Steve,
This has been quite the experience in experiments! First off let me say that I am doing this on the cheap. No nice aluminum molds for me. I used silicon caulking for my first pass and did a poor job of it and I was able to make anchors but not to the quality that I wanted. The mold was not very good and it degraded after each pour which is not surprising. Then I made a 2 part Plaster of Paris mold which worked fantastic and I got 1 good anchor out of it but one of the Molds broke when removing the anchor. Still determined I took another approach. I work in the electronics industry and we had some contaminated solder that was going to recycler so I thought I would try the Silicon again with Solder becasue of the lower melting point approx 225deg less than lead. So I made a 2 part mold from silicon and it failed miserably. As I was screwing around with this I made a 1 piece Plaster of Paris mold for pad weights for my decoys since this last batch had no keels which was new for me. The Pad weights turned out great so I made a 1 piece Plaster of Paris mold for my anchors which is baking out in the oven at home right now (As long as my wife did not turn the oven off). I will give a shot tonight and see what happens. I actually remembered to some pictures as I went on the last one to share if they turn out.