Removing emulsion from glass plate

[John Jarosz]

Hi all,

I have a couple of old glass plates with an unprocessed emulsion on them. I 'd like to use the plates for another project. What's the best way to rmove the original emulsion? If I simply fix the plate is everything rmoved?

Thanks

john

[Jerevan]

I only have experience with exposed plates, but I think water (or some other liquid) would remove it off from the plate. I'd prefer just to cut a few new glass sheets in the same size (or have someone to do it).

If they have been kept in the dark and are not exposed, they may be of interest to someone here on APUG. There are a few people around who indulge in exposing old glass plates.

EDIT: btw, if you decide to cut plates yourself, be aware that the edges are very sharp. Use something to sand them down a bit so you can handle them safely. Glass cuts can be horrible.

[raucousimages]

Sodium Carbonate in hot water is used to reticulate negs. if you leave it too long the emulsion will just fall off of the film base. Shuld work for plates as well.

[Roger Hicks]

Hi all,

I have a couple of old glass plates with an unprocessed emulsion on them. I 'd like to use the plates for another project. What's the best way to rmove the original emulsion? If I simply fix the plate is everything rmoved?

Thanks

john

Boiling with caustic soda is traditional. DO NOT use light alloy saucepans! For that matter, ask yourself how much you want to use boiling caustic soda solution...

Cheers,

R. (www.rogerandfrances.com)

[Dave Parker]

EDIT: btw, if you decide to cut plates yourself, be aware that the edges are very sharp. Use something to sand them down a bit so you can handle them safely. Glass cuts can be horrible.

I can second, third and fourth this statement!!!! be very careful when handling glass plates that don't have finished edges, I have the scars to prove it!

:o

Dave

[Photo Engineer]

Hot caustic soda will etch glass.

The best is a sulfuric acid / dichromate solution in which you soak the film. Then you wash in hot water and soak in warm detergent solution. Follow this by another wash and then rinse in distilled water and dry.

Use rubber gloves to prevent finger prints.

PE

[Roger Hicks]

Hot caustic soda will etch glass.

That's interesting. I have to admit that this was taken from old books; I had not tried it. I wonder if they just didn't worry about the etching, as they were contact printing anyway.

Perhaps, too, you could throw more light on something else I have read in old books but never verified. It is that you sometimes get a residual ghost image on (or perhaps more accurately in) the glass even when the gelatine is fully removed. Hard to believe, but I have seen it asserted in more than one old source (sorry, can't remember where).

Cheers,

Roger

[John Jarosz]

[QUOTE=Photo Engineer;376962]
The best is a sulfuric acid / dichromate solution in which you soak the film. /QUOTE]

Can you elaborate on the acid strength/dichromat concentration?

Thanks

john

[donbga]

[quote=John Jarosz;376974]

The best is a sulfuric acid / dichromate solution in which you soak the film. /QUOTE]

Can you elaborate on the acid strength/dichromat concentration?

Thanks

john

A concentrated solution of lye or sodium hydroxide (about 10%) will do the trick. No need to mess with sulfuric or dichromate. It may take a bit of soaking. But unless there is something special about the glass I would toss it and start fresh - a more effiient use of your time and money.

[John Jarosz]

It's a long story.

I broke the groundglass element of my Hasselblad "Groundglasss focusing adapter". Don't ask how. The fresnel is fine. I cannot find a source of glass .065" thick. The groundglass is NLA from Hasselblad.

The 2 4x5 glass plates I have are .058 (approx) thick. So the expediant solution seems to be to use the glass to have it ground and sized to fit. I can make some shims to make up the thickness difference.

Thanks for the ideas.

John