[pure-silver] Re: tmx 3200 problem
- From: Richard Knoppow <dickburk@xxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Tue, 29 Dec 2009 23:53:48 -0800 (GMT-08:00)
-----Original Message-----
>From: "Ralph W. Lambrecht" <info@xxxxxxxxxxxxxxxx>
>Sent: Dec 29, 2009 10:05 PM
>To: pure-silver@xxxxxxxxxxxxx
>Subject: [pure-silver] Re: tmx 3200 problem
>
>Richard
>What exactly is dichroic fog?
>
A deposit of very finely devided silver on the surface of the film. Its
called dichroic because its yellow by transmitted light and blue or rainbow
colored by reflected light. Dichroic fog can be caused by excessive silver in
developers or fixing baths. While its usually pretty uniform it can form
blotches of the sort visible on these negatives. If this is dichroic fog
looking at it by reflected light will show it up in some color. I am grasping
at straws here but its worth a look.
I've had blotches like this on some very old Plus-X sheet film. That stuff
was jelly like and wiped off while the film was wet. I have not encountered
with with other film, just this one box.
Dichroic fog can be removed using a bleach made of acid rapid fixer at
film strength to which is added about 15grams per liter of citric acid. This
forms a mild silver bleach. Because the dichroic fog is made of such fine
particles it will dissolve before the image but the bleach needs to be used
with care because it _can_ and will reduced the image if used for too long.
It is also possible that this is a manufacturing defect. Have you any
other film from the same lot number? If its not dichroic fog I would check
with Kodak.
--
Richard Knoppow
dickburk@xxxxxxxxxxxxx
Los Angeles, CA, USA
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