What is the shell of a welding helmet made from?

Most, entry level, welding helmet shells are made from nylon. Nylon is a good all around material that is lighter than fiberglass and extremely durable. Professional welding helmets are often made with NORYL or AMODEL. NORYL and AMODEL are higher quality materials that will outperform nylon in almost every significant welding-related category. They are a bit more expensive but will last 2-3 times longer than their nylon counterparts.