MOLD: 4a Two or more pieces.
Molds of two pieces or more:
The making of a two-piece mold of a cylinder is described here, and the same procedure can be followed if more sections are needed. They can be used for jars, figures etc. The most difficult part is calculating the measurements, as clay shrinks when it dries and when fired. If the measurements have to be exact, like a tile 15 × 15cm, then one or two should be made, shrinkage can be calculated.
Make a cylinder in clay, mark a line, lengthwise, all the way round the center and then put it on top of the board of wood where the mold is going to be made and leave it to dry. Build up a clay wall right round the cylinder to the height of the line and make a rectangle to the width needed for the mold. The damp clay will not adhere to the dry clay of the cylinder
a) Cylinder of clay
b) Wooden wall round clay wall
c) Clay wall round the cylinder
d) Wooden floor board
Building with wood:
Round the clay build up walls with wood to the height required to cover the cylinder at the top with plaster and to make a thick, strong floor. Clay must be put between the joints of the pieces of wood to hold them together and stop the plaster running. Brush the inside with bleach plus clay.
Prepare the plaster and fill the mold to the top; level it out and leave to dry.
Take off the walls and floor, turn it round and put it back on to the wood so it is standing on the plaster. Take off the clay, which is now at the top, leaving the dry clay of the cylinder uncovered. Indent a small hole in the four corners of the plaster.
a) Wooden board
b) Solid plaster turned round
c) Clay to be taken off
d) Clay cylinder
e) Holes made in the plaster
Now repeat the previous procedure, building up the four walls with wood against the first half that is now solid to the height needed for the floor on top of the cylinder, fill this space with prepared plaster and leave to dry.
Drawing below: mold finished.
Take off the wood and separate the two halves of the cylinder and take out the clay; separate and clean the plaster and you have your mold in two pieces. The holes at the corners have made four small protruding legs on the second part, so when the two halves are put together they will fit correctly and be held in place.