Didymium is the classic filter that has been used for many years in all types of hot glass applications. While it was the first material to offer filtering of the sodium flare, it did not offer any infared protection. Newer materials now offer better protection, and as such, we do not carry any glasses with Didymium lenses. However, you may still hear people refering to their glasses as being Didymium's, even if they have newer lens materials.
Schott Glass Technologies developed a contrast enhancement glass for spectacle lenses called ACE (short for Amethyst Contrast Enhancer). This glass utilizes rare earth oxides in the glass composition to achieve the unique color enhancing characteristics. Sold under several brand names (such as AV 2000 and Phillips 202), ACE is the name Schott calls this popular lampworking filter lens material.
ACE is very efficient in filtering ultraviolet (to 390 nm), near infrared, and the sodium flare. The sodium flare is the bright yellow light that hot glass produces while in the flame. ACE also color enhances red, blue and green, making it easier to see a glass' true color and judge its temperature while you work.
The Light Green lenses provide protection in the ultraviolet and infared ranges, and that bit of darkness needed when looking at warm or hot glass. These are good for kiln work (casting, slumping and fusing) and furnace working. These do *not* provide any filtering for the sodium flair.
Phillips Boroscopes, also known as Green ACE, are designed to give the extra protection needed when working with borosilicate glass. Borosilicate is generally worked at hotter temperatures, resulting in more light radiation. Green ACE gives extra protection in the ultraviolet and infared ranges, and the extra darkness protects from the bright glow that this very hot glass gives off, all while eliminating the sodium flare.
Green ACE is available in several 'darknesses'. Green ACE #2 lenses are only a little darker that regular ACE, and therefore are an excellent upgrade in protection when working soft glass, without becoming too dark. Green ACE #3 and #5 are considerably darker than regular ACE. The #3 shade is a good choice for most borosilicate lampworking when working on small to moderate size pieces. The darker #5 shade is suggested for working very large or very hot pieces.
ACE and Green ACE lenses are also available within the same frames.