The kilns are made with either fixed or revolving retorts.
In practice the proximity to chalk pits or lime kilns, the cost of the lime and cartage, will determine which is most economical.
The reliefs upon it are sometimes of considerable beauty, and large quantities of it, and the sites of several of the kilns, have been discovered in and near Arretium.
The drying of the slurry is generally effected by the waste heat of the kilns, so that while one charge is burning another is drying ready for the next loading of the kilns.
The kilns commonly employed are "chamber kilns," circular structures not unlike an ordinary running lime kiln, but having the top closed and connected at the side with a wide flue in which the slurry is exposed to the hot products of combustion from the kiln.
