OptLab-SPX   Gardner Color Scale

As well as the Pt-Co/APHA/Hazen color scale, the Gardner scale also aims to estimate the color of yellow to brownish liquids. The application area of his scale is mainly binding agents and thickeners for paints. The procedure for visual inspection is described in ISO/DIS 4630-1 (Draft 2002). OptLab-SPX uses the procedure as described by ISO/DIS 4630-2 (Draft 2002), which describes an objective procedure based on the sample spectrum.

The color scale uses 8 solutions of potassium-hexachloroplatinate(IV) and 10 solutions of Co(II)Cl2/Fe(III)Cl3 as stronger colored references. The norm reproduces the color coordinates for all 18 reference solutions and describes an algorithm to determine the Gardner color value from these and the xyY color coordinates of a sample. The result is the Gardner color value with one fractional digit. The integer and fractional digits are derived in two separate steps. The resulting Gardner color value is the sum of the two sections.

When the sample color deviates substantially from the color of the similar reference, the fractional digit calculation may give a value above or below the expected range of 0 - 1. The norm does not give advice for such a case.

The additional OptLab-SPX parameter Gardner color check will test the level of the fractional digit result. If the range is within 0 – 1, the message “Sample is within color scale” will be output. Other wise the message “Sample is outside color scale” will be given. Thus the user has an option to estimate the color deviation of the sample.

Another calculation parameter allows comparing the result of Gardner color value to a given limit. The output is given as a text.

OptLab-SPX outputs the Gardner color value as a figure and a check value for color deviations. It also allows comparing both values to a specified value. Header, messages and number format can be defined. Thus all necessary options for a routine usage are available.