Interesting Facts About Plaster of Paris
Plaster of Paris, a quick-setting, bright-white plaster, is an extremely useful and versatile substance. It is featured in our homes as architectural decoration, used for fireproofing buildings or at school and home for arts and crafts, and the medical profession uses it to support fractured bones. Before using plaster of Paris for any purpose, it is important to know the necessary safety precautions and proper preparation methods.
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Chemical Composition
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According to the Encyclopedia Britannica, plaster of Paris is made of calcium sulfate hemihydrate, a fine white powder. It is made by heating calcium sulfate dehydrate with gypsum at a temperature of 248 to 356 degrees Fahrenheit.
History
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Plastering is one of the most ancient handicrafts still practiced. The pyramids in Egypt feature plasterwork that is at least 4,000 years old, some of the finest examples of which are rendered in an identical substance to plaster of Paris. By the early 1700s, Paris was Europe's biggest supplier of gypsum used to make plaster and cement, hence the name.
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Medical Use
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Plaster of Paris is commonly used in the medical industry to make casts. The injured arm or leg is usually wrapped in a layer of cotton padding, then wrapped with plaster-coated bandages. The bandages begin to dry, but are soaked in water when they are used. Plaster of Paris casts must not get wet, or they will soften and become weak.
Safety
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Plaster of Paris is a potentially hazardous substance. Only adults should mix plaster of Paris, and children must always be supervised by an adult when working with it. Wear protective gloves, use a stick to stir it rather than your hands, and avoid inhaling the plaster dust. If you get plaster of Paris on your skin, wash it off immediately; it will burn the skin with prolonged exposure.
Crafts
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Plaster of Paris is commonly used to make castings. You can use candy or jelly molds, or special plaster casting molds. Pour in liquid plaster of Paris, wait for it to dry then remove the shapes. You can trim away rough edges with a craft knife, then paint the plaster shapes. The bright white color of the plaster makes it easy to paint. This technique can be used to make ornaments, refrigerator magnets and pins, among other possibilities.
For Kids
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Plaster of Paris can be used to make your own sidewalk chalk. Mix plaster of Paris according to the directions on the packaging, squeeze in some poster paint and mix it all up with a stick. Use old ice trays or paper tubes with one end taped-over as molds, pour in the colored plaster and allow your chalks to dry for up to 12 hours. For a fun keepsake, pour plaster of Paris into a shallow container, press your child's hand or foot quickly into then right out of the plaster. Immediately wash the skin thoroughly, removing all traces of plaster. When the plaster dries, remove it from the container and mark the date or child's age on the back.
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References
- Photo Credit Plaster head of the ancient Greek philosopher Socrates image by Supertrooper from Fotolia.com
