ASTM D1544 test method for color of transparent liquids (Gardner color scale)
4. Apparatus
4.1 Glass Standards, 18, numbered separately, and having the color characteristics given in Table 1. The color shall be produced by the glass components only. Some glass standards in use today do not conform to the values reported in Table 1. The calibration of glass standards should be verified prior to use, a suitable procedure for their calibration is contained in Appendix X1.
4.2 Glass Tubes, clear, 10.65 mm in inside diameter and about 114 mm in outside length. (Viscosity tubes, as described in Test Method D1545, are satisfactory.)
4.3 Suitable apparatus for comparing sample and standard. The apparatus may be of any design, but should have the following characteristics:
4.3.1 Illumination - CIE Illuminant C.
4.3.2 Surrounding Field - The field should not differ significantly in brightness from the samples and standards and should be essentially achromatic.
4.3.3 Field of View - The specimen and one or more standards should subtend a visual angle of about 2 ° and be in the field of view simultaneously.
4.3.4 Separation of Standard and Specimen - There should be a perceptible separation between specimen and standard, but this should be as small as is mechanically possible.
5. Procedure
5.1 Fill a glass tube with the material under test. If the material is perceptibly cloudy, first filter it.
5.2 Compare with glass standards, determining which standard most closely matches the specimen in brightness and saturation. Ignore hue differences.
