[pure-silver] Re: print washer
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Thu, 20 May 2010 15:10:49 -0700
----- Original Message -----
From: "John Stockdale" <j.sto@xxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Thursday, May 20, 2010 2:48 PM
Subject: [pure-silver] Re: print washer
In "Photo Techniques" a few years ago there was a two part
article called "Mysteries of the Vortex" about water flow
in washers.
It was apparently originally printed in a UK magazine.
Here are links to the two parts:
http://www.film-and-darkroom-user.org.uk/forum/showthread.php?t=296
http://www.film-and-darkroom-user.org.uk/forum/showthread.php?p=3486
Worth a read.
John
Someone sent me this article many years ago. I think it
has some faults but I just read over the conclusions from
the on-line version and don't see anything wrong. He makes
the points (as I did) that the washing takes place at the
surfaces so its important that the flow of water there be
rapid and continuous. A sulfite wash aid makes an enormous
difference in wash rate and is important in conserving
water. The HT-2 test will tell you if your washing system is
working. I think its also important to test fixing using the
sulfide or selenium test.
A note on older washing tests: a long time ago a test
using potassium permanganate was published by Kodak and
others. This test is indirect and tests for the amount of
hypo in effluent wash water. It is not an effective test
because the run-off from a print or film can show no hypo
when there is still an unacceptable amount of hypo bound to
the emulsion and silver image. It is a useless test and
should not be relied on.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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