Schluffner graining is a special effect that can be observed in glass and other transparent materials where small grainy particles are visible on its surface. This effect occurs due to the structure of the material, which creates optical changes on the surface of the glass.
Schluffner grain can be visible on a smooth plane or on curved surfaces such as lenses. It looks like a not entirely smooth surface on which small particles are visible. This happens due to the optical properties of glass, or more precisely, the quartz from which it consists.
Transparent materials such as glass or crystal are good conductors for light to enter our eye. Quartz and other materials in glass or crystal create different edges and irregularities on the surface that can prevent light from spreading across the entire surface. This is where the shadow appears and the result is the appearance of small grains on the surface.
The grains visible on the surface are shallow and