The only useful bits I have for you are to use natural PLA rather than coloured, as the coloured leaves behind a dust residue from the pigment (we were burning off the PLA and pouring molten glass in the one kiln process). I usually dry plaster parts in the sun for a few days (obviously depends on the size), and when you are ready to use, warm/heat them in the kitchen oven – as much as you are game – prior to pouring in the molten material. If you do not heat the plaster first, you get too much gas coming out of the plaster – expansion – that it can mar the surface.

One of my "to do" projects is to make some valve castings out of bronze usiing a similar method using wax filament for printing. Wax filament melts at 140-150 Deg C.

After baking the plaster mould to remove the wax it is placed in a box and surounded by compacted sand for extra support while casting.

Paul.