Measuring Metal Surfaces Using the MiniScan EZ Diffuse
Lot-to-lot or piece-to-piece color consistency is an important indicator of quality for many colored items. Bare, uncoated metal items or those plastic or glass products that simulate a metal surface, can be easily measured at the sample port of a portable diffuse instrument such as the MiniScan EZ.
A HunterLab MiniScan EZ diffuse spectrophotometer can be used to measure the reflectance of metals when the instrument sample port is placed over the sample. This is the method advocated by HunterLab for the measurement of metals that are uncoated if a ColorQuest XE, UltraScan PRO, or UltraScan VIS is not available.
The MiniScan EZ
The Application
Bare metals may have several non-uniform characteristics that require compensating preparation and presentation techniques in order to ensure a repeatable sample measurement.
The samples may be directional, requiring the averaging of several readings with rotation.
The surface of the sample is generally shiny and/or polished, requiring use of the diffuse MiniScan EZ model for viewing the color of the surface, which is seen primarily in the specular reflection.
| Recommended Color Scale | CIE L*a*b* as a full color descriptor |
| Recommended Illuminant/Observer | D65/10°. |
Measurement Method
| 1. Configure your software or the instrument firmware to read using the desired color scale, illuminant, and observer. | |
| 2. Standardize the instrument, first using the light trap to set the bottom of the scale. Make sure the light trap completely covers the port. |  |
| 3. Complete the standardization using the calibrated white standard. |  |
| 4. If the sample is flat, place it, with the side to be measured facing up, on a table top or other flat surface and place the instrument down on the sample. For samples that are not flat, place the nose cone over the sample, making sure that the area of the sample to be measured faces the nose cone and completely covers the hole in the nose cone. |  |
| 5. 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 directionality. | |
| 6. Record the average color values. |