I made a trip to my local scrapyard yesterday. I intended to look for some pure lead for slug casting. They usually have some lying around. I couldn't fill my bucket fast enough when I opened the lid of the dump container. A large spool of solder, probably 2-3 lbs and a folded up ball of solder, at least 4 lb. After I pulled those, I then noticed a couple unmarked solder bars, and full bar of pure tin! What a score! All for $.40 a lb. And I picked up 30 lb of nice roof flashing that's as pure as snow. I can almost tear it with my hands. This is the 3rd time I've scored tin solder at this yard. If you have one in your area, it might pay to drop by from time to time.
One bar (two small pieces) is stamped "cast iron solder". It is very hard, but clearly a lead alloy. Any idea what it might be? Also, the birds nest of solder has a darker hue to it than the spool. I'm not a solder expert, so I'm unsure of what that implies. Any input appreciated.
I seem to remember a topic being discussed previously regarding a member here who offers metallurgy testing. Is there a member or place that will do this for a reasonable price?