I sorted all me weights. I stay by the smelting pot, watching for the occasional one I missed.
Today, 'bout the 4th pot I smelted down, appeared a lone "non-melter" As I scooped it up, one end liquified and left the rest. To my horror, it was a zincer-stinker. It was about a 4 oz weight, and a little less than 1/2 of it melted into the pot. I quarantined the pot full.
So, is 1.5-2 oz in 30-40 lbs enough to be concerned about?
That'd be 3-4% or so, if I did my figgerin' right.