Gardner color scale

The Gardner Color Scale is a one-dimensional scale used to measure the shade of the color yellow.{{Cite web|title=The Gardner Scale: Modern Applications for Color Measurement of Transparent Liquids|url=http://support.hunterlab.com/hc/en-us/articles/360001215486|access-date=2020-09-04|website=Hunterlab|language=en-US}} The Gardner scale and the APHA/Pt-Co/Hazen Color Scale overlap, with the Gardner scale measuring higher concentrations of yellow color and the APHA scale measuring very low levels of yellow color.

History

Colors of transparent liquids have been studied visually since the medieval period.{{Cite web|url=https://www.sciencephoto.com/media/300104/view|title=Medieval urine wheel - Stock Image - N060/0108 - |website=Science Photo Library|accessdate=8 October 2023}} Changes in color can indicate contamination or impurities in the raw materials, process variations, or degradation of products over time.

One dimensional scales for yellowness were created, e.g., Gardner Color Scale and APHA/Pt-Co/Hazen Color Scale. The yellowness of the transparent liquid is determined by pouring the sample into a tube and comparing it to a pre determined and known standard. The standard that the sample falls closest to then becomes the value for the liquid. This procedure isn't extremely accurate due to variations of observers, illumination and to some extent the standards themselves.ASTM Paint and Coatings testing manual {{ISBN|0-8031-2060-5}}

Gardner Color can also be measured by a dual beam xenon flash spectrophotometer, for example the UltraScan Pro.{{cite web|url=https://www.hunterlab.com/media/documents/Supplemental_Manual_for_EZMQC_UltraScan_PRO.pdf|title=UltraScan® PRO Supplemental Manual for EasyMatch® QC|website=hunterlab.com|date=9 September 2019|access-date=8 October 2023}} Spectrophotometers measure the percent transmittance of the product and automatically calculate and provide the Gardner color number using illuminant C and 2º observer.{{Cite web|url=https://www.mt.com/ch/en/home/supportive_content/ana_chem_applications/uvvis/M9706.html|title=Gardner Color - UV Vis Spectroscopy|website=Mettler-Toledo International Inc|accessdate=8 October 2023}}

References

Category:Color scales