There are a few causes of the mold not filling out.
- Mold not smoked- see step # 2 in the instructions
- Mold cold- dip the corner of the mold in molten metal
- Oil in the mold cavities- wash blocks with white gas or any other volatile solvent
- Molten metal is not hot enough- increase heat on melter/furnace
- Molten metal is not good- sometimes an alloy just won't work easily.
- Molten metal needs fluxing- see instructions under "Preparing Your Metal"
- Using drop out mold release spray
