I've a number of questions that center around the lead, the heavy, thick 'dross' (slag), the differences of how the alloy casts in separate molds. If you will allow, I'll post pictures to help tell the story.
Saturday afternoon I reluctantly began a casting session. I put it off because the 36 caliber boolts can cast fantastic, or terribly peaky. This is a newer aluminum 2 cavity PB/GC mold. The PB cavity will tend to not fill all so well compared to the GC side, but the GC cavity holds them hostage frustratingly tight. I hoped to cast at least 100 of each, but that meant there would be almost twice that many pours to accomplish if this was to be what I've come to expect. (yes, I did everything the mold maker instructs to do. Not knocking the work, it looks wonderful, but the casting sessions aren't enticing) I ended up with 95 of the GC's and 80 of the PB. If I were to be even more picky the numbers would drop even more.
As for the lead, it is Range Scrap I melted into pucks 3 years ago. It isn't necessarily hard, but stiffer than plumber's lead by quite a bit. I've added a handful of monotype into the pot to harden it up a bit, but as the picture shows that all becomes a thick oatmeal mix on the top that has to be skimmed off:
Attachment 296252
A goodly pile of waste is then spooned out to harden:
Attachment 296253
When that is accomplished the mix is a good melt of alloy that casts well, when all things are as they should be, shoot very satisfactorily and expands in water jugs without coming apart into little shards. Just what I am looking for.
Attachment 296254
As an aside: when I reached the point of putting the mold down a new to me / older steel 4 cavity Lyman 357156 mold caught my eye in the bucket. I had purchased it last fall at a show and had not used it but only tested it months ago. I didn't have a mallet big enough on hand to cut the sprue and abruptly stopped then. This time, though, I laid down a plank of Hickory to hit the sprue plate wing against and for interest sake I poured the lead into all four holes. They weren't good, as the mold was cold, but they had promise, so I kept it up until all 4 cavities dropped really nice SWC Boolits. It didn't take long, either. This was reminiscent of casting thousands of pure lead muzzleloader slugs with steel molds 30 years ago, which were pure joy compared to my work with the aluminum molds These 357156's were so gratifying that I cast 200 of them, enjoying the session more than I could have imagined.
Once this time of casting ended I added more range scrap to the pot Without any monotype. I am wondering if the oatmeal is coming from the hard alloy or ? I suppose when I heat it up again it will tell the tale. When melting the range scrap into pucks originally there wasn't much dross to deal with, and none that I recall that looked like this mush that comes to the surface.
I keep the Lee 20 lb pot on high in the cold garage (30+F)
I don't think it is zink or the alloy under the slag would be contaminated from everything I've read
If you have any thoughts on this that would be helpful.