FAQ: “Appreciate any additional info you have on industrial standards used with road marking paints and especially thermoplastics.”
There are many physical attributes measured for road marking materials but the industrial test methods that are most often cited for measurement of daytime color for color specification of road marking thermoplastics are:
AASHTO M249-09-UL Standard Specification for White and Yellow Reflective Thermoplastic Striping Material
AASHTO - American Association of State Highway and Transportation Officials, Washington, DC USA www.aashto.org
ASTM D4960 Standard Test Method for Evaluation of Color of Thermoplastic Traffic Marking Materials
ASTM - American Society of Testing and Materials, West Conshohocken, PA USA www.astm.org
BS EN 1871 Road marking materials - Physical properties
BSI - British Standards Institute, London, UK www.bsi-global.com
Our preferred instrument for this application is a battery operated, portable MiniScan EZ 45/0 LAV for laboratory lot-to-lot QA and onsite field testing on a road surface, both at time of install and for in-service testing.
If the testing is strictly in the laboratory, the ColorFlex EZ, having the same optical path as the MiniScan EZ, would work as well.
Both MSEZ and CFEZ sensors measure directional reflectance of the marking best corresponding to visual evaluation. This is not retro-reflectance which requires an instrument with a specialized geometry.
While white and yellow are traditional colors, a bright orange is also being used around construction zones.
It is seldom that you would measure highway marking paints and plastics "wet".
The metrics measured are Y brightness or luminance (or Beta luminance factor) for C/2 conditions. In addition the x, y C/2 chromaticity values are typically plotted in an orthogonal tolerance plot for acceptance.
For laboratory applications, I have see the hot melt thermoplastic poured into a 150 mm diameter paint can lid, cooled to dry then measured. In all cases averaging multiple readings (suggest 3 or 4) per measurement in different areas of the sample is recommended.