Wood's glass was developed by Robert Williams Wood (1868–1955) as a light filter used in communications during World War I. His "invisible radiation" technique worked both in infrared daylight communication and ultraviolet night communications. His glass filter removed the visible components of light beam, leaving only the 'invisible radiation' as a signal beam. Wood's glass is commonly used to form the envelope for ultraviolet fluorescent bulbs (black light).

Wood's glass is special barium-sodium-silicate glass incorporating about 9% nickel oxide. It is a very deep violet-blue glass, opaque to all visible light rays except longest red and shortest violet. It is quite transparent in the violet/ultraviolet in a band between 320 and 400 nanometres with a peak at 365 nanometres, and a fairly broad range of infrared and the longest, least visible red wavelengths.

See also

• Wood's lamp

References

• R.W. Wood. "Secret communications concerning light rays". Journal of Physiology 1919, 5e serie: t IX
• J. Margarot & P. Deveze. "Aspect de quelques dermatoses lumiere ultraparaviolette. Note preliminaire". Bulletin de la Société des sciences médicales et biologiques de Montpellier 1925, 6: 375–378.
• Robin Williams & Gigi Williams. "Pioneers of Invisible Radiation Photography"

Optical filters