I make Moais not only by sculpting. Sometimes I'm casting them out of concrete.
I made this form a few years ago. So far, I have managed to cast at least 30 heads.
Before pouring the concrete you need to saturate the molud with something anti-adhesive - in this case - oil
Mixing the concrete: 1 part of cement, 4 parts of sand.
Tie'em up together
Magic spell : "live long and prosper"
Magic spell into the bottle:
Bottle into the mould:
Fill with thin concrete:
After 4 days - half-open mould:
Head removed from mould
Some things to clean up
Some concrete leaks to remove
Time to grind some edges around
Finished. Let him continue to dry
