Re: washing sheet film
michael gudzinowicz (ab366@osfn.rhilinet.gov)
Wed, 13 Mar 1996 21:22:31 -0500
Judy writes:
>It occurs to me that someone may have a better solution for washing sheet
>film than I do (actually, that would be easy). I suppose it could go in a
>printwasher, but the wet time would be too long.
It depends. Use two fixing baths, rinse the negatives for a few
minutes with water, then soak in hypoclear for 5 min. Rinse,
and place in a washer with water running for 10 min. Hypo
should be removed at that point. Filling/dumping the tank for
a couple of 5 min soaks will remove and dilute any residual
fixer.
>The problem is that light film rises to the top of the tray in
>one-at-a-time tray wash and unless you poke it down every minute dries on
>top. Even a cascade of water from a long pipe with holes has to be
>re-aimed every minute or so. Most difficult is the N31P 30 by 40 cm --
>does not stay under. I'm contemplating steps, but before going whole hog,
>thought I'd ask....
You could put a metal film clip on the non-image areas of
diagonally opposite corners to keep each sheet at the bottom of
its tray, and use the wash approach mentioned above to conserve
water. The rate of diffusion through the emulsion determines
the wash time - a large volume of water in the tray and gentle
agitation establishes a very low concentration at the emulsion
- water interface... constant flow doesn't speed the process
much after the initial few minutes.
After the wash, I soak negatives in the following solution for
a couple of minutes: 1 gal distilled water with 100 ml 70%
isopropanol (rubbing alcohol) and 10 ml Photoflo added.
Negatives are then hung to dry _without_ wiping, though a paper
towel can be touched to the bottom edge/corner after a few
minutes to remove a small bead of water.. They dry absolutely
spotless, and the solution can be reused.
If a fresh second fixing bath is used, all of the insoluble
argentomonothiosulfite will be removed, and the hypoclear will
facilitate the rapid removal of hypo. (There's some evidence
that residual hypo may protect against oxidizing gases.)
Considering the environment in a darkroom, I wouldn't store any
unexposed film, negatives, chromes or prints there - the risk
of damage is probably greater than that from processing error.