[pure-silver] Re: KRST
----- Original Message ----- From: "Adrienne Moumin" <photowonder2010@xxxxxxxxxxx> 
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Saturday, August 18, 2007 9:23 AM
Subject: [pure-silver] Re: KRST
Wow, thanks for that elaboration & those citations, Richard. As always, I appreciate your time & thoroughness!
In trying to get a handle on all of this, and break it down to the simplest terms so I can remember it well enough to put it into practice, I looked back into my own personal archives of pure-silver posts on this topic. I think I found one which condenses it, in this excerpt from an 11/03 post (AFA I can tell) by Russ Gorman:
This looks like a quote of something I posted in the past although it may be a paraphrase. The information about using KRST at not greater than 1:9 and for not less than 3 minutes came from Dr. Douglas Nishimura, of IPI, in a private conversation although I think he posted it to the rec.photo.darkroom Usenet group and maybe even to this list. Unfortunately, none of the toners currently considered to provide full image protection will do so without causing some change to the appearance of the image. Stabilizer treatments like Sistan or Ag-Guard do not seem to be as effective as a toner although they may be useful where a print must be displayed and no change in appearance is desired. Evidently, IPI did some preliminary testing on Sistan which did not turn out well. Dr. Nishimura mentioned this to me but later said the person who did the testing had made some error in method. I think this had to do with leaving too much of he stuff in the emulsion. Sistan will cause staining unless the amount is right. The problem is that Agfa changed their recommendations a couple of times. If there is not enough Sistan in the emulsion the protection is limited, if too much the Sistan itself causes problems. Probably the safest treatment is either a Liver of Sulfur toner or strong KRST. Combination toners like the original Viradon or Kodak Polytoner also apper to provide complete protection but both are discontinued. I have a formula for a combination toner, published long ago by Kodak, which works. It has no advantage over standard toners as far as protection but can produce a modified color. I've posted the formula to this list in the past. Liver of Sulfur toners have the peculiar property of toning faster when diluted or when partially exhausted. This same property also causes them to continue toning in the wash until most of the toner is washed out. If very dilute or quite exhausted the toner can generate a peach colored stain which is difficult to remove. So, KBT should not be diluted further than indicated in its instructions. The continued toning can be stopped by treating the material in a 10% solution of Sodium Sulfite before washing. Actually, I've found that plain Kodak Hypo Clearing Agent at normal working strength works fine. This also immediatelly clears the yellow stain left by the toner. KBT is normally used at an elevated temperature because it tones very slowly. However, it works at room temperature and this may be advantageous when partially toning. My combination toner, for some reason, works very quickly, three minutes for full toning of prints. It also must have the sulfite treatment as a sort of toning stop bath and stain clearing. Ryuji Suzuki wrote me that he had staining problems with this toner but I tested using both old and new stocks of KBT and KRST and could not duplicate the problem. Copper and Iron toners, and probably other metal substitution toners like Uranium, result in images which are MORE vulnerable to atmospheric polutants than untreated silver and should be avoided where permanent images are desired. Where a blue color is desired Gold toner will produce a very permanent blue image on warm tone paper although not as vivid as Iron toner. 

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Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx

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