REFERENCE

Plaster of Paris / Moulding Plaster


DEFINITION

This white plaster derived from calcium sulfate, and named after a large deposit found in Paris, France, is ideal for the craft industry. It will harden to a porous, fairly brittle substance when mixed with water, which can be poured into moulds, or manipulated with tools or sandpaper.

It only takes a few minutes to set and will dry to a very smooth finish, and is sensitive to the textures of the mould. Moulds (plastic) can be bought, or manufactured using Dala Modeling Clay or Casting Rubber. It cannot be poured into a mould made from plaster, as it would stick to itself, so a release agent like casting rubber should be used.

MIXING PLASTER

ALWAYS start with the water and then add the plaster. Work in a dust free environment.

TWO RECIPES

SOFT SET

Select any smooth non-porous mixing container and pour enough water in. (estimate quantity from size of object needed) Slowly sprinkle powder into the centre of the container until a peak is formed in the centre of the water. Wait till all the plaster is moist before stirring slowly (no whisking) When all the plaster has dissolved, the creamy mixture is ready to pour slowly. When the mould is full, tap the mould a few times to release air bubbles. Do not be concerned aboute the fact that the drying process liberates heat. Leave to dry till item is not cold or damp.

HARD SET

For a saturated less brittle mixture, sprinkle the powder over the entire water surface till several peaks form. Wait till all plaster is moist and then follow instructions for the first method.

DECORATING

Items can be painted with any Dala Craft Paint or Antique Rub. A quick first layer is necessary to seal the porous surface. It is important to wait until plaster items are completely dry before painting. Seal with any of the Dala Varnishes. It is advisable to leave a small area unpainted (underneath) so as to avoid trapping moisture.



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