[pure-silver] Re: Hypo Eliminator
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Thu, 17 Feb 2005 23:02:43 -0800
----- Original Message -----
From: "Ryuji Suzuki" <rs@xxxxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Thursday, February 17, 2005 9:41 PM
Subject: [pure-silver] Re: Hypo Eliminator
> From: Peter De Smidt <pdesmidt@xxxxxxx>
> Subject: [pure-silver] Hypo Eliminator
> Date: Thu, 17 Feb 2005 23:29:44 -0600
>
>> Question 1: would hypo eliminator counteract the tendancy
>> of KBT to
>> stain prints? (If not, the next question is pre-empted.)
>
> I doubt it. (As long as KBT is fresh, it seems to stain
> only specific
> papers but I don't know how to prevent it.)
>
>> Question 2: Is there any reason to not use hypo
>> eliminator to
>> minimise wet time? Last night I was up to 4 am finishing
>> processing
>> prints, and I'd appreciate any way to cut down the
>> processing time.
>
> Hypo eliminator is discouraged because it oxidizes some
> image forming
> silver to a form that is more susceptible to fading. The
> harm from
> this after toning should be very small, as long as toning
> protection
> is adequate. But the susceptible form is invisible so you
> won't know.
> Chloroacetate is said to react with thiosulfate without
> oxidizing
> silver but I haven't looked further.
>
> --
> Ryuji Suzuki
> "Keep a good head and always carry a light camera."
>
Kodak was evidently aware of this problem and suggested
that Potassium bromide be added to the eliminator to prevent
the color change to the image. There are other problems with
hypo eliminator so it has not been recommended for a couple
of decades. A sulfite wash aid is quite sufficient.
Staining from KBT _may_ be from unfixed halide but it
also can cause a stain if its not stopped with a 10% sulfite
bath after toning and before washing. Polysulfide toners
have the peculiar property of toning faster as they become
diluted or exhausted. When you put a toned print in the wash
it will continue to tone at an accelerated rate until the
toner is washed out. Washing must be very rapid at the
beginning. A "stop" bath of 10% sodium sulfite (about stock
KHCA) will prevent the continued toning and staining. The
print must be treated in this for a couple of minutes before
washing. I don't know the chemical basis of this but it
seems to happen.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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