[pure-silver] Re: Weird Film Issue - Part II
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Wed, 9 May 2012 00:08:56 -0700
----- Original Message -----
From: "Howard Efner" <hfefner@xxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Tuesday, May 08, 2012 2:32 PM
Subject: [pure-silver] Re: Weird Film Issue - Part II
The addition of something like 1 oz rubbing alcohol (70 or
90 percent isopropyl alcohol, nothing else added!) per L
of water, will also reduce surface tension and will be a
solvent for photo-flo residue.
Howard
This was my suggestion. The combination of isopropyl
alcohol and Photo-Flo makes a kind of super-wetting-agent.
The amount is not critical, about 35 ml (an ounce or a bit
more) of 70% isopropanol to a liter of water to which ad
one-half capful of Photo-Flo (about 2.5ml). This is half the
recommended amount. While distilled water may help plain tap
water is satisfactory unless the alkali level is very high
or it is very dirty. Boiling the water for a few minutes
and letting it cool will remove much temporary hardness.
Temporary hardness is mostly magnesium or calcium
carbonates. This is probably the material that is leaving
deposits on film.
"Drying marks", are caused by beads of water which form
on the surface of the emulsion and cause localized swelling.
Sometimes there is some migration of the silver due to the
difference in emulsion hardness, this leaves dark marks
around the drying marks. Drying marks can usually be seen
by light reflected from the surface of the film. Sometimes
they can be removed by soaking the film for a few minutes,
treating it in a wetting agent as above, and re-drying but
sometimes no treatment will remove them.
I do not like to squeegee film because it is very
likely to cause scratching or gouging. If a proper wetting
agent is used there is no need to squeegee because the water
will run off the film rapidly and not bead up.
Mineral deposits on film can often be removed by
soaking in an ordinary acetic acid stop bath for a few
minutes, then swabbing gently with cotton swabs. After this
the film should be washed for a few minutes and treated with
the wetting agent before drying.
--
Richard Knoppow
Los Angeles
WB6KBL
dickburk@xxxxxxxxxxxxx
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