Step 3: Make the mold
Line the box/bowl with plastic wrap as this will make it easier to remove. It will also make a Lego box waterproof and keep it clean. I had a problem getting the wrap into the box and this shows in the mold. It is best if you find a way to hold the wrap down.
To mix the plaster of paris measure how much water it takes to fill the box, that is how much water you should use. Add the plaster to the water a bit at a time and stir until it forms little islands. it should be the consistency of thick paint.
Because I knew i couldn't melt the clay out of the mold I put two tooth picks halfway up the piece so that i could cut the mold in half later. Not pictured I pushed one pick right through and left it there, this caused problems.
Place the piece in the box, as centrally as possibly. Mine was off centre so the mold wall was very thin in some places. Now pour in the plaster. You should do this entire step outside or some where that can get messy, not the kitchen.
Plaster of Paris mixed with water forms a chemical reaction that makes it hard, it doesn't just dry out like clay. This means that if it hardens on you counter or floor you have yo chip it away with a chisel. Think cement. By the same token, don't throw excess plaster down the drain it will harden under water and block you pipes.