Low Poly Skull Coffee Tamper for casting

I needed a coffee tamper so here we are. If you hack off the the sprue, you can use this 3d print as is, however I wanted a solid pewter coffee tamper so that's what this is for. Obviously you can use this to cast bronze, brass, or aluminum too.

I printed with PLA, 10% infill, 0.7mm walls.

I glued the sprue to the bottom of a container and filled it with a mix of very fine sand and plaster of Paris (2:2:1, sand, plaster, water; save yourself some trouble and pre-mix the sand and plaster be