Removing Silver

[holmburgers]

Care to share exactly what it is you're doing? Inquiring minds want to know!

[peeniwali]

Yeah i knew this was coming. Still have no snappy response so I might as well just come out with it. I am removing silver from a coated fabric while masking off the parts I want to keep. I wanted to do it in my darkroom so the extra chemicals could find a useful afterlife in my darkroom.

[dehk]

Simple household bleach will do it. It'll take the emulsion off.

[Murray Kelly]

50g of copper sulfate and 50g of common salt per litre will strip it off and not ruin the nylon. If there is a lot to do it's easy to make stronger, for convenience.
It rehalogenates in 5 mins or so but I forgot a strip recently for an hour and it was down to clear base.
Otherwise rehalogenate and dissolve the silver salts off with hypo. Still pretty easy on the nylon.
Murray

[peeniwali]

copper sulfate and table salt strips metallic silver? Really? If so, thats pretty nice.

[Murray Kelly]

The black on B&W negatives is metallic silver. Very fine filaments, but metallic silver none the less.

[peeniwali]

i will see if I can order up some copper sulfate and give it a whirl, thanks Murray.

-Peeniwali

[Murray Kelly]

Go to the garden section of the local hardware store. Comes in half kilo or 1 pound packs and may be labeled 'bluestone'.

[mattmoy_2000]

I've seen prints partially destroyed (for artistic effect) using copper sulphate bleaching.
If you're interested in the opposite of how this works, you can take tarnished silver, and put it in a bowl of table-salty water, touching a (large) piece of aluminium foil. The silver goes shiny again, because the oxide transfers to the more reactive aluminium.
I suspect that the CuSO4 bleach works by a similar mechanism, whereby the Cu2+ is reduced to Cu or Cu+, and the Ag is oxidised to a Ag+ ion, forming AgCl (or Ag2SO4?) which presumably can then be dissolved in fixer.