Measuring Small, Distinct Areas of Larger Samples Using the LabScan XE

Lot-to-lot or piece-to-piece color consistency is an important indicator of quality for many colored items. Some items may include multiple small areas of color in one sample, however. Care must then be taken to measure only the area of the sample intended to be measured. A special, small sample port can be used to measure a designated small, colored area on a larger sample using a benchtop 45/0 or 0/45 instrument such as the LabScan XE.

A HunterLab LabScan XE 0/45 spectrophotometer can be used to measure the reflectance of small sample areas carefully positioned over a special, small port plate. This method is recommended by HunterLab for the measurement of small areas on multi-colored samples. The variable sample illumination (VSI) option must be available with the instrument in order to use this measurement method.

The LabScan XE

The Application

Smaller areas on larger samples may have several characteristics that require compensating preparation and presentation techniques in order to ensure a repeatable sample measurement.

• The samples may be translucent and require a constant backing.

• The available measurement area may be very small or not easily differentiated from other colored areas. The proper size port insert must be used to limit the area measured by the instrument.

Recommended Color Scale	CIE L*a*b* as a full color descriptor
Recommended Illuminant/Observer	D65/10°.

Measurement Method

1. Configure your software to read using the desired color scale, illuminant, and observer.
2. Install the 0.20-inch (5-mm) port plate and standardize the instrument for the 0.125-inch (3.175-mm) area of view. If the area of the sample to be measured will not completely cover the hole in this port plate, you may install the CMR 2562 port plate (HunterLab Part Number CMR-2562) with a 3-mm opening instead. First standardize on the black glass, then the white tile.
3. Place the area of the sample to be measured face-down over the sample port and hold it in place, if required, using the sample clamp (HunterLab Part Number D02-1009-200), if available, with the white disk installed. If the sample clamp is not available, use your spare white tile to back the sample. Make sure that the area of the sample to be measured faces the port and completely covers the port opening. Use the retroviewer, if available, to check that the desired sample area is correctly positioned over the port opening.
4. Take a single color reading of the sample. Rotate the sample 90° or move the sample to another area containing the same color and read it at least once more. Average the multiple color readings for a single color measurement. Averaging multiple readings with rotation or movement between readings allows you to better estimate the color of the designated area(s) as a whole.
5. Record the average color values.