Art Lessons: How to make Plaster Casts

These art lessons will show you how to make plaster casts from clay molds, using masks, faces or skull drawings as your starting point.

Before you begin your art lesson, collect together some design ideas, such as African Masks, Aztec or Mexican Day of the Dead Skulls, Cyborg, Alien, or Robot faces or heads. Check out Surrealism and Science Fiction or Fantasy Art for some weird and wonderful art resources. Famous artists, such as H.R. Giger and Eduardo Paolozzi are amazing sources of inspiration.

These ArtyNess images would be great starting places for students' designs. These are all free printables, large enough to use in the classroom as visual resources for Art Lessons.

Cyborg Design Devil Design Demon Design Skull Stencil Day of the Dead Design Profile Skull  Design How to Draw Faces Fantasy Art Ideas

When you have some images, display them where they can be easily seen during your art lessons, so that you can refer to them as you work – they will enhance your imagination and creativity.

It is fine to start by working with clay, or you may want to spend an art lesson drawing your design out first with pencil and paper. Think about different head shapes/ features/ patterns/ textures.

Art Lessons: How to Draw your own Fantasy Art Design

African Mask Plaster Cast

ART LESSON: How To Make a Plaster Cast from a Clay Mold:

*IMPORTANT: Read the Health and Safety Notes below and create a risk assessment. Using Plaster of Paris can be great fun and safe - but ONLY if the instructions are followed and the process understood. Further advice from NSEAD

Clay and plaster are always very messy! Work where the floor and surfaces can be easily cleaned. Cover everything with newspaper and/or plastic sheeting and wear old clothes and an apron or old shirt. Tie long hair back. Remove rings and bracelets. Have a bucket of soapy water, sponges and a floor mop handy for clearing up any spills. Leave plenty of time for clearing up.

You will need:

Clay - any kind; a piece of thick card to work on (such as corrugated card from a cardboard box); rolling pin (optional); clay tools (2 or 3 pieces of old or plastic cutlery and a cocktail stick will do fine); water; pen; newspaper; apron; paper towels; plastic bag (to keep clay work damp) Large flexible plastic tub (a 1 or 2 litre ice cream tub is ideal); plaster casting powder (Plaster of Paris)*; water.

For safety have available: Goggles; Dust masks; rubber or disposable gloves; a water spray for keeping the dust down when clearing up.

How to Make a Clay Mold

Take 2 lumps of clay (about the size of 1 or 2 fists and some spare), shape one lump into a ball and roll or flatten it out into a slab (about 2 or 3 cm thick) on the thick card. Write your name on the edge of the cardboard.

Cut the slab into a mask or face shape.

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 – you might want the nose to stick out – so press the nose shape in to the clay.

Then cover the whole face or mask with a variety of pressed in 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.

This photo shows some examples of textures.

Patterns and Textures in a Plaster Cast Shape the other lump of clay into a sausage long enough to fit round the outside edge of your clay face or mask. Flatten it and then press the edges together firmly, to build a solid wall (about 4 or 5 cm high) round your clay face. Smooth the join over, making sure it is very well sealed. Liquid plaster will be poured into your mold, so if there are any gaps it will leak!

Mold Making Instructions: Printable Worksheet

Making a Plaster Cast:

Stand the clay mold, still on the card, in a plastic bag (to catch any leaks or spills)

Estimate the volume of your mold and use about ½ - 1/3 that volume of water – and put into a plastic tub.

Now the fun part…

Slowly add the plaster powder by sprinkling a handful at a time, all over the surface of the water, until small islands of plaster appear. Try not to drop large lumps of powder in. DO NOT GET WATER INTO THE PLASTER POWDER!

Mixing Plaster

When the water is almost saturated with casting powder, mix the plaster, checking for lumps (squash them – and mix them in). You need a smooth consistency like thick pouring cream. Pour the liquid plaster slowly into your mold.

Remember that once the plaster is mixed it will begin to get hot (UP TO 60C) and set hard within a few minutes - Clean your hands and skin immediately.

plaster cast setting Plaster setting

Shake the mold gently to remove air bubbles. (Hold the card to do this.)

Leave the plaster to set – at least overnight, but a week is better. Notice how the plaster heats up as it sets – this is due to a chemical reaction.

Large quantities of plaster can get very hot as it sets - UP TO 60C (Hot enough to cause severe burns)- DO NOT KEEP YOUR HANDS OR SKIN IN SETTING PLASTER

After it has cooled, keep the clay slightly damp by wrapping it with a plastic bag.

Look Here for Art Ideas to try while you are waiting for the plaster to set… Carefully remove the clay – pick out any bits with a cocktail stick or similar (or your finger nail). (The clay is easier to remove from the plaster if it’s still a bit damp.) Keep the used clay damp in a clay bag (strong plastic), to be recycled. (Remember it will probably have bits of plaster in it – so it’s best used for similar projects. DO NOT REUSE THIS CLAY IN A KILN - it may explode.)

Your plaster cast is now ready to paint. Use any water-based paint, and finish off with a coat of varnish. (Watered down P.V.A. glue works very well)

Look here for ideas for Art Lessons about Color

Cyborg Plaster Cast

*Health & Safety - A risk assessment should be carried out before using plaster.

Do not inhale or ingest plaster powder. Use a light spray of water to minimise dust when clearing up.

Large quantities of plaster can get extremely hot as it sets - UP TO 60C - DO NOT KEEP YOUR HANDS OR SKIN IN THE PLASTER AS IT SETS - clean your hands immediately after mixing.

To clean your hands – wipe as much wet plaster off as you can, using disposable paper towels or even newspaper. Wash with lots of soap and lots and lots of water.

If plaster gets splashed into eyes or hair, rinse immediately with plenty of cold water.

If you have sensitive skin, use plastic gloves. A light coating of petroleum jelly or barrier cream will give a little bit of protection.

Do not pour wet plaster down the sinks.

If using plastic sheeting – put newspaper on top to soak up any spills. Mop up any spills on the floor immediately and remember that wet floors (and wet plastic sheeting) are slippery.

A Guide to Safe Practice and Emergency Procedure

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