The specified method is used for determining the pyrometric cone equivalent (refractoriness) of siliceous, low alumina fireclay and fireclay refractory materials and products. Its usefull range of application depends on the availability of suitable pyromeric reference cones. It may also be used for roughly determining the refractoriness of other refractory materials. The pyrometric cone equivalent of the test material is expressed by the number or numbers of the pyrometric reference cone or cones.