ASTM D4890-18 Determination of Gardner and APHA Color of Polyols

ASTM D4890-18 describes test method A in which the color of the material to be tested is compared to a set of color standards that have been prepared in one of three prescribed ways and have specific chromaticity coordinates. The color of the item to be tested is compared to a series of platinum-cobalt color standards, which are indicated by mg of Pt/mL of standard solution in Test Method B.

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Scope:

The ASTM D4890-18 method is beneficial in determining the color of clear polyester and polyether liquids. Compared to other compounds, these methods are best applied to compounds with light absorption characteristics. They are suitable for research purposes, tests used for specification, and quality control areas. The most important specialty of these urethane compounds is their color.

Procedure:

In ASTM D4890-18, the tube is first filled with the sample, which should be free of solid particles. Next, the color of the sample was compared with the standard one. Then the color of the sample is reported in terms of the Gardner standard number that comes closest to it in terms of color. After that, the color number of the darker standard is reported if the sample appears to be exactly midway between the two standards. One of the two 100-mL tall-form Nessler tubes was filled with 100 ml of the sample for test method B. The Second tube is filled to the mark with the standard that, based on a preliminary estimate, appears to match the color of the sample. One may compare the sample’s colors and the standard by looking vertically down through the tubes against a white background. Subsequently, lighter or darker standards for the liquid in the second tube are substituted until an exact match is achieved.

Results:

The absolute difference between two individual ASTM D4890-18 test results obtained under reproducibility conditions is expected to occur with a probability of approximately 0.95 (95 %).