How To Measure Translucent Materials

By: Gordon Leggett, HunterLab Senior Application Specialist

Translucent materials offer a significant color measurement challenge since they interact with light in far less controlled manner than most other materials. The color of a material is calculated from measurements of its relative spectral reflectance or transmittance. When light is incident on an opaque non-metal or metal surface, the first surface interaction determines the corresponding perception of gloss and color. Similarly, for transparent materials, light reflected at the first surface is responsible for the perception of gloss, while light transmitted straight through the material gives the color. Translucent materials have both opaque and transparent characteristics. Some incident light reflects off the first surface as gloss, while some enters the material and undergoes multiple scattering and light trapping within the material, resulting in a diffuse pattern of reflectance. In a second interaction, light is scattered and transmitted through the sample, emerging on the other side in a diffuse pattern. As a result, color can be seen in both diffuse reflectance and transmittance, depending on how the sample is viewed.