The user at APUG who advocates 1:19 fixer single shot is an idiosyncratic fellow and his system has very little support. I can remember Ryuji Suzuki saying that it runs the risk of inadequate fixing.
Se toner contains lots of thiosulphate. It is not necessary to remove fixer (thiosulphate) before Se toning, BUT it is very important to remove acid from the paper before SE toning. Since most fixers are acidic to varying degrees, this is the reason that rinsing between fixing and Se toning is advocated. Alternatively, alkaline fixer can be used, or an alkali bath after fixing can remove the acid before the Se toning stage.
John Stockdale ==================== Tom Kershaw wrote:
Richard,On Thursday I processed several full sheets (with no exposure, aside from a '902' type ILFORD safelight) of different paper varieties through developer, stop, and a two bath fix, both diluted @ 1:9; then washed for 45 minutes in a Nova printwasher without an HCA stage. My intention being to test for both residual silver and residual fixer (with the standard test) over the full sheet.The use of selenium toner as a test for residual silver does bring into question what kind of processing regime one should use if selenium toning is included. Should one try and get all residual fixer out of the paper before toning in KRST or any other Se toner, which to my knowledge all contain Ammonium Thiosulphate and will therefore introduce additional compounds that need to be washed out of the paper; or is a 15 minute wash between the 2nd fix bath and the Se toner, and then washing for the full time (e.g. 45 minutes, depending on testing) more likely to prove an efficient and effective washing regime?Out of interest, what is your view on the more recent practice of using a two bath fix regime with both baths diluted at 1:4, processing for 1 minute in each bath? - Aside from increased sales for the manufacturer (ILFORD HYPAM in my case), I'd have thought one would start to get into issues with excessive silver concentration in the fixer for fibre base processing, while at the same time possibly throwing out solutions with remaining high activity. One user on APUG advocates a single 1:19 dilution fixer for fibre base printing used fresh and one-shot but this doesn't seem a very time efficient technique if making a large number of prints.Tom On 09/07/2010 17:54, Richard Knoppow wrote:----- Original Message ----- From: "Tom Kershaw" <tom@xxxxxxxxxxxxxx> To: <pure-silver@xxxxxxxxxxxxx> Sent: Friday, July 09, 2010 6:56 AMSubject: [pure-silver] Using a selenium toner solution to test for residual silverFrom previous reading I understand that a dilute 10% solution of Kodak Rapid Selenium Toner was recommended at one point to test for residual silver on fibre base photographic paper via placing drops onto the print surface (checking for colour change) as an alternative to a sulphide solution. Any thoughts on current knowledge with regard to the effectiveness of this test?Kodak recommended a 1:9 dilution of KRST at one time as an alternative to the sulfide test. This is for _all_ materials, not just fiber paper. The test solution is used in exactly the same way as the sulfide test. The advantages are that the shelf life is longer than the sulfide and it does not have the rotten egg odor (hydrogen sulfide gas). However, the test will fail if there is an excess of hypo in the emulsion so it must be used on well washed materials only. I don't think there was any other problem but the suggestion disappeared from Kodak literature after a while. I remember seeing somewhere that the color of the stains from the KRST test actually matched the colors on the Kodak Hypo Estimator strips better than the sulfide test but I can't find that article. In any case I think the test is still a valid way to check for completeness of fixing. Note that either test will eventually cause a stain if not washed out. For that reason its best to make a test on a scrap of film or paper that has been gone through the usual process. The rate of fixing depends on whether the emulsion is wetted before it goes in the fixer to material used to test a fixing bath should be soaked in water for a few minutes before being fixed. Kodak ran afoul of this when making early tests on the effect of hypo concentration on fixing time. Their early published results showed a peak in hypo effectiveness at a certain concentration and slower fixing with stronger solutions. It was discovered later that this was an artifact of using dry emulsion and when wetted emulsion was used there was no such peak and fixing time continued to become shorter as fixer concentration was increased.Tom Kershaw-- Richard Knoppow Los Angeles, CA, USA dickburk@xxxxxxxxxxxxx============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.
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