Glass Glossary

UV Transmission (UVT)

Last Updated: November 23, 2023

Ultraviolet Transmission (UVT) is a measure of the percentage of ultraviolet (UV) light that passes through a material, such as glass. UV light, which has wavelengths ranging from approximately 100 to 400 nanometers (nm), can have harmful effects on skin, eyes, and interior materials, causing fading, discoloration, and degradation. UVT is an important metric for understanding how well a material filters out UV radiation.

Measurement of Ultraviolet Transmission (UVT)

UVT is typically measured using a spectrophotometer, an instrument that quantifies the intensity of light at different wavelengths. The process involves:

  • Calibration: The spectrophotometer is calibrated using a reference material with a known UVT value.
  • Sample Measurement: The material being tested, such as a glass pane, is placed in the spectrophotometer. The instrument directs a beam of UV light through the sample and measures the intensity of the light that passes through.
  • Calculation: The UVT value is calculated by comparing the intensity of the transmitted light to the intensity of the incident light. It is expressed as a percentage, indicating the proportion of UV light that is transmitted through the material.

Understanding UVT is crucial when selecting materials for windows, doors, and other applications where UV protection is a concern. Lower UVT values indicate better UV filtration and protection against the harmful effects of UV radiation.

UVT vs. ISO-CIE Fade Measurement (Tdw-ISO):

UVT is a more well-known measurement to measure fade potential. But ISO-CIE Fade Measurement, or Tdw-ISO, offers a broader assessment of fading potential, accounting for the whole spectrum of light that contributes to fading, including UV and visible light, in the range of 300 to about 700 nm. The Tdw-ISO value calculates transmitted daylight weighted by the ISO-CIE damage function, which assigns specific damage-weighted transmittance to each wavelength according to its contribution to fading. Lower Tdw-ISO values indicate better overall fade protection. Both metrics, UVT and Tdw-ISO, are important for evaluating materials’ UV and fade protection properties.