Hellma BestCeller are manufactured from various types of glass. The most important criterion for the choice of a particular type of glass is the spectral range for which the cell is intended. Coloured logos are fused onto each Hellma cell, thus indicating the spectral range over which the cell can be used.

In general we divide the glass materials that we use into two groups: quartz and optical glass. Quartz consists exclusively of silicon dioxide (SiO 2 ) and shows some remarkable properties:

  • Quartz displays a high UV transmission, in highly purified synthetic quartz down to well below 200 nm.
  • The thermal expansion of quartz is extremely low, its coefficient of thermal expansion being 6 x 10 -7 K -1 between 20 C and 300 C.
  • Quartz is chemically very resistant and maintains its shape, even at high temperatures up to approximately 1000 C.

Common criteria for all types of optical glass are:

  • that the cells made from it are used in the visible range of the spectrum
  • that the glasses we use are characterised by relatively low values of refractive indexand dispersion
  • that they display good resistance to chemicals.