Re:film washing

Paul and Judith Simon (70760.1511@compuserve.com)
15 Mar 96 21:50:28 EST

Judy,
Wtih all the hoo-ha going on, it's not clear to me that your question about film
washing has really been answered. There are bits and pieces in the various
responses and thought I would add a bit and collect it together.
The time limiting step in film (and paper) washing is the diffusion of the hypo
or whatever from the emulsion into the water. The rate is also determined by
the concentration difference of the hypo in the film emulsion <at the surface>
and the concentration in the water immediately adjacent to the film.
Considering the volume differences between the amount of emulsion and the amount
of water, one could probably do a quick rinse off the surface of the film and
then leave it immersed in one change of water of reasonable volume for a few
minutes <if you agitate the film sufficiently> so that the hypo concentration
next to the film stays low.
Turbulence helps, like using an aerator, or lifting the film out of the water
and putting it back in. In my work (35mm), I fill the tank with water, put on
the lid and shake it for a few seconds, wait a minute, shake, etc. I use three
changes of water in 5 minutes and feel that that is sufficient. It's the
shaking that makes the difference.

If you are using tubes for sheet film, use the tubes for rinsing after hypo,
else if trays, you'll have to slosh around a bit. Come to think of it, those
tubes might be useful if only to rinse out hypo. (I almost wrote hype!)
Paul Simon