A method for producing optically perceptible laser-induced cracks in brittle material

A method for producing optically perceptible laser-induced cracks in brittle material in which a laser radiation, followed by a jet of coolant to the surface of the brittle material is relatively performed in order to drive from an initial crack starting a crack track into the material and in which the coolant a labeling agent is added, which penetrates to the crack formation in the gap and makes it visible.