[pure-silver] Re: Problems with KRST????

  • From: Richard Knoppow <dickburk@xxxxxxxxxxxxx>
  • To: pure-silver@xxxxxxxxxxxxx
  • Date: Sat, 5 Apr 2008 05:32:48 -0700 (GMT-07:00)

-----Original Message-----
>From: Bogdan Karasek <bkarasek@xxxxxxxxxxxx>
>Sent: Apr 4, 2008 8:50 PM
>To: pure-silver@xxxxxxxxxxxxx
>Subject: [pure-silver] Re: Problems with KRST????
>Hi Richard,
>I'll try the different paper route, Ilford Fiber and Agfa MultiClassic 
>but I find it strange that the previous poster has been using Kentmere 
>with no ill effect, except that I don't know what KBT stands for ;)
    KBT = Kodak Brown Toner. KBT is a polysulfide toner similar to Kodak T-8 
and to "new" Viradon. It is a concentrated solution of Liver of Sulphur. KBT 
has the advantage that it tones all densities uniformly (no split toning) so it 
useful for image protection where minimum change in color or density is 
desired. A version of this type of toner is currently recommended by the Image 
Permanence Institute for use on microfilm instead of diluted KRST. IPI 
published its own formula to avoid the problem encountered with KRST which 
evidently changed somehow during its manufacturing lifetime. However KBT works 
fine for this. KBT is a direct toner like KRST, that is the print or film is 
immersed in it with no previous bleaching step. It is recommended that a 10% 
solution of sodium sulfite be used immediately following toning to stop the 
toning process and to clear any yellow stain. I've found that normal working 
solution of Kodak wash aid works fine even though its only about 2% sulfite. 
Polysulfide toners have the peculiar property of toning faster as they become 
exhausted or more diluted so, unless the sulfite bath is used, the toned prints 
or film will continue toning in the wash bath until a substantial amount of the 
toner is removed. If not washed out quickly enough the toner can leave a peach 
colored stain. I have not found this to be a problem in practice. Like any 
toner KBT will work better for some papers than for others. Like KRST it will 
protect the image of any paper or film even when it makes little difference in 
image color but if one desires a color change the performance must be 
determined by experiment. 
     As a general rule (but with exceptions) toners are more effective on warm 
tone paper than cold. This is partly due to the grain size but can be affected 
by other things such as the balance of chloride and bromide in the paper. 
Toners are also affected by the developer so one must try the combination to 
find out how it looks. 

Richard Knoppow
Los Angeles, CA, USA
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