Measuring Coated Glass

Note: The instrument illustrated below is an UltraScan PRO. Measurements on a ColorQuest XE, UltraScan XE (no longer sold), or UltraScan VIS would be carried out in a very similar fashion.

Lot-to-lot or piece-to-piece color consistency is an important indicator of quality for many items, including coated glass or plastic that is used in architectural applications. Pieces of coated glass can be easily measured at the reflectance port of of a benchtop sphere instrument such as the UltraScan PRO.

A HunterLab UltraScan PRO Diffuse/8° spectrophotometer can be used to measure the coated surface of glass or plastic pieces that are placed over the reflectance port, while negating any transmitted signal from the measurement by backing the sample with the light trap. This method is recommended by HunterLab for the measurement of coated glass and plastic.

The Application

Coated glass and plastic pieces may have several non-uniform characteristics that require compensating preparation and presentation techniques in order to ensure a repeatable sample measurement.

• As they are not opaque, these transparent samples exhibit light trapping and will be sensitive to ambient light and to small differences in the optical path of the instrument. Backing the sample will make the sample effectively opaque and provide a constant background for the measurement.
• The samples may be directional, requiring the averaging of several readings with rotation.

• Recommended Color Scale: CIE L*a*b* as a full color descriptor
• Recommended Illuminant/Observer: D6510°.

Measurement Method

Configure your software to read using the desired color scale, illuminant, and observer. Standardize the instrument in Reflectance - Specular Included Included mode for the largest port size possible for which the sample can completely cover the hole in the port plate. First standardize on the light trap, then the white tile. Center the sample to be measured over the reflectance port and back it using the light trap. You may want to use the custom light trap shown here for ease of use. (HunterLab Part Number CMR-2870) Make sure that the area of the sample to be measured faces the port and completely covers the port. Take a single color reading of the sample. Rotate the sample 90° and read it at least once more. Average the multiple color readings for a single color measurement representing its color. Averaging multiple readings with rotation between readings minimizes measurement variation associated with non-uniformity or texture. Record the average color values.