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Emulsion
05-28-2007, 06:32 AM
Hi,

I have access to lots of light/age damaged black and white 35mm film.

I was thinking of experimentally re-coating this film with emulsion.

What is the most cost efficient way of removing the emulsion? Household bleach?

PhotoJim
05-29-2007, 03:35 PM
Fixing it is probably the easiest way. Sodium thiosulfate isn't very expensive.

ben-s
05-30-2007, 03:19 AM
As Jim said above, you could fix it out, but this wouldn't actually remove the emulsion, and the old emulsion might interfere with a new coating.

A sodium hydroxide solution works well, and (apparently) helps prepare the base to receive a new coating.
I have used it to strip 35mm and 120 films, both b&w and colour.

Sodium hydroxide is nasty stuff, especially in the strong solution needed to destroy the coating, so you need to handle it properly.
In this application, it works by dissolving the gelatin. However, if you get it on you, it will dissolve you as well, so wear appropriate PPE.

If you want to recover the silver from the film, fix it first and silver recover the fix, then dump the film in NaOH.


A safer way to remove the emulsion might be to immerse the film in hot or boiling water, and thus melt the emulsion off. I haven't tried this, but I can see it finishing up as a gooey mess.

Emulsion
05-30-2007, 04:51 AM
Thanks for the interesting replies.

I successfully used hot water on some 35mm B&W film and the emulsion was easily removed. The hot water was roughly 90 celcius and the emulsion rolled off the base. The film base is clear and has no signs of emulsion. Both sides of the polyester (not acetate) base appear equally smooth.

Is it possible to re-use the emulsion by somehow removing the silver (fixer?) and mixing with fresh silver nitrate solution? The advantage of recycling the emulsion would be that it already has sensitising dyes, anti fungal chemicals etc.

ben-s
05-30-2007, 07:34 AM
Is it possible to re-use the emulsion by somehow removing the silver (fixer?) and mixing with fresh silver nitrate solution? The advantage of recycling the emulsion would be that it already has sensitising dyes, anti fungal chemicals etc.

I'm glad to hear you've had success with hot water. I'll have to try it myself.

You can't recycle the emulsion.
You will almost certainly have washed the dyes out of the emulsion, and AFAIK they react with the grains anyway.
The only directly recycleable bit is the base, if you can find a satisfactory way to coat it.

If you want to get as much as possible from the old film, recover the silver.
One of my colleagues used to work in a school science lab, and he managed to recover the silver from used fix.
I can't exactly remember how he did it, but I seem to recall he evaporated it and heated the resulting solid in a crucible.
I'll ask him what he did when he gets in.