[pure-silver] Re: PSE CONFIRM KRST
----- Original Message ----- From: "BOB KISS" <bobkiss@xxxxxxxxxxxxx> 
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Friday, August 31, 2007 10:09 AM
Subject: [pure-silver] PSE CONFIRM KRST



For Richard Knoppow,
I have heard many different opinions recently and, though you and have disagreed, I have always respected that your postings have been 
solidly based on documented facts.
Soooooooooo, I am asking you to confirm the proper methods for toning fiber based silver gelatin prints with KRST. Since my first reading of the Ansel Adams books and as late as the 2006 G-23 document from Kodak, it has been said that one should proceed from the second fix of a two fix process DIRECTLY into a KRST toning bath comprising working strength Kodak Hypo Clearing Agent and KRST, mixed to one's preferred dilution. (I am not asking here about the proper dilution as that has been covered extensively recently) They go so far as to say that one should NOT rinse or wash 
between 2nd fix and KHCA/KRST bath as stains may result.
Please confirm that it is correct to go directly from the 2nd fix into the KHCA/KRST solution and that this will not produce yellow stains later. 

           Thanks in advance.

                       CHEERS!

                                   BOB
This method was recommended for a time by Kodak for very diluted (1:19) KRST. While KRST will often not cause stains from excessive hypo it does not like acid. The acid tends to cause a deposit of elemental Selenium on the print or film causing a very hard to remove stain. The hypo does not affect the toner much if there is a lot of it, the toner contains a lot of Ammonium Thiosulfate to start with. However, lesser amounts of hypo may cause problems. Another problem is that diluted Kodak wash aid has a very short tray life, a matter of hours. If stored for very long the sulfite becomes sulfate. While sulfate does no harm it is not a very effective wash aid. The Kodak idea was that the capacity of the diluted toner would be little enough so that the combined solution would exhaust both components at about the same time and would be tossed. Its a better practice, and evidently a necessary one if a stonger solution of KRST is used, to mix the KRST separately and use a bath of Kodak Hypo Clearing Agent or other alkaline bath before toning. It also seems better to wash the prints first after a wash aid treatment, then tone then wash again. While the toner is not acid and does not cause binding of the hypo in it a second wash aid treatment will still accelerate washing. According to Doug Nishimura, of IPI, KRST will provide complete protection to prints if used in a concentration no weaker than 1:9 and for not less than three minutes. The disadvantage of this over the old 1:19 recommendation is that it will cause a noticable change in image color or density on most emulsions. The use of KRST rather than KBT may produce a more desirable color on some materials or for some subjects. Its a matter of taste and experience. KBT is better where only protection is required because it tones all densities at the same rate so is more suitable where light toning is desired. A combination toner probably yields as good protection as KBT but I've not seen any formal testing of this. FWIW the Silver Selenide produced by KRST is just as stable as the Silver Sulfide produced by KBT, the difference in practice is due to the split toning effect of KRST. If toned far enough any Selenium or Sulfiding toner produces quite premanent images which have substantial resisitance to oxidation or further sulfiding. 

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx


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