Gardner Color - UV Vis Spectroscopy

This application note provides experimental detail on how to determine the gardner color of different substances using a UV Vis spectrophotometer. Please proceed to download the PDF below to learn more.

What is gardner color?

It is a color system devised to provide a value of the yellowness of a sample and is often applied in production processes to assess the quality or aesthetic appeal of substances such as rosins, fatty acids, polymerized fatty acids, drying oils, varnishes and many other yellow/brown colored chemicals. Originally a method involving the visual comparison of the color of a sample to one of 18 standards, it has now been developed into a much more exact technique, providing an accurate result through the use of spectrophotometry.

The APHA color scale provides a way of testing colorless/ near colorless liquids and can often be combined with the Gardner scale for substances who’s color is between the scope of the two scales to provide an enhanced and even more accurate color measurement. 

ASTM, an international standards body have defined several procedures for testing the gardner color of samples, namely the regulation ASTM D1544: “Standard Test Method for Color of Transparent Liquids (Gardner Color Scale),” and ASTM D6166: “Standard Test Method for Color of Naval Stores & Related Products (Gardner Color Scale).” The procedure followed in this application note follows regulation set out by ASTM.

How can gardner color be measured?

A value for gardner color can be obtained accurately and efficiently using a UV/VIS spectrophotometer. The sample is placed in a cuvette, the measurement is quickly carried out using illuminant C and 2° observer. Then the percent transmittance is automatically measured and this result is converted to a numerical value between 1 and 18 which corresponds to value on the gardner color scale.

Using a METTLER TOLEDO UV/VIS Excellence spectrophotometer enables this method to be carried out using the predefined method on PC software LabX, which allows simple operation and automatic display of the gardner color number.