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GB 250-1995 English PDF (GB250-1995)

GB 250-1995 English PDF (GB250-1995)

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GB 250-1995: Gray scale for assessing change in colour

This standard specifies the gray scale for assessing the color change of textiles, in the color fastness test of textiles, as well as its application method. The precise color measurement interval value of this gray scale can be used, as a permanent record, for the comparison of newly produced gray scales AND the gray scales that have changed during storage or use.
GB 250-1995
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ISO 105/A02-1993
Replacing GB 250-84
Gray scale for assessing change in color
ISSUED ON: DECEMBER 08, 1995
IMPLEMENTED ON: MAY 01, 1996
Issued by: State Bureau of Technical Supervision
Table of Contents
1 Subject content and scope of application ... 3
2 Principles ... 3
Additional information ... 6
Gray scale for assessing change in color
This standard identically adopts the international standard ISO 105/A02-1993 "Textiles - Color fastness test - Gray scale for assessing change in color".
1 Subject content and scope of application
This standard specifies the gray scale for assessing the color change of textiles, in the color fastness test of textiles, as well as its application method. The precise color measurement interval value of this gray scale can be used, as a permanent record, for the comparison of newly produced gray scales AND the gray scales that have changed during storage or use.
2 Principles
2.1 The basic gray scale is composed of five pairs of matt gray small-cards (or cloth pieces), which are divided into five fastness grades, namely 5, 4, 3, 2, 1, according to the distinguishable color difference. Add half a grade in every two grades, namely 4-5, 3-4, 2-3, 1-2, to expand it into a five-grade nine-level gray scale. The first composition of each pair is neutral gray, in which only the second composition of color fastness grade 5 is consistent with the first composition; the second composition of other pairs becomes lighter in turn, BUT the color difference gradually increases. All levels of visual perception chromaticity are determined by chromaticity; the entire chromaticity is specified as follows.
2.2 Pieces of paper or cloth shall be of neutral gray color AND shall be measured using a spectrophotometer with specular reflection. Chromaticity data are calculated, using the Chromaticity system (10?? field of view) and D65 luminosity, in the CIE 1964 supplementary standard.
2.3 The tristimulus value Y of the first composition of each pair shall be 12 ?? 1. 2.4 The color difference, between each pair of the second composition and the first composition, is specified as follows:
The values in parentheses are only applicable to the 5-grade 9-level gray scale. 2.5 Use of gray scale: Place the original textile sample and the sample after test, side by side, on the same plane AND close to each other in the same direction. Place the gray scale close to the same plane. The background shall be a neutral gray color, approximately between grade 1 and 2 of this gray scale (similar to Munsey N5). To avoid the influence of the backing on the appearance of the textile, it may take two or more layers of the original cloth, as a backing under the original and after-test samples. In the northern hemisphere, it is illuminated with the northern sky light; in the southern hemisphere, it is illuminated with the southern sky light, or the equivalent light source of 600lx and above. The incident light is at an angle of about 45?? to the fabric surface. The viewing direction is roughly perpendicular to the fabric surface. Use the grade difference of this gray scale, to visually evaluate the color difference, between the original sample and the sample after the test.
If a 5-grade gray scale is used, when the color difference, between the original sample and the sample after the test, is equivalent to the visual color difference of a certain grade of gray scale, it is regarded as the color fastness grade of the test. When the color difference, between the test sample and the original sample, is in the middle of a certain two grades of the gray scale, it can be set as an intermediate grade, such as 4-5 or 2-3. Only when there is no visual color difference, between the sample after test and the original sample, can it be rated as grade 5.
If a 5-grade 9-level gray scale is used, when a certain grade of visual color difference is closest to the visual color difference of the original sample and the sample after test, it is used as the color fastness grade of the sample. Only when there is no visual color difference between the sample after test and the original sample, can it be rated as grade 5.
After a batch of samples is graded, each pair of original and post-test samples, which are graded at the same grade, shall be compared with each other. This will allow you to see, if the gradings are consistent, as any errors in the grading will stand out. If the color difference of a pair is inconsistent with other pairs in the same group, it shall be re- assessed against the gray scale; the originally evaluated fastness grade can be changed,

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