Gypsum has been used since ancient times to build monuments that last for centuries. The pyramid of Giza in Egypt is the only surviving wonder of the ancient world. This noble material has been a continual presence in construction and renovation through the ages.

Gypsum is a mineral made up of calcium sulphate hydrate and found in sedimentary rock formations in a crystalline form known as calcium sulfate dehydrate and does not support bacterial growth. One hundred pounds of gypsum rock contains about 21 pounds (or 10 quarts) of chemically combined water. Gypsum rock is mined and then crushed. The crushed rock is ground into a fine powder and heated to about 350 degreesF, which removes three fourths of the chemically combined water in a process called calcining. The calcined gypsum (or hemihydrate) is then used as the base for gypsum plaster, gypsum board and other gypsum products.

In order to produce gypsum board, water and additives are mixed with the calcined gypsum to form a slurry which is fed between continuous layers of paper on a board machine. While the board moves down a conveyer line, the calcium sulfate recrystallizes or rehydrates, reverting to its original rock state. The paper becomes chemically and mechanically bonded to the core. The board is cut to length at this point and conveyed through dryers to remove any free moisture.

Gypsum manufacturers also rely more and more on synthetic gypsum as an effective alternative to natural gypsum ore. The former is a by-product, or waste material, from other manufacturing processes, mostly the manufacture of titanium dioxide used in paint and the desulphurization of flue gases in fossil-fueled power plants. Located primarily in the eastern United States, these manufacturing or power-generating facilities are more than happy to ship a steady supply of production waste to nearby gypsum board manufacturing plants.

As odd as it may sound, the Chinese eat Gypsum. It's known that there is a certain amount of gypsum in some of the foods we eat. They don't eat it by itself but in a finely powdered state that is mixed with a sort of bean jelly. The bean flower is boiled first and then strained then allowed to settle into a curd or jelly. Once the gypsum is added it acquires greater solidity. It's then cut into small squares.

It's also known that large quantities of gypsum dug out of quarries in northern England are sent to the manufacturers of mustard in Durham as well as to pastry cooks and confectioners in London.