How to Measure the Color of Tinted Glass
Early glass was not colorless; it was naturally tinted due to abundant impurities in raw materials, which caused coloration. Later, glass manufacturing evolved toward higher light transmittance, lighter hue and lower impurity content. With social progress, glass development has become diversified, and tinted glass is widely demanded. Especially in recent decades, tinted glass has gained great popularity.
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Tinted glass offers various practical uses. It absorbs specific visible spectral bands to soften sunlight, eliminate glare and improve indoor chromatic atmosphere. It effectively absorbs solar radiant heat to achieve the cold-room effect for thermal insulation and energy saving. Besides, it strongly filters ultraviolet rays to prevent indoor articles from fading and deterioration, and delivers excellent decorative effects for buildings.
After years of development, measurement methods for glass color have gradually matured. The transmitted and reflected colors of architectural glass are measured using the spectrophotometric colorimetry, i.e., a method that determines the tristimulus values and chromaticity coordinates by measuring the spectral reflectance or spectral transmittance of the object being tested.
The measuring geometric condition for spectral transmittance is 0°/0°. The included angle between the optical axis of the illuminating beam/receiving beam and the sample surface normal shall not be greater than 10°. The angle between the optical axes of the illuminating beam and receiving beam shall not be greater than 3°.For at least one of the beams (illuminating or receiving), the angle between any light ray and its own optical axis shall not be greater than 5°.
The measuring geometric condition for spectral reflectance is 8°:8°, while those for off-angle spectral reflectance are 30°:30°, 45°:45° and 60°:60°. The deviation of the incident angle of the illuminating beam and the acceptance angle of the receiving beam shall not be greater than 1°. Under normal reflection measuring geometric condition, the angle between any ray in the illuminating or receiving beam and its optical axis shall not be greater than 5°. Under off-angle reflection measuring geometric condition, such angle shall not be greater than 2°.
Based on the measured spectral transmittance and spectral reflectance, under the condition of CIE standard illuminant D65, calculate the tristimulus values X10, Y10, Z10 of the sample color in the CIE 1964 standard colorimetric system. Then convert X10, Y10, Z10 via the CIE 1976 uniform color space conversion formula to obtain the color space coordinates L*, a*, b*, which represent the transmission color and reflection color of the tested sample.
In accordance with the above color measurement principles, color measurement can be performed on body tinted glass, solar control coated glass, Low-E glass, as well as glass with both body tinting and coating tinting. Such measuring instruments are already available on the market. Herein, three professional glass color measuring instruments developed by Aoptek Scientific are recommended.
This instrument is a practical and fast measuring instrument specially developed for the glass industry. It can measure optical parameters of monolithic glass as well asinsulating glass without damaging its structure, and quickly obtain transmission & reflection color coordinates and color difference values of glass directly.
GlasSpec1000 can measure the overall direct spectral transmittance and spectral reflectance without destroying insulating glass structure. With dedicated software function, it can directly obtain the color parameters of monolithic glass and insulating glass.
Filmeasure2200 Off-angle Spectrum Reflectance Instrument (Wavelength range: 380nm~1000nm)
The Filmeasure2200 is used to measure the spectral reflectance, reflection color coordinates and color difference of coated glass at the special angle of 45° or 60° , which is necessary for the double silver/triple silver Low-E glass, because such Low-E glasses are prone to color difference at these off-angles.
