I have managed to scrounge a few hundred pounds of floor sweepings out of a rad repair shop and I wonder if antimony can be added to the solder to increase the hardness. the clean ingots are very soft , probably little different from pure lead. due to the fact that each radiator probably had a different solder used during manufacture the lead/tin ratio would be impossible to predict. should I just treat this alloy as pure lead and do a 94 lb solder and add 6 lbs of antimony to get a decent alloy? I'm also assuming the high tin content won't hurt my barrel. if anybody has any advice I'm all ears. thank you in advance.