I have about 16-20 lbs. of dental x-ray foil saved by my wife (dental assistant). I have smelted it into ingots. I did not note any problems when smelting.
This stuff is definitely not pure lead. It's a lot harder. I don't have a tester, but I did a quick and dirty test by compressing a nut between the x-ray foil ingot and some known alloy ingots. It appears to be a lot harder than WW and a lot softer than Linotype. I'm guessing it's about BHN 16. Yes, I know it's a guess - but it is definitely hard stuff.
As a new caster, I am a bit concerned that there could be zinc in this stuff. What do you folks think?
Thanks!