I live in an area with what seems like a thrift store on every corner and pewter goods seem plentiful. Not always cheap but plentiful. So I've stocked up. Most of my current supply of "pure" lead is from plumbing pipes my neighbor donated to the cause.
The problem I'm having is an incredibly high cull rate with this alloy in every mold I've tried. Today I was off so spent some time confirming it's the alloy. Well I THINK it is anyway. The alloy btw is very roughly 1 pound pewter to 9 pounds pure lead. The alloy calculator puts this at roughly 90% lead, 9.25% tin, 0.6% antimony, and 0.15% copper. And yes I'm aware that that is based on HUGE assumptions about the actual makeup of the pewter pieces I've used. Measured density of the alloy is around 10.97.
On the UP side, this expands BEAUTIFULLY and holds its weight very well.
BTW I confirmed it's the alloy that is the problem by casting using two other alloys and they worked as expected. Shoot one of them wasn't an alloy at all! I used straight lead and it filled out better than the pewter alloy.
So what's the deal? Did I screw up and mix something else into my pewter? Any other possibilities?