FAQ: "My client is looking for a source for testing lab for the Opacity testing of liquor. He is unable to send sample to his existing source in the U.S. Can you advise on this application?"
Liquor is typically a transparent liquid and can be highly chromatic. Usually we interpret "opacity with near-opaque materials measured in reflectance.
A counter interpretation for measuring "Opacity" of a chromatic, transparent liquid would typically be a Y% transmission D65/10 or C/2 value for the liquor sample measured at a defined cell path length.
The typical color quality concern being measured would be lot-to-lot consistency in the liquor product and it would be product specific.