From: Liam Lawless (liam.lawless@blueyonder.co.uk)
Date: 07/21/02-02:35:21 PM Z
Robert,
An old booklet I have here gives a chemical reversal bath for reversal
colour film/prints, instead of re-exposing to light. I think I've used it
and that it worked, but so long ago that I don't remember the details.
Formula is:
Propionic acid 15 mL
Stannous chloride 2 g
Sodium hydroxide 5 g
Water to make 1 L
The instructions are:
Instead of re-exposing colour reversal films to light, the above may be used
after the first developer in place of the first stop bath. Take care to
avoid contact with this bath and wash hands and all containers thoroughly.
Rinse the film for half a minute after the first developer. Do not use the
stop bath. Treat the film in the reversal bath for 2 minutes at 38 deg. C
and then wash for 2 minutes in running water before continuing the rest of
the process.
This will probably do the trick (maybe extend the time a little at the lower
temperatures used in B&W work?) Didn't the old E-4 process use something
else to do the same job - tetrahydrofuran or something like that, but I seem
to remember it was highly toxic. And presumably still is.
Liam
-----Original Message-----
From: Robert Schaller [mailto:Robert@RobertSchaller.net]
Sent: 21 July 2002 18:13
To: alt-photo-process-l@sask.usask.ca
Subject: fogging developer
I wonder whether anyone out there knows of a readily available agent that
will develop silver halide regardless of whether it has been exposed (a
useful way to avoid the need for reexposure in reversal development). Kodak
has used Sodium Dithionite (95% Sodium Hydrosulfite), about which I know
nothing nor where one might get it, and a Barbitol compound, but this is
hard to get, being a barbituate and hence a controlled substance (although
there is no doubt a source I am not familiar with). A low-tech solution
would be preferable. What works as a reducing agent for AgH without needing
exposure?
This archive was generated by hypermail 2.1.5 : 09/19/02-11:11:01 AM Z CST