ASTM D4890 Polyurethane Raw Materials: Determination of Gardner and APHA Color of Polyols
The color of polyols and lubricating oils may indicate the degree of refinement or the presence of contaminants (including soot, oxidation products and packing debris) . This test determines the color of fluids using either the APHA Color Scale or the Gardner Color Scale. The APHA Color scale (Platinum/Cobalt Color Scale or the Hazen Color Scale) measures the color of transparent liquids, differentiating between shades of pale yellow in nearly colorless samples. The scale runs from 0 to 500 hundred with 0 being distilled water. The Gardner Color Scale also differentiates between shades of yellow, but it measures a wider range of colors to include red-yellows and green yellows. It runs from 0 to 18 with 0 being distilled water and 18 being a dark, murky yellow. A 500 on the APHA Color Scale corresponds to a 2 on the Gardner Color Scale.
Colored standard solutions are prepared. The sample is placed in the test container and compared to standards. The color of the standard that most closely matches the sample is reported. Please specify Method A (Gardner Color) or Method B (APHA Color).