Manufacturers of optical coatings and components

Schott UG series filter glass appears black or dark blue, and transmits ultraviolet energy in the 200 - 380 nm range.

All of the UG series glasses are resistant to staining.  UG11 is more susceptible to acid etching than either UG5 or UG1.  UG5 is more susceptible to alkali attack than either UG5 or UG1.  Both UG5 and UG11 exhibit clouding of the polished surfaces after a few months, even during normal storage.

Prolonged exposure of UG series glass filters to UV radiation, particularly l < 320 nm, causes an irreversible reduction in transmittance and a shift of the short wave cut on wavelength to shorter wavelengths.  This solarization effect is UV intensity dependent, and eventually saturates.