Tuesday, 25 September 2007

Patina blues

There's a project by Jane Konkel in the November 2007 issue of Bead Style magazine, which involves adding a blue patina to a copper chain. The photos show a really pretty Winsor Blue result. The instructions were simple, and a web search produced this resource with supporting information, so I decided to have a go. Although the pieces in the article have textured surfaces, I tried the technique out first on a set of smooth wire chain maille earrings I made last year, as they were nice and small.

First step is to soak the copper in salty water, about 2 tablespoons in 150 ml. I left them for 8 hours which is the upper limit of the recommended period given in the magazine.

Next, you need to place the copper in an atmosphere of ammonia fumes. This can be done in a lidded container, with the items suspended above a centimetre or so of ammonia before sealing. Alternatively, sit an open container of ammonia on your worktop, place the copper item beside it and cover both with a lid to hold in the fumes. I made up an arrangement using an upside down glass jar, so that I'd be able to see what was happening without removing the lid. The ammonia to use is household ammonia, which is 9.5% ammonia. I got mine in a local hardware shop. So, I took my salty earrings, suspended them above the ammonia, and retired to bed. The magazine suggests that a period of four to ten hours would be suitable: mine were left overnight for ten hours.

And this is the result, which is rather towards the tarnish end of the patina-tarnish spectrum! The final step would be to spray with a protective acrylic coating, but I haven't done this as the finish isn't really worth protecting, and I may clean it off and try again.

There are clearly lots of variables involved here: cleaning, surface finish, how the salt is applied and how long you expose to the fumes. Worth another go!

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