Removing emulsion

George Collier · Jun 13, 2020

A friend is doing a project which involves coating a varnished surface with Liquid Light, then contact printing (with large negs) an image onto the emulsion. There are times when he would like to remove the finished image and re-coat and re-expose. He is using warm water and not being thorough, although he doesn't see the remaining original emulsion until he has re-coated and is developing the second image. I'm suggesting that he use a strong alkaline solution to remove the first coated image. What would be a good one, in warm water, that would not be toxic to him? Sodium Carbonate?

Nodda Duma · Jun 13, 2020

Add some bleach to a tray of water and let the plate sit in it for a while.

koraks · Jun 13, 2020

Nodda Duma said:
Add some bleach to a tray of water and let the plate sit in it for a while.

You mean bleach as in chlorox, right? That wi indeed effectively strip gelatin emulsions from their substrate. Note that any subbing may also disappear making it difficult to apply a new emulsion afterwards depending on the substrate.

George Collier · Jun 13, 2020

The preference would be something that softens only the gelatin emulsion.

Donald Qualls · Jun 13, 2020

The "subbing" referred to is a coating that helps the emulsion stick -- which, with paint-on emulsion like Liquid Light is whatever the worker applied (on commercial film, it's more gelatin, often a very thin layer and harder than the main coatings).

Bleach might damage the varnish he's working over, however; another option is very hot water. Whatever temperature he uses to spread the liquid emulsion, go at least another 20F hotter. Soak and scrub with a sponge, scrape with a silicone spatula or plastic item, like a credit card, and scrub again.

Nodda Duma · Jun 13, 2020

koraks said:
You mean bleach as in chlorox, right? That wi indeed effectively strip gelatin emulsions from their substrate. Note that any subbing may also disappear making it difficult to apply a new emulsion afterwards depending on the substrate.

True he did say varnish, although that doesn’t fall under the commonly understood meaning of a subbing layer.

The other even easIer way to strip off unwanted emulsion is to run the plates through the dishwasher.

George Collier · Jun 14, 2020

Thanks for the replies so far. No one has responded to the alkaline idea, not a good one?
What I remember is that the alkali component of the developer (called accelerator) is what swells (softens?) the emulsion to encourage saturation of the developing component (called reducing agent).

mshchem · Jun 14, 2020

Really hot water dissolves gelatin, as in Jello. I would get some thick rubber gloves, warm a wet sponge in a microwave and wipe it off. Be careful, a microwave will heat a sponge to where you will burn your skin.

You could try Eazy Off oven cleaner, might dissolve the chair.

Nodda Duma · Jun 14, 2020

George Collier said:
Thanks for the replies so far. No one has responded to the alkaline idea, not a good one?
What I remember is that the alkali component of the developer (called accelerator) is what swells (softens?) the emulsion to encourage saturation of the developing component (called reducing agent).

It's not necessary.

Murray Kelly · Jun 15, 2020

I haven't tried it but Amway Trizyme or NappySan etc would likely strip it off overnight, right down to the base. That may not be what you want exactly but it is an idea.

George Collier · Jun 15, 2020

Thanks for the replies.

Removing emulsion

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