It is one of the oldest non-destructive examination methods. The possibility to detect the cracks invisible with naked eyes in casts and welding thanks to oiled or watered lime is an examination method known and applied since last century. The method has reached nowadays by passing from several operations. It is an examination method widely used in industry in these days too. If a solid having cracks on his surfaces is submerged in a liquid (penetrant) which is not too viscose, its surface is getting wet and the cracks are filling with this liquid. After the surface drying, the cracks full of liquid appear as wet lines. In radiography, gamma and x-rays which are diffused linearly from gamma and x-ray tube and whose intensity decreases with the square of distance are passed through the materials. These rays attenuate by being absorbed by the material according to the thickness, density and composition of the material. The thick and high density of the piece appear clearly and the thin and low density appear dark on the film. Thanks to this characteristic, it will be possible to determine the discontinuities and errors by appearing darker on the film. The errors can be distinguished from tone contrast with its surrounding. This method can be applied to all kinds of metal as well as non metal materials such as ceramic, plastic.