Black and white photo paper remover silver gelatine

[clicktheshutter]

Hi

I’ve been looking at chemagraphs lately and I wanted to know if there was a way to partly remove the silver gelatine layer before you develop and fix the image. You get odd tones like yellow and browns, I have seen this on a site that refers putting the exposed paper into a chemical bath before developing but no indication as to what is in the chemical bath

Any help would be appreciated

Chris

 

[StephenM]

You could try sodium hydoxide (extremely caustic!) assuming you can get any; given that gelatine dissolves in warm water, boiling water over the surface should have some effect; I've heard that ascorbic acid (if used in a suffieciently high concentration) will have rather more effect than just as a developer.

You should be able to experiment in the light since all you want to verify is a surface effect.

 

[dmb]

Think this is what you are after. https://en.m.wikipedia.org/wiki/Mordançage


WARNING The way the formula is written is not the way to make this safely. You start off with 700 ml of water. Add other chemicals to the water and then top up to 1000ml. Even better would be to make up with more dilute solutions of acetic acid, hydrogen peroxide and copper chloride, but that requires more mathematics.

 

[StephenM]

What's the problem with making up the formula in the sequence given? Just curious.

 

[dmb]

Adding water to concentrated acid is a very bad idea. It generates a lot of heat. Adding other chemicals to high concentration hydrogen peroxide can produce a lot of heat and release oxygen.

 

[StephenM]

Adding water to concentrated acid is a very bad idea. It generates a lot of heat. .

Not every acid. The only common one I know is sulphuric. Certainly there's no problem with nitric and hydrochloric. Actually, sulphuric is the ONLY one I know.

 

[john.margetts]

What's the problem with making up the formula in the sequence given? Just curious.

When diluting anything at all, you should always add the concentrate to the solvent. The reason for this is splashing. When adding one liquid to another, any splashes will come from the liquid being added to, not from the liquid being added. If you add water to an acid, splashes will be the acid. If you add acid to water, splashes will be water.

 

[clicktheshutter]

Thanks for the replies Mordançage looks interesting, but can you use it on the paper before you develop. I don’t want all of the emulsion lifting just in small areas

 

[dmb]

Hydrogen peroxide on its own will soften gelatine. The 9% solution you can get from any pharmacy should do. The concentrated solution mentioned on the Wikipedia article is not generally available to the public due to it being an ingredient in improvised explosive devices.