Measuring Powder Using the ColorTrend HT
The color of powders that are used in manufacturing, such as limestone or raw pigment powders, is often measured to evaluate how the manufacturing process is proceeding or to estimate the color of the final product. In other cases, the powder may be the final product itself, such as cosmetic facial powder or baking powder. Color measurement of these types of products is often necessary to ensure lot-to-lot color consistency before they are shipped to the end user.
The HunterLab ColorTrend HT can accurately assess the color of powders and can detect changes in powder color.
The ColorTrend HT
The Application
Powders have several non-uniform characteristics that require compensating preparation and presentation techniques in order to ensure a repeatable sample measurement.
Powders come in the form of fine particulates—not a solid sample—and must be measured in a batch held on a flat surface in order to be effectively made into a solid.
Powders are transparent--not opaque. Using a sufficient sample thickness and reading the powder on a constant, opaque background will render the sample effectively opaque.
| Recommended Color Scale | CIE L*a*b* as a full color descriptor |
| Recommended Single-Number Index | Yellowness Index, Whiteness Index. |
| Recommended Illuminant/Observer | C/2°. |
Measurement Method
1. Position the ColorTrend HT over the product. A bed depth of 0.5-inch of powder is required for the powder to appear opaque to the instrument. The ColorTrend HT viewing window shoud be 3-4 inches from the product surface. The instrument can compensate for height, so small differences in the presentation of the powder to the sensor is not of concern as long as the minimum bed depth of 0.5-inch is maintained.
2. Configure a product setup for each type or color of powder with the following parameters:
...*Parenthetical entries refer to terminal wording where it differs from that of the Utility Software.
| ... | Set-up Number | Your choice |
| Set-up Name (Product Name) | Your choice | |
| Color Scale | L*a*b* | |
| Product Target Values (Target Values) | Establish using the read button with an ideal product standard, if desired (Enter values for ideal product standard, if desired) | |
| Chart Color Index (Display Height) | No (Yes) | |
| Hitch (Enable Hitch) | Off (No) | |
| Average | 1 | |
| Read Mode | Time Average (Time) | |
| Sample Time (Read Time) | 20 seconds | |
| Hold Time | 1 second | |
| Data Mode | Absolute | |
| Datalogging Interval | 1 second or more | |
| Background Distance | Recalculate for this product | |
| Cut-off Distance | Recalculate for this product | |
| Units (Height Units) | Your choice | |
| Alert Limit | Enter color values beyond which alert should be given | |
| Alarm Limit | Enter color values beyond which alarm state should be activated | |
| Analog Outputs (Channel Centers/Channel Spans) | If analog outputs available, enter appropriate values | |
| Filter | Enabled 0.50 | |
| Color Tracking (Track Color) | On and enter limits (thresholds) | |
| Tilt Angle | 0° | |
| Standardization Interval | If autocalibrator, available, enter appropriate choice | |
| AC Frequency | Enter appropriate value | |
| White Tile Values | Do not change values shown |
3. Begin the run.
4. Modify the target values and limits as necessary to optimize the process. The ideal situation is one where the reading of defective product immediately causes the alarm state to be activated, but acceptable product continues to be read as usual.