Plastic Plaque Color Measurement

Plastic plaques are thermoplastic materials compression molded into test specimens for the purpose of color measurement according to ASTM standard practices, and also used as product samples representing a plastic manufacturer’s color palette. For over 60 years, major plastics manufacturers around the world have relied on the knowledge and expertise of HunterLab to help them maintain color consistency throughout their supply chain.

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Lot-to-lot or piece-to-piece color consistency is an important indicator of quality for many plastic items. The process of pressing a plaque for the purpose of color measurement is commonplace in plastics processing, with well-established ASTM guidelines for best practices. Plastic plaques can range from opaque to translucent or transparent, so require different measurement techniques depending on the sample type.


Opaque Plaques are impenetrable by light and are best measured using a Directional 45°/0° reflectance instrument or a Diffuse d/8° reflectance instrument:


  • – If you are measuring opaque plaques and desire to quantify a numeric value to visual perception, then the proper measurement technique is to employ a directional 45/0° reflectance instrument. This is the geometry that most closely matches how the human eye sees color.
  • – If you are measuring opaque plaques and desire to negate the gloss and texture components of the sample and look at color only, then the proper technique is to employ a Diffuse d/8° reflectance instrument.


Translucent Plaques allow light to pass through, but only diffusely, so that objects on the other side cannot be clearly distinguished. Both reflective and transmittance measurement modes may work well depending on the translucency of the sample.  As a rule of thumb,


  • – If at the path length that your customer will view the sample, you can see slight details of your thumb or finger through the plaque, then transmittance is the preferred measurement method.
  • – If you cannot see slight details, then reflectance is preferred.
  • – Path length is defined as the thickness of the sample from where the light enters to where it exits the sample.


Transparent Plaques allow light to pass through with little or no interruption or distortion so that objects on the other side can be clearly seen. These plaques can only be measured using transmission instrumentation.


Additionally, certain metrics and indices such as CIE L*a*b* Color, Whiteness, Yellowness and Haze require the use of specific geometries and specific measurement modes. For the proper instrument selection for your application please refer to the following HunterLab Solutions Chart.

Many HunterLab spectrophotometers have the versatility to accommodate most applications of color measurement, however, based on 60+ years of experience and a thorough understanding of our customers’ needs and product use, these particular instruments are most suited for this industry application:










UltraScan VIS (Diffuse d/8° sphere Geometry, Reflectance, and Transmittance, 360-780 nm)

30% of our customers select this instrument for its extended wavelength measurement and its ability to measure both reflected and transmitted color of samples that are transparent to opaque.

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NEW Vista spectrophotometer with the unique ability to capture both visible range transmission color and haze with a single measurement is a replacement for ColorQuest XT.

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