This method is mainly applicable to high gloss paper and paperboard such as cast-coated paper and waxed paper, and also to high gloss paper and paperboard printing samples, but not to coated or uncoated paper and paperboard with low gloss. GB 8941.1-1988 Paper and paperboard specular gloss determination method 20° angle determination method GB8941.1-1988 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Measurement of specular gloss (20°) for paper and board
20° angle measurement
Paper and board
Measurement of specular gloss (20°)This standard specifies the method for measuring the gloss of paper and board using a 20° angle gloss meter1 Scope of application
GB 8941.1-88
This method is mainly applicable to high-gloss paper and board such as cast-coated paper and waxed paper, and also to high-gloss printed paper and board samples, but not to coated or uncoated paper and board with lower gloss. 2 Definition
2.1 Gloss, the property of directional selective reflection on the surface of an object, which determines the degree of strong reflected light or mirror image of the object that can be seen on the surface of the object.
2.2 Specular gloss The ratio of the luminous flux reflected from the sample surface into the specified aperture in the direction of specular reflection (regular reflection) to the luminous flux reflected by the standard mirror under the same conditions, expressed as a percentage. 3 Instruments
3.1 The main characteristics of the instrument are shown in the appendix. Its optical system consists of a light source, a lens, a sample pressing plate and a photoelectric device. The positions and sizes of the main components are shown in Appendix A and the attached figure.
3.2 Gloss Standards
Theoretically, specular gloss The standard of glossiness is an ideal fully reflective flat mirror, and its glossiness value is set at 2037.6. According to this calculation, the glossiness value of polished black glass with a refractive index of 1.567 is given by the Fresnel formula as 100 glossiness units. 3.2.1 High gloss working standard The refractive index N of a smooth black glass plate is measured (the refractive index of the mercury e spectrum), and the glossiness value G of the working standard plate is calculated as follows.
3.2.2 Medium gloss standard plate
Z = arc sin sin20°
sin20°
Y arc sin.wwW.bzxz.Net
rsin*(20° -Z) + tg\(20° - Z)100
tga(20°+ z)
Isin2(20°+ Z)
sin*(20° -Y) + tg*(20° -Y))Lsin2(20°+Y) + tg2(20°+)
Objects with similar reflection characteristics to the paper sample under test, such as porcelain plates, can be used as medium gloss standard plates. The surface of the porcelain plate must be flat and the gloss must be uniform. Each porcelain plate must be calibrated with a black glass standard plate on an instrument that meets the requirements of (3.1) to calibrate the gloss value. 3.3 When not in use, the standard plate should be placed in a sealed box, kept clean, and prevented from contamination or damage to the surface. The working surface of the standard plate should not be placed downward to avoid dirt or wear. When holding the standard plate, hold it by the edge of the plate. To prevent the sweat on your hands from contaminating the working surface of the standard plate. The standard plate can be immersed in hot water and light detergent and gently scrubbed with a soft brush (not soapy water). Then rinse with hot water at nearly 65, rinse off the detergent, and finally rinse with distilled water, and put it in an oven at about 70C to dry. The black glass standard plate can be gently wiped clean with non-linting degreased lens paper or other absorbent materials, but the medium gloss standard plate should not be wiped. 3.4 As a high gloss standard black glass plate, after a few years, the surface refractive index will gradually decrease, and the gloss value will also change accordingly. Therefore, it is recommended that the test paper be calibrated by the superior metrology department once a year, and it is best to re-polish the surface to restore its original state. 3.5 Black cylinder with black velvet lining.
4 Preparation of samples
4.1 Samples are processed according to the provisions of GB450 "Taking of Paper and Paperboard Samples" and tested under standard conditions. 4.2 Avoid watermarks, spots and visible paper defects from the extracted paper sheets, and cut 5 test pieces of 100mm×100mm evenly along the horizontal paper width. Keep them clean and do not touch the test surface with your hands. 4.3 The glossiness of the sample will often be irreversibly reduced in a high humidity environment, so be careful not to make the sample damp. 5 Calibration of the instrument
5.1 Turn on the power according to the instrument manual. After preheating for the specified time, insert the black glass standard plate at the sample position and adjust the reading to the calibration value of the standard plate.
5.2 Replace the black stick and adjust the reading to zero.
5.3 Replace the black glass standard plate and recalibrate once, then replace the medium gloss standard plate and read the gloss value. The reading should be close to the calibration value of the standard plate. If the difference exceeds 1 gloss unit, check the geometry, spectrum and photometer characteristics of the instrument, or recheck the calibration values ​​of the two standard plates.
6 Test Procedure
6.1 After calibrating the instrument with the standard plate and black tube, insert a sample at a time and read the gloss value. Unless otherwise specified, the front and back of each sample need to be tested in both the longitudinal and transverse directions. During the test, the instrument can be repeatedly calibrated with the standard plate and black tube, and checked again after the test to ensure that the instrument is always calibrated correctly. 6.2 Take the average longitudinal and transverse values ​​of each side as the gloss value, and calculate the average and coefficient of variation of the gloss of the front and back of 5 samples respectively.
7 Accuracy
When measuring uniform samples with an instrument that strictly complies with this standard method, the reproducibility of the measurement results shall be within 2 gloss units. 8 Test report
Number of this standard;
b. Marking and description of the sample;
Gloss values ​​of the front and back sides, accurate to 1 gloss unit; Report the coefficient of variation of the test results as required; d.
Any test conditions that deviate from this standard.
GB8941.1-88
Appendix A
Provisions for 20° specular gloss tester for paper and paperboard (supplement)
A1 Dimensions and relative positions of main optical parts The distance from the light source filament to the illumination lens is 92mm, the illumination lens has a light-transmitting diameter of 37mm and a focal length of 63mm, and the distance to the center of the sample is 70mm. The diameter of the test hole is greater than 25mm, the diameter of the receiving hole is 11mm, and the distance from the center of the sample is 126mm. The focal length of the receiving lens is 47mm, and the distance from the receiving hole to the photoelectric device is 79mm. A2 Geometric conditions
The above dimensions can be modified to make the system meet the following geometric conditions: the angle of the incident light axis to the normal of the sample, i.e. the incident angle, is 20±1°. The receiving lens, the receiving hole adjacent to the lens and the optoelectronic device form a coaxial receiving system. If a plane mirror with a front reflection is inserted at the position of the sample, an image of the filament will be formed on the receiving hole. The diameter of the bright spot illuminated by the sample is not greater than one-fourth of the distance from the sample to the receiving hole. The receiving hole is star-shaped, and its diameter is 5° with respect to the center of the sample. The diameter of the filament image on the receiving hole is not greater than 2.5° and not less than 1° with respect to the center of the sample
A3 Reduce stray light
The interior of the instrument is painted with matte black paint, and the bulb, lens, optoelectronic device and the interior of the instrument should be kept clean and dust-free. A4 Spectral conditions
The spectral characteristics of the light source, filter and optoelectronic device as a whole should conform to the product of the spectral power distribution of the illuminant C and the CIE spectral light efficiency function. The deviation should be limited to a 500K change in the color temperature of the light source. A5 Photoelectric device
The photoelectric device and display circuit convert the received light flux into digital display. The conversion accuracy should be within 1% of the full range in the entire range. The receiving lens forms an image of the sample bright spot on the photoelectric device, and the image size should be greater than one-fourth of the total area of ​​the photoelectric device. A6 Sample pressing plate
The surface of the pressing plate should have no obvious stripes, be matte black, and have a flatness within 0.025mm. The pressing plate can open the suction switch while pressing the cardboard to form a negative pressure between the pressing plate and the paper sample, and suck the paper sample onto the pressing plate to keep it flat. A7 20° Angle Gloss Meter Schematic
Additional Notes:
GB8941.1-88
Receiving hole
Filter
Photoelectric device
This standard is under the jurisdiction of the Paper Industry Science Research Institute of the Ministry of Light Industry. This standard was drafted by Tianjin Paper Research Institute.
This standard refers to the American Pulp and Paper Association standard TappiT653os-76.448
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.