Alpha gypsum is a common ingredient for making plaster. Alpha gypsum is made by processing gypsum stone into a fine powder and is well regarded for its strength and low absorptive levels.
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How It's Made
Alpha gypsum is made by calcining gypsum stone under high pressure. Calcination is a process that drives out the moisture in a substance by heating it to a specific temperature.
Alpha gypsum is essentially used whenever more strength is needed, as alpha gypsum will harden to a degree that is much greater than normal plaster.
To make plaster out of alpha gypsum you need to add roughly 22 to 45 pounds of water per every 100 pounds of alpha gypsum and then stir.
One of the negative side effects of working with alpha gypsum is that once it dries, it can usually not be carved or molded as normal plaster can be. This is due to its increased hardness.
Other forms of plaster can be added to alpha gypsum, such as beta gypsum, to increase the strength of the plaster even more.