How come some hammers have a peice of glass on top of them

Question

How come some hammers have a peice of glass on top of them

Answer 1

It's not glass, it's resin. It's what they use to glue the fiberglass handle to the steel hammer head.  

Answer 2

If you are referring to the shiny piece that is on top of the head of the hammer directly over where the handle is run through it, it is not glass. It is a melted plastic material that helps to keep the head of the hammer fastened to the handle.