Moldmaking

Once your tile is complete, with no undercuts you are ready to make your mold.



Begin by rolling out a slab and cutting it to the size you want your mold to be. The edges of your mold should be 1-1 1/2 inches, so cut your slab 8" by 8".



You want to surround your slab with thick slabs. Cut the sides the length of your slab and 3-3 1/2 inches high. Roll out your slabs 1/2 inch thick and about 8" by 3".



You are making a clay box to contain the plaster.



It is alright if your sides are a little long because you can wrap it around the corner.



Roll out clay coils for any place two slabs meet, and...



...don't forget to smooth the coils into all the corners to keep the box water sealed.



Reinforce the outside edge and corners to prevent blowouts.



Now you are ready to mix your plaster. Make sure to keep your clay wet while you are mixing your plaster.




Always add plaster to water. Sift it gently between your fingers one hand-full at a time. You don't want to agitate the plaster or water yet.



Add plaster until the water can not absorb any more. You will end up with an island like this.


Wait at least 5 minutes before mixing. Plaster will not start to harden until it is agitated, but you want to give the plaster enough time to absorb the water.



Mix gently, keeping your hand under the surface to reduce bubble production. There should not be any lumps. Once you feel the plaster thicken, it is time to pour...



...the plaster in slowly. It is a good idea to mark how high the plaster should reach before you begin pouring. If your plaster starts to leak through the clay (a blowout) try to patch it with a ball of clay.



Bang the board on the table or hit the table with a mallet to force any bubbles to the top.



Once you feel the plaster heating up, it means the plaster is starting to set up. You don't want to try and remove your mold until the plaster starts to cool down. When the plaster is hot it is in its most fragile state.



While waiting for the plaster to set up is a good time to clean up. Including throwing away any chunks of plaster stuck in the clay. We will save the clay to use for future molds, but we don't want it dirty with plaster.



Once the plaster is cooling, you can remove the clay walls...



...and remove the bottom slab and your tile from the plaster mold



You should now have a perfect negative version of your original tile.



All that is left is to clean up your edges and corners...

...and set it out to dry. Set it on two sticks so air can reach underneath the mold for at least a week.