those not knowing: The Image Permanence Institute (??), Rochester found out some years ago that gold and selenium toning weren't all that they were cracked up to be. Selenium toning was insufficient in light areas, and in gold toner, it was the thiourea that did the heavy lifting! After a zillion dollars of experimentation, they found out that Kodak Polysulphide toner was the best bet! They modified the alkali to Borax and called it SilverLock. Having passed on the secrets to some university, they no longer even have any reference to SilverLock on their site.}
     
  2. tim rudman

    tim rudman Member

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    Hmm. This is not an easy project for a home darkroom. I don't know what facilities you have but perhaps this extract from my Toning book will put you off :smile:

    "IPI toner ‘Silverlock’

    The Image Permanence Institute produced their own polysulphide archival toning product ‘Silverlock’. Although this was designed for microfilm, it has been tested and found to be highly effective for other types of film too. For a while this was available as a kit. Production however is difficult, expensive and time consuming. Liver of sulphur (a.k.a. ‘sulphurated potash’ and potassium polysulphide) has no specific formulation and does not come in reagent grade form. There is considerable inconsistency from batch to batch and production of a consistent end product is therefore difficult (note how the colour of Kodak Brown Toner varies from batch to batch for example). As a result of all these factors IPI no longer make Silverlock.

    For academic interest to the ‘make-up artists’ amongst you, I share an abbreviated description of the production details, which, as you will see, come firmly under the category of ‘don’t try this at home’! I am indebted to Dr. Douglas Nishimura at IPI for generously sharing his time and experience with me on this subject.

    10kg of liver of sulphur are dissolved in 20 litres of water (or pro rata!)
    Original batches of Silverlock were made using borax. Subsequent supplies of liver of sulphur were so different, that in order to lower the pH to the desired point, this was changed to citric acid, which was added at 600gm in a litre of water until the pH fell to 11.4. Large amounts of hydrogen sulphide are released and this absolutely must be done in a fume cupboard. The rate of addition (very slow) and constant stirring are essential factors. The resulting solution is left overnight, to allow elemental sulphur and impurities to settle out, and then is evaluated against the original borax formula. Concentration and acidity are adjusted, the solution left again to settle and re-testing undertaken until the correct balance is achieved.
    Not a job for the home darkroom!"

    Still want to make it at home? :smile:
    Tim
     
  3. Paul Verizzo

    Paul Verizzo Member

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    Still want to make it at home? :smile:
    Tim

    Sure! Well, maybe not tonight. :rolleyes:

    In my research I've come to realize that Liver of Sulfur is a whole lot of possibilities of chemical makeup and misnomers.

    But underlying all of the quality control is the fact that even plain vanilla Kodak T-8 works well as a preserver of images.

    I'm a big believer in "Good enough." There is a time and a place for perfection, and probably university and cinema preservations are good places for perfection. OTOH.....

    However, I am shocked at seeing that Liver of Sulphur in water apparently has a pH near sodium hydroxide? Or what am I forgetting or overseeing?

    "Subsequent supplies of liver of sulphur were so different, that in order to lower the pH to the desired point, this was changed to citric acid, which was added at 600gm in a litre of water until the pH fell to 11.4."


    As if a bit of borax would influence such alkalinity? How about T-8 and its addition of sodium carbonate.

    OK, I admit it, I'm confused.

    Regardless, thanks for the great and informative reply.
     
  4. Paul Verizzo

    Paul Verizzo Member

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    Oh yeah, Tim...

    Dilutions and times?
     
  5. Olli J

    Olli J Member

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    I use it in dilution 1:20 to 1:50. The dilution and time very much depends on what you are after. If you just want to enhance the arhivality of your prints or negs, then treatment with 1:40 for 2-3 minutes should be enough. If you also want a hue shift, then start with dilution 1:20 and test. Papers react differently. Warm tone papers may show hue shift after a minute whereas some neutral tone papers like Ilford MGIV cools down a bit and gains some density but nothing else in several minutes. I recommend to tests your papers. Remember to use 10% Na-sulfite "stopbath" unless you want the hue shift to continue in the wash.
     
  6. Paul Verizzo

    Paul Verizzo Member

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    Gracias!

    Thanks, Olli.
     
  7. snallan

    snallan Member

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    The thing to keep in mind, is that Liver of Sulphur is not a chemical compound, but a poorly characterised mixture of polysulphides of potassium, and also includes potassium thiosulphate. The only specification being that it contains not less than 12.8% of the sulphur as sulphide (Merck Index, Eleventh Edition (1989)). The pH of a solution will therefore vary widely, depending upon the overall composition of the Liver of Sulphur.

    As for attempting to make it yourself. Really only try this if you have access to proper laboratory facilities, as it will liberate lethal volumes of Hydrogen Sulphide.
     
  8. tim rudman

    tim rudman Member

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    Polysulphide toners are used highly diluted Paul.
    Kodak recommend for Brown Toner a dilution of around 1+30 (30ml in 946ml water) for 15-20 minutes at 68F/20C but this is reduced to around 3 to 4 minutes at 100F/38C with continuous agitation.

    Polysulphide toners work fairly uniformly though the tonal range (unlike selenium or gold) and they also have the rather unusual property of working faster when they are more diluted or partially exhausted. Their action tends to accelerate initially in the wash therefore, and this can lead to a permanent peach coloured stain in the highlights.
    A ‘toner stop bath’ of strong hypo-clearing agent, followed by an initially vigorous wash or hose down, will minimise this. Agfa recommends a post-toning bath of sodium sulphite, which of course is the main ingredient of hypo-clearing agent.
    Kodak also recommends an after-treatment with Kodak liquid hardener.

    Brown toner or Agfa Viradon New and a lot simpler to use than home brew Silverlock. :smile:
    Tim
     
  9. Paul Verizzo

    Paul Verizzo Member

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    Yeah, I've pretty well figured that out...

    I guess we haven't left alchemy that far behind........

    I'm tempted to quip that I used to have to drink "sulfur water" here in Florida as a kid, so I know how "lethal" it is. But thanks for the extra warning.

    The city water here is much improved of forty years ago. But it's still there, just a tad. Thank God for charcoal filtration!

    So, all, if liver of sulphur is so variable, what's wrong with Pot. polysulfide or sulfide? For image protection, is there something magic about the many different molecule lengths of "liver?"

    The liver is pretty expensive, too. The cheapest I found was about $30 a pound inc. shipping.
     
  10. dancqu

    dancqu Member

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    The IPI and Sodium Sulfide

    Included in the IPI's research was the effect
    on LE with the use of a very dilute solution of
    sodium sulfide. A dilution of 1:9,999 was found
    to be completely effective in imparting a
    very great LE. Dan
     
  11. dancqu

    dancqu Member

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    The polysulfide is essentially a sulfide with
    excess sulfur attached; sulfide Na2S, poly
    Na2S2, 3, 4, 5. Sulfur dissolves in any
    soluble sulfide.

    T-8 IS a polysulfide toner. Likely it has the
    characteristics of a one-size-fits all formula
    and is suitable for tinkering.

    Read that IPI report one more time. According
    to them Sodium sulfide VERY dilute will do the
    job. In mind were large scale commercial
    applications using the poly.

    All that having microfilm and microfiche
    in mind. Dan