by Dr. Cadmium » Mon Dec 24, 2012 9:27 am
You need to separate the silver contacts from the bus bars, which are usually copper but can also be made of brass or steel.
To do this, you'll want a mapp gas or oxygen-acetylene torch, definitely the later if you have a lot of material to go through. You'll also want a full-face respirator because of the dangerous fumes. I have read that many, if not most of these contain cadmium in the solder but I do not know for certain.
Apply heat to the back of the bus bar where the silver button is and heat until the section is red-hot. Then use a thin-edged tool like an old kitchen knife to slide the button off. With a little practice, this takes minimal force. You shouldn't have to tap or bang the piece to free the slug; if you have to do this you need to heat the piece hotter before trying to separate it.
These buttons are usually 90% silver or better. Not all refineries will take them, and those that do seem to either charge a higher processing fee or return lower results (I assume because of the cadmium and other contamination).
The ones with patterns on them that look like waffle irons are usually only 40% silver and the rest is partly or mostly tungsten. These are obviously more difficult to process.