The thickness of the coating film can be measured according to the method in the national standard GB/T9754-1118 "Paints and varnishes - Determination of 20°, 60° and 85° mirror gloss of paint films without metallic pigments". This standard is equivalent to the international standard IS02813-J978 "Paints and varnishes - Determination of 20°, 60° and 115° specular gloss of paint films without metallic pigments".
This standard specifies the method for measuring the specular gloss of paint films at geometric angles of 20°, 60°, and 85°.
The 60° method is suitable for all paint films, but for high gloss paints or near dull paints, the 20° or 85° rule is more suitable.
The 20° method can improve the sorting ability for high-gloss paints, and is suitable for paints with 60° gloss higher than 70 units.
The 85° method can improve the identification ability for low-gloss paints, and is suitable for paints with a 60° gloss lower than 30 units.
These methods are not suitable for the manual determination of the gloss of paints containing metallic pigments.
(1) Instrument
① Gloss meter, which is composed of a light source part and a receiving part. The light source passes through the lens so that the light speed is parallel or slightly convergent to the surface of the paint film of the test panel. The reflected light is converged by the lens of the receiving part, and absorbed by the light pool through the field of view diaphragm.
②Standard plate
(2) Test method
①At the beginning of each operation, first adjust the instrument and calibrate the gloss meter so that it can correctly read the gloss value of the high-gloss sample working standard plate, and then read the gloss value of the low-gloss-working standard plate. If the instrument reading of the low-gloss working standard plate differs from the specified value by more than 1 gloss unit, it is better to use it after readjustment by the instrument manufacturer. After using for a certain period of time, it is also necessary to calibrate the light buoyancy meter to ensure that the instrument works normally and stably.
②After the gloss meter is calibrated, take 3 readings at different positions where the surface of the test paint film is parallel to the coating direction, and then calibrate the instrument with a high-gloss working standard plate to ensure that the readings do not deviate. If the result error range is less than 5 units, then record its average value as the specular gloss value. Otherwise, make three quick measurements and record the average and limit values of all six numbers
③Using this method to measure gloss is meaningful only on paint films with good surface smoothness. Because if the substrate is slightly curved or locally uneven, it will seriously affect the measurement results.
