Surface breaking defects are detected using a scanning laser source to deposit heat into a sample surface. Any lateral flow of heat is disturbed by such a defect, with a change in thermal spot shape being detected by an infrared camera. An apparent increase in temperature as the laser passes over a defect is due to a localised change in emissivity, allowing defects to be distinguished from surface markings. Defects have been detected in both stainless steel and aluminium. ► Thermography is used for the detection of surface breaking defects. ► A scanning laser source is used to deposit heat onto a sample surface. ► A change in lateral flow of heat is detected by a thermal imaging camera. ► Apparent rise in temperature as laser passes a defect is due to local change in emissivity.