1. A method of analysis of schlieren, said method comprising the steps of: a) irradiating a test sample with light from a light source; b) producing a shadow image of the test sample on a projection screen; c) receiving the shadow image of the test sample projected on the projection screen in an electronic image receiving device; d) processing the shadow image received in the electronic image receiving device to measure schlieren image contrast; and e) comparing said schlieren image contrast measured in the shadow image of the test sample with schlieren image contrast of a shadow image of a schlieren pattern of a comparison sample and evaluating the schlieren of the test sample by means of the comparing.