In the spectral range from about 310 to 2200 nm the absorption of DURAN® is negligibly low. It is clear and colourless. Fairly large layer thicknesses (axial view through pipes) appear slightly yellow/greenish.
Amber-coloured DURAN® products are suited to use with light-sensitive substances. This results in strong absorption in the short-wave region up to approx. 500 nm. In photochemical processes the light transmission of DURAN® in the ultraviolet range is of particular importance. The degree of light transmission in the UV range indicates the ease with which photochemical reactions can be carried out, for example chlorinations and sulfochlorination. The chlorine molecule absorbs light in the range from 280 to 400 nm and thus serves as a transmitter of the radiation energy..
Amber colouring enables storage of light sensitive substances in DURAN® products. Light transmission in the wavelength range between 300 and 500 nm is, in comparison with DURAN® clear glass, < 10%. Accordingly amber DURAN® glass corresponds to USP/EP regulations.
To colour an existing piece of DURAN® glassware is sprayed using an innovative process with a special medium-diffusion ink solely on the outside of the clear glass. The piece is heated to a high temperature which mobilises the diffusing ions into the out layer of glass. On cooling, the ambering is very uniform, resistant to chemicals and cleaning in a dishwasher. The proven DURAN® properties within the bottle remain unaffected; there is no contact or interaction between contents and amber coating. The uniformity of the amber colouring process and the resultant quality of the amber colour is ensured by continuous monitoring.
- Transmission curves for DURAN®