Question

why does a welder use a special glass while welding?

Answer 1

Welding involves high temperatures, in a typical flux coated arc welding temperatures may be as high as 8000K. In this high temperature light comming out of the welding zone mostly contain the invisible ultraviolet radiation that are vry damaging to the eyes. Thus, helmets with special optical filters are used. Apart from this, helmet provides an additional protection against sparks, fume and splinters.