Apparatus for detecting cracks in optically transparent articles e.g vials, comprising a mount for the article, a light source to direct light at a mounted article, an optical detector positioned to receive light from the light source passed through the article and to generate an electronic signal responsive to received light, first and second (analyzer) polarizers such that light from the light source passes through the first polarizer then through the article, then through the second polarizer on its path to the optical detector, with an optical wave plate positioned between the mount and the second polarizer, and an image processing system to process the electronic signal generated by the optical detector and to indicate the presence or absence of a crack in the article supported on the mount. A method of crack detection using the apparatus is also provided.