A method of nondestructive testing of thermal conductivity of slab materials using an infrared scanning technique is described. The method uses an AGA Thermovision System 680 to scan the surface of the test specimen. Then by matching the observed temperature with the predicted surface temperature, while treating the thermal conductivity as a matching parameter in the analysis, the conductivity of the material can be determined. The paper spells out details of the design of the apparatus. Calibration of the equipment is also treated in detail. The method is used to test thermal conductivity of glass slabs. The measured data is found in fair agreement with the reported data.