1.1 ,This test method describes a steady-state technique for the determination of the resistance to thermal transmission (thermal resistance) of materials having a thickness of less than 25 ,mm. Thermal conductivity may be determined for homogeneous opaque solid specimens (see Note 1). This test method is particularly useful for homogeneous, multilayer, and composite specimens having a thermal resistance in the range from 10 (cm)²·,K·,W^-1 to 400 ,(cm)²·,K·,W^-1, which may be obtained from materials with an approximate thermal conductivity range 0.1 W·,m^-1·,K^-1 to 30 ,W·,m^-1·,K^-1 over the approximate temperature range from 150 K to 600 ,K. It can be used outside these ranges with reduced accuracy for thicker specimens and for thermal conductivity values up to 60 ,W·,m^-1·,K^-1.