So this thread started out as a response to one of UnOrthodox's threads. I'm beginning to work on one of my projects for this up coming Halloween, and I needed a lot of skulls that look like they're made of stone, so I went looking on casting and forging websites and came across sand casting. What they describe there is making something called green sand. The long and short of home made green sand is go to you local home depot and buy a bag of play sand, sift it through window screen and set aside the fine sifted sand, then buy a bag of self clumping cat litter(this is made of Bentonite), and pulverize it, I used an old blender and ran it till it was a fine powder, combine 30% powdered cat litter and 70% sand. Add water a little at a time and mix thoroughly until the mixture holds together when you squeeze it in your hand. This mix will give you a very smooth clean casting, in other words not what I needed for stone skulls, so I started over, this time omitting the cat litter, and just moistened the sifted sand, this worked great, as you can see below. I use Great Stuff spray foam. This method can be used for casting just about anything you can think of from skulls to small architectural pieces, to really big architectural pieces, to Tombstones. Have fun with it!
I started with a cheap foam skull and cut the face off of it ( I have both with and without the jaw-bone)
I use play sand from Home Depot for the mold:
next I press it firmly into the sand carefully packing the sand all around the foam skull
and remove it from the sand
Add foam and let dry:
It comes out looking like a skull carved in sandstone
That's the long and short of it.