Rose didymium is a high luminous transmittance filter specifically designed to absorb bright yellow sodium flare (589 nm) which occurs when heating glass. Didymium lenses protect the eyes from certain visible and UV light produced in the glassblowing process. They enable the glassblower to see the glass while it is being worked in the flame.This is the classic filter that has been used for many years in all types of hot glass applications, as well as kiln working.