Making Non-solid Samples Solid for Color Measurement - an12_07

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HunterLab often states that the ideal sample for yielding repeatable color measurements is completely opaque or completely transparent, flat, smooth, homogenous, non-directional, non-photochromic (not affected by light), non-thermochromic (not affected by heat), and non-hygrochromic (not affected by
moisture). What is not explicitly stated within this list is that the sample should also be solid. “What?” you may ask. “We measure liquid samples all the time.” This may be true, but you don’t measure a liquid sample directly or that liquid would damage the insides of the instrument. No, you pour a liquid sample into a sample cell or sample cup, which makes the surface presented to the instrument actually solid. There are several types of samples that require special techniques so that the sample is actually presented to the instrument as a solid surface.

Liquids
Transparent, translucent, and opaque liquids must all be placed in a container for measurement. Transparent samples would normally be placed in a glass transmission cell and measured in the transmission compartment of a diffuse/8° instrument such as the ColorQuest XE, ColorQuest XT, UltraScan PRO, or UltraScan VIS. Translucent and opaque liquids would either be placed in a glass sample cup and measured using a 45°/0° or 0°/45° instrument such as the LabScan XE, ColorFlex 45/0, or D25A (preferred) or placed in a glass transmission cell and measured at the reflectance port of a diffuse/8° instrument such as the ColorQuest XE, UltraScan PRO, or UltraScan VIS.

Semi-solids
Translucent semi-solids, such as yogurt, baby food, and salad dressings, would either be placed in a glass sample cup and measured using a 45°/0° or 0°/45° instrument such as the LabScan XE, ColorFlex 45/0, or D25A (preferred) or placed in a glass transmission cell and measured at the reflectance port of a diffuse/8° instrument such as the ColorQuest XE, UltraScan PRO, or UltraScan VIS.


Powders
While powders are technically solids, like liquids they would damage your instrument if not contained or made even more solid. Powders may be pressed smooth into a plaque and measured using a 45°/0° or 0°/45° instrument such as the LabScan XE or D25A in the port-down orientation or they may be placed in a glass sample cup and measured using a 45°/0° or 0°/45° instrument such as the LabScan XE, ColorFlex 45/0, or D25A in the port-up orientation. Less preferred, but still possible, is measuring powder in a glass transmission cell at the reflectance port of a diffuse/8° instrument such as the ColorQuest XE, UltraScan PRO, or UltraScan VIS.

Pellets
Plastic pellets and similar items like rice and sugar must be measured in a batch rather than individually, which makes them more fluid than solid. They would either be placed in a glass sample cup and measured using a 45°/0° or 0°/45° instrument such as the LabScan XE, ColorFlex 45/0, or D25A (preferred) or placed in a glass transmission cell and measured at the reflectance port of a diffuse/8°
instrument such as the ColorQuest XE, UltraScan PRO, or UltraScan VIS.

Large Particulates
Items larger than pellets, but that still must be measured in a batch, include things like cereal, dog food, and even small plastic parts. These items would either be placed in a glass sample cup or dish and measured using a 45°/0° or 0°/45° instrument such as the LabScan XE, ColorFlex 45/0, or D25LT (preferred) or placed in a glass transmission cell or Petri dish and measured at the reflectance port of a diffuse/8° instrument such as the ColorQuest XE, UltraScan PRO, or UltraScan VIS.

Textile Fibers
Like powders, textile fibers are technically solids. However, a transparent layer must be provided between the fibers and the sample port to keep the textile fibers in the proper place relative to the instrument optics, rather than having them enter the sample port. Normally, textile fibers are flattened to the bottom of a sample cup using the compression cell set available for the ColorQuest XE, LabScan XE, UltraScan PRO, and UltraScan VIS.

(See attached pdf file for the complete article with illustration)

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