How to Cast Cement & Perlite
A mixture of powdered clay and limestone, cement must be mixed with some sort of aggregate and water to become concrete: a durable, weather-resistant, workable material suitable for paving, forming or casting into a rubber mold to create sculpture and ornaments. Common aggregates include sand, rock and perlite; perlite, a volcanic glass with a high water content, is a popular choice for artists looking to create lightweight decorative pieces. It is essential to wear adequate protective equipment, including a respirator, when casting perlite concrete -- concrete is highly alkali and can cause external and internal burns.
Things You'll Need
- Protective gloves
- Respirator mask
- Portland cement
- Dry pigments (optional)
- Large basin or wheelbarrow
- Wooden dowel
- Water
- Perlite mix
- Trowel
- Rubber mold in desired shape
- Vegetable oil in spray bottle
Instructions
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1
Put on protective equipment and respirator mask before beginning.
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2
Pour portland cement into the basin or wheelbarrow, and then add any dry pigments you may be using to color your concrete.
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3
Mix the dry ingredients well using a wooden dowel.
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4
Add water slowly, mixing as you add. Continue to add water until the cement is the texture of a milkshake.
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5
Add perlite to the mixture. Usually you will add an amount of perlite equal to the amount of Portland cement. Always defer to the manufacturer's instructions.
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Mix the perlite into the cement to form concrete.
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7
Spray the inside of your rubber mold with a generous amount of vegetable oil.
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8
Pack your mold with the perlite concrete, spooned up using the trowel.
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9
Tap and shake the mold as you pack. This process ensures the concrete fills all areas of the mold and dislodges air bubbles.
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10
Allow the concrete to dry inside the mold. Depending on the thickness, size of the mold and the humidity in your area, drying can take between 2 and 24 hours.
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11
Peel the rubber mold from the dried perlite concrete casting. Repair any cracks of chips with fresh concrete and allow to dry.
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