TEACHERS NOTES - The Essential Guide to Successful Plastercasting
What You Will Need:
School’s Pack
Cardboard
Scissors
Pencil
Jars or other Supports
Washing up liquid
Bowl
Access to water
We advise you to demonstrate how to cast a SUPERCAST model before allowing the children to begin. There will be fewer mistakes made this way.
Use a piece of firm cardboard – it must be strong enough to support a heavy model.
Wet the mould and turn its rim inside out, now place it on the cardboard to make a watery print.
Draw round the print and then cut out the shape in the card.
Place the cardboard support on jam jars or other suitable classroom materials. They must be high enough for the mould to be suspended upside down.
Fill the mould up with water to just below the line you will cast to. Empty the water into a mixing bowl and replace your mould in its support.
With a spoon sprinkle the moulding powder GRADUALLY over the water until it starts to settle and show white through the grey mixture. YOU MAY NEED ALL THE POWDER PROVIDED.
Leave the mixture to stand for 30 seconds to 1 minute (enough time to seal any left over powder bags). Then using a spoon stir well to make an even mixture. Do NOT stir too vigorously as this will add air to your mixture and produce air bubbles to your casting.
Pour 1/3 of your mixture into your mould, squeezing it gently to enable the mixture to get into all of the detail.
Top up the mould to the casting line and squeeze gently again to remove any air bubbles. Make sure the plaster base is level, as this will provide an even stand for your finished model.
Leave the mixture to set; this takes about 30 minutes. (The model will heat up as it sets).
REMEMBER: Plaster sets hard and will therefore block drains, sinks, toilets if disposed of incorrectly. ALWAYS wipe bowls with old newspaper to remove most of the mixture and then wash up. DON’T FORGET to wash spoons as well at this stage.
Put some warm water and washing up liquid into a bowl or sink. Remove the mould from its support and half immerse it in the water. Make sure all the outside of the mould is wet, particularly such things as rabbits’ ears or dogs’ tails! This will help the mould to come off without difficulty.
Peel back the rim of the mould, and hold the base of the model. Quickly strip off the mould, pulling quite sharply away from the base.
Wash and dry the mould and store in a dry, dark place.
Leave the model to dry for 24 hours before painting. Acrylics produce the best results but for younger children we recommend poster paints, which are washable and non-toxic.
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The bases of the models may be rough and uneven but they can be rubbed or sanded flat before they have dried out. If available, felt stuck to the base of the model produces quite a professional look and also protects delicate surfaces from scratching.
HOW TO MAKE PLAQUES
Measure the amount of water required by almost filling the plastic mould with water and then pour into a bowl.
Mix powder and water using steps 7 to 11 above, however, instead of squeezing out the air bubbles tap the plastic mould a few times on a table.
Ensure the plaster base is flat and insert at the top of the plaque a piece of string to allow the plaque to be hung on a wall.
After approximately ½ hour the plaque may be tapped out and left to dry for at least 24 hours.
More professional results can be obtained if the plaque is painted first totally in white providing a base coat. After the white paint has dried then the plaque can be painted in acrylics or poster paints, depending on the age group of the modellers.
