Utilizing Spectrophotometric Instrumentation in Plastic Production
Colorimeters have been used for decades in production and manufacturing, utilizing human eye technology to imitate color perception. However, this technology has now been replaced by more advanced spectrophotometric instrumentation. Outdated colorimetric technology only allows for pure color measurement and does not account for any changes in color perception due to variables such as texture, light source or viewing angle. Because molded plastic products come in a variety of shapes, textures and opacities, the requirements for color measurement extend beyond the capacity of rudimentary color data.
In the measurement of plastic materials, traditional transmission and reflected spectral data must extend to include yellowness, haze, gloss, texture, and other attributes to assure accurate color measurement. Newer technology also includes CIE L*a*b* color2 to fully maximize spectral measurement capabilities. Various sample types require different techniques for accurate color measurements, so understanding these techniques is the first step to utilizing your color measurement instrumentation.
A directional 45/0° geometry illuminates the sample at a 45° angle with the viewing angle set at 90°. Scientific studies show that these geometric principles provide the truest representation of visual color perception.3
Directional 45/0° geometry is ideal for opaque plastic measurement, where product samples are impenetrable by light and the desired results are to quantify a visually perceived color with a numerical value. However, both texture and gloss can present challenges in color measurement. In these cases, the best technique for obtaining an accurate measurement for color alone requires diffuse d/8° reflectance instrumentation. If a plastic sample is translucent in appearance, reflectance and transmittance measurements work best but may vary depending on the level of transparency. Transparent samples require transmission spectral instrumentation to achieve the most accurate results.