From: Bob Kiss (bobkiss@caribsurf.com)
Date: 01/26/02-08:57:16 AM Z
DEAR SANDY AND JUDY,
I think there may be some confusion between Hypo-Eliminator and Hypo
Clearing agent.
The old Hypo Eliminators, made by both Kodak and Heico contained ammonia
and hydrogen peroxide. Some researchers said that they eliminated TOO MUCH
sulfur (usually in the form of Silver thoisulfate complexes) and minute
trace amounts of sulfur were actually better for image permanence. They
also said that residual ammonium peroxide may be left in the image which
also might be bad for print longevity.
Hypo clearing agent contains, among other things, Sodium sulfite, EDTA,
and Sodium meta borate, all pretty benign stuff that gets the
sliver-thiosulfate complexes out via both a replacement reaction (leaving
behind the trace amounts of "good" sulfur) and by moving the ph of the
gelatin zwitter ion (has a basic ion at one end of the molecule and an
acidic ion at the other) to the right point to release (unbond) unwanted
ions from either end of the molecule. At least this is what I was taught
by dear ol' Dr. T. H. James. It is a decent first approximation to a much
more complex process.
Soooooooo, Hypo eliminators have a bad rep and hypo clearing agents a
good one.
CHEERS!
BOB KISS
----- Original Message -----
From: Sandy King <sanking@clemson.edu>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, January 25, 2002 9:37 PM
Subject: Re: Kallitype vs. PT/PD
> Judy Seigel wrote:
> >
> >
> >
> >I think palladium costs as much as platinum now, doesn't it, or is that
> >just rumor?
>
>
> I only use the platinum #3 solution for toning, which I think is a
> mixture of palladium and platinum. It is fairly expensive.
>
>
> >
> >But I wonder about your mention of hypo eliminator. Last I heard (long
> >ago, admittedly) experts said don't use that, bad for SG prints. Is that
> >now inoperative?
>
>
> What I use is a 3% sodium sulfite solution, followed by a wash of
> about 15 minutes.The sodium sulfite does not eliminate the hypo but
> converts it into something that does not react with the silver. Or at
> least that is what I read somewhere by someone who should know and
> that is why I use it. I understand that Kodak Hypo Clear is of
> similar composition?
>
> Sandy
>
> --
>
This archive was generated by hypermail 2b30 : 02/15/02-11:47:41 AM Z CST