Mold Making Instructions: How to Make a Mold for Plaster Casting

Plaster cast textures

How to Make a Clay Mold - Mold Making for Plaster Casting.

You will need 2 lumps of clay (about the size of 1 or 2 fists and some spare). (For a full list of materials needed: see below)

Shape one piece of clay into a ball and roll or flatten it out into a slab (about 2 or 3 cm thick) on a piece of thick card.

Write your name on the edge of the cardboard.

Cut the slab into the desired shape. (A card or paper template can be useful.) If you make any changes, ensure that you seal the base thoroughly - Liquid plaster will be poured into your mold, so if there are any gaps it will leak!

Build up some areas with clay (these will be sunken/concave in the finished cast) + press into (but not right through) the slab other areas, (which will be raised/convex). For instance – if you are making a face, you might want the nose to stick out – so press the nose shape in to the clay.

To add interest, cover any or all of the surface with a variety of pressed in, or built up patterns and textures. Any tool will make all sorts of marks, (depending on which edge you use,) so have a spare piece of clay for experimenting and find out what looks interesting.

The photo above shows some examples of the sort of interesting textures you can get when using a clay mold to cast in plaster - the possibilities are endless!

Shape the other lump of clay into a sausage about 2 or 3 cm thick and long enough to fit around the outside edge of your clay mold. Flatten it and then press the edges together firmly, to build a solid wall (about 4 or 5 cm high) round your clay base. Smooth the join over, making sure it is very well sealed - no gaps!

Your plaster casting mold is now ready for use. Keep it damp if you want to work on your mold making project more later, by wrapping it in a plastic bag with your name and the contents written on it. If the atmosphere is very warm or dry, a few damp paper towels laid over it will help keep it moist.

You will need:

Clay: any type - grey stoneware is ideal - air drying (air hardening) modelling clay and even plasticine or play dough are fine to use, for small casts . Red terracotta or earthen ware will work well, but may stain the plaster. (Note that with care, the clay may be reusable for future mold making - but it will not be suitable for firing as it will have bits of plaster left in it.)

Thick card board to work on - larger than your work. (such as a piece of corrugated card from a cardboard box);

Clay tools (2 or 3 pieces of old or plastic cutlery and a cocktail stick or wooden skewer, will do fine); rolling pin (optional);

Label your work and clean-up:Waterproof marker pen; newspaper; apron, old shirt or old clothes: clay is messy!paper towels or sponges for cleaning upplastic bag (to keep clay work damp).

These Mold Making and Plaster Casting Art Projects will show you how to make plaster casts from clay molds, using masks, faces or skull drawings as your starting point.

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