Pyramids: Cast, Poured, or Both?

Lime is one of the oldest products known to man, and dates back to the stone age. Primitive kilns believed to have been used to produce lime during this era have been excavated and it is believed that lime is the first manufactured chemical to be used by man. In fact lime plaster in reasonably good condition has been found in the pyramids, some 4,500 years old.

Mixed with coal and burned at extremely high temperatures of up to 1,000 degrees centigrade the limestone or calcium carbonate yielded carbon dioxide and calcium oxide also known as quicklime. Although hard work, the method was easy: alternate layers of coal and limestone were tipped in the top of the kiln and the burnt remains removed through the small doors at the base

Draw kilns operate under the principal of gravity. Limestone is fed into the top of the kiln and the cooked stone removed from the bed of the kiln. Fireplaces were located at the sides of the kiln where fuel was burnt to cook limestone. The great advantage of the draw kiln was that it could be operated on a continual basis and was more efficient from the standpoint of fuel economy. Later improvement to the draw kiln, which improved their fuel economy and allowed greater control of the firing temperatures was the introduction of water powered bellows.