A method of inspecting a heatable glazing is disclosed. A heatable glazing comprises a heater array having at least one heater wire. The method comprises the steps of (i) illuminating the heatable glazing with a light source to produce a shadowgraph image of the heatable glazing; (ii) passing a sufficiently high electrical current through the heater array such that the heater wire is observable in the shadowgraph image of the heatable glazing, such a shadowgraph image of the heatable glazing being referred to as an active shadowgraph image of the heatable glazing; and (iii) capturing the active shadowgraph image of the heatable glazing with an imaging sensor. Apparatus for carrying out the method is also disclosed.