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Posted by Sherman in Idaho [72.47.9.37] on Thursday, December 06, 2012 at 17:27:49 :
In Reply to: O/T - restoring copper patina posted by Dave Maher [67.186.188.180] on Thursday, December 06, 2012 at 16:17:47 :
Also called "liver of sulfur". Comes as yellow flakes that stink like sulfur when exposed to moisture. Must be kept in a tight container. It's what jewelers and other craftspeople use to get a tarnished patina on silver and copper. It's apparently also used by photographers for something or other. Depending on how strong you mix it up, it will turn it black in seconds. Then you can polish it to get it back to the antique look. $5 will get you a quarter pound or so from lots of places on-line. If you were nearby, I'd just give you some.
If you just want to take the extreme brightness off, heating it in air for some time, either with a torch or in an oven, will do it. Obviously you don't want to get it so hot that the solder melts, but some heat will encourage it to oxidize faster.