On the surface of the high-gloss coating, if there is a corrugated structure with a size of 0.1~10mm, there will be a light/dark pattern, which is called orange peel or micro-ripple. When light is focused on this plane, the contrast between bright and non-bright areas can be seen.
At a distance of about 3 m, long ripples are observed. At a distance of about 0.5 m, short ripples are observed.
The orange peel meter produced by BYK-Gardner (BYK-Gardner) is an instrument that focuses light on the surface and simulates vision to evaluate the orange peel of the coating. The instrument uses a laser point source to illuminate the sample (relevant instrument: lux meter). The instrument moves 10cm on the surface of the sample to scan the surface, the light source shines on the sample at an angle of 60°, and uses the same angle on the opposite side to measure the intensity of light reflected on the peak or trough and on the slope. According to the frequency of the signal and the test The relationship between the ripple frequency on the sample is used to measure the orange peel. The principle is shown in Figure 8-29.
On the high-gloss surface with a corrugated structure size between 0.1 and 30mm, the light-dark contrast phenomenon observed from the viewing angle is called orange peel and sagging. (Related instrument: Sag Tester) For a high-gloss surface with a corrugated structure size between 0.1 and 1mm, when the light reflected by the edge of the structure is strong and the contrast is obvious, it is called image clarity or brightness, contour Clarity, vividness.
When measuring orange peel, just move the instrument over 10cm on the coating film, and after hearing a sound, the measurement result will be displayed on the display window. There are two values: long wave L (structural size > 0.6mm) and short wave S (structural size < 0.6mm). The short wave reflects the influence of the roughness of the substrate, and the long wave reflects the leveling characteristics of the coating and the influence of the part structure. Figure 8-30 is the BYK_Gardner orange peel/image sharpness measuring instrument. (Related instruments: level meter, roughness Tester)
