Measuring Transparent Films and Solids
The instrument illustrated below is an UltraScan VIS. Measurements on an UltraScan PRO or ColorQuest XE would be carried out in a similar fashion.
Lot-to-lot or piece-to-piece color consistency (or colorlessness, for some) is an important indicator of quality for many transparent items. Glass and plastic plaques and films that are transparent should be measured in total transmittance mode on a benchtop sphere instrument in order to assess the color of the item when light shines through it.
A HunterLab UltraScan VIS diffuse/8° spectrophotometer standardized in total transmittance (TTRAN) mode can be used to measure the transmittance of transparent plaques or films that are held in place over the transmission port. This method is recommended by HunterLab for the measurement of flat, transparent solids, including such products as glass panels, transparency sheets, and plastic plaques.
The UltraScan VIS
The Application
Transparent plaques and films have several non-uniform characteristics that require compensating preparation and presentation techniques in order to ensure a repeatable sample measurement.
Plaques or films may contain bubbles or hazy areas that alter the color measurement, requiring the averaging of several readings with rotation.
Films are flexible, and care must be taken that they do not pillow into the transmission port.
| Recommended Color Scale | CIE L*a*b* as a full color descriptor |
| Recommended Single-Number Indices | YI D1925 (2/C), YI E313 when samples are near colorless |
| Recommended Illuminant/Observer | D65/10°. C/2° may also be used. |
Measurement Method
| 1. Configure your software to read using the desired color scale, illuminant, and observer. | |
| 2. Install the transmission clamp accessory (HunterLab Part Number C02-1005-444) at the transmission port (sphere) as described in your User's Manual. |  |
| 3. Standardize the instrument in TTRAN mode, first using the black card at the transmission port. Hold the card in place using the transmission clamp. The large area view (LAV) port plate and lens position should be used for these measurements. |  |
| 4. Complete the standardization by removing the black card from the transmission compartment and placing the white calibrated tile at the reflectance port. (The ColorQuest XT does not require placement of a white tile.) |  |
| 5. Center the sample to be measured over the transmission port and hold it in place and flat using the transmission clamp. Close the transmission compartment door. |  |
| 6. 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. | |
| 7. Record the average color values. |