A cylindrical vessel in which a mud sample can be heated under pressure. Cells, often called bombs, are routinely used for static-aging and hot-roll aging of mud samples. Cells are usually made of metal or metal alloy, such as stainless steel or aluminum bronze, and have open tops. Caps should be fitted with a valve so that gas pressure can be applied and then released before opening the cell. Common sizes are 260 and 500 cm³, to accommodate half- and one-barrel equivalent volumes, plus space for thermal expansion. Glass or plastic jars can be used judiciously when pressure is nil and temperature is limited to below about 150掳F (66掳C).