[pure-silver] Re: KRST Shelf Life
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Fri, 9 Sep 2005 06:27:48 -0700
----- Original Message -----
From: "Alparslan Berik" <berika@xxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Friday, September 09, 2005 5:09 AM
Subject: [pure-silver] KRST Shelf Life
Hello all,
I wonder how long Kodak Rapid Selenium Toner's shelf life
is. I remember
reading comments here it is very long. I have a bottle of
KRST and I use it
1+20 with Ilford RC .44M multi contrast paper. I used to
get beatiful deep
blacks and if left the paper more than 10 minutes in the
solution it would
get a nice toning, but not anymore. I prepared a fresh
working solution, and
the result is the same. It seems KRST effect has
diminished in time. This
happened to my working solution before but I had vever
thought that this
would happen to the stock KRST.
I think I bought the bottle 2-3 years ago. Is it normal
for such a long
time. Should I dump the rest of the bottle. Thank you for
the comments.
Alparslan.
If you mean the concentrate the shelf life is very long,
even after opening it. I have some KRST that is at least 10
years old and works as well as some I bought a couple of
months ago.
The main problem for high dilutions is being diluted in
Kodak Hypo Clearing Agent. This was a Kodak recommendation
for a long time, the idea being that the mixture would
perform both functions, i.e., toning and washing
acceleration, in one step. Additionally, the KHCA acts as a
slightly alkaline envrionment for the toner preventing a
type of staining that can happen when acid is introduced to
the toner. The problem is that the sulfite in the KHCA
oxidizes to sulfate fairly soon. As Sulfate really does no
harm and continues to be slightly alkaline, but it no longer
is very effective as a wash aid. The other problem with
using high dilutions, i.e., 1:19 or more, is that the
capacity of the bath is limited regardless of what it is
diluted with. However a high dilution of KRST in water or in
a mild alkali is sill an effective toner after considerable
time.
BTW, both my old and the brand new KRST had a little
precipitate in the form of black particles in the bottom of
the bottle. All the bottles at Freestyle had the same
precipitate. This forms when diluted toner is stored for a
time and evidently has little or no effect on toning
ability.
The test for the toner is whether it tones. If its
functions its OK.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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