The color fastness results are divided into two parts: one is staining and the other is discoloration.
Staining depends on how much color of the sample is stained on the standard lining cloth, or how much color the lining cloth changes.
Discoloration is how much the sample itself changes color. The results will also be different depending on the lining and rating methods.
While correctly using the gray sample card of GB251-1995 for staining assessment, you must keep in mind the inherent color characteristics of the standard lining fabric when it is not stained.
For example, polyester lining is inherently brighter and has good gloss. The adhesive backing is reddish and slightly darker. Cotton lining is not as bright and white as polyester lining and has no obvious luster. The wool lining is yellowish and slightly less glossy. This is more conducive to clearly and accurately judging the staining degree of the lining fabric after the test. However, please note that the same backing fabric may have slightly different colors due to different batches. Failure to pay attention to the above issues may develop a bad rating vision, leading to errors in assessment results.
1. Use of gray sample cards.
The gray sample card used to evaluate discoloration in GB250-1995 and the gray sample card used in GB251-1995 to evaluate staining are both five levels and nine levels. There is no requirement for less than half a level. When observing a sample, the illumination of the light source is generally approximately 45 degrees to the surface of the sample, and the observation direction is close to perpendicular to the surface of the sample.
2. The impact of the cleanliness and actual status of the gray card on the accuracy and stability of the assessment results.
The cleanliness and actual condition of the gray card are very important to obtain accurate, stable and consistent test results. When using the gray card, the tester must not touch the nine pairs of gray/white small cards in the sample card. If the small card is found to be fluffed, scratched, damaged, or stained with water stains, stains, oil stains, color stains, or sweat stains, the tester should Discontinue use. When the sample card is twisted, distorted or uneven, use should also be stopped. In addition, the gray card will change during storage or use, and the chromaticity data at all levels and grades will deviate from the standard range. Pay attention to regular calibration and replacement. Otherwise, the accuracy and stability of the assessment results will be affected.
3. The impact of assessment sequence on rating results.
Color fastness inspectors have to evaluate large batches of samples of multiple colors every day, and the ratings will be biased due to different color light stimuli. It is recommended to cultivate the working habits of scientific eye and scientific grading, and choose a certain grading sequence according to the color of the sample. For example, when there are dark colors, light colors, oranges, and reds during the rating process, the light colors can be rated first, then the dark colors, then the oranges, and then the reds. To prevent eyes from being stimulated by colored light and causing errors in ratings. At the same time, after a batch of ratings, it is best to compare each pair of original samples and samples rated with the same grade number again and re-evaluate once. This provides a good indication of whether ratings are consistent. Any errors in ratings will be clearly visible at this time.
4. The impact of the lining method on the evaluation results.
(1) All fabrics and yarns should be stapled to the original recording paper and covered with clear tape on the tips of the staples on the back of the card for protection.
(2) In some places, double-sided tape is used for pasting, but using double-sided tape when pasting fabrics may cause the fabric to fade.
(3) Cutting: Trim the sides of the test sample neatly, leaving a large enough piece for rating. Nail the specimen to the card in a single layer, making sure that the nails are parallel to the short side of the specimen and as close to the edge as possible. Cut a piece of untested fabric of the same size and pin it on the card adjacent to the test sample. There should be no overlap or gaps between the two, and rate them.
When rating, ensure the following:
a) Ensure that the texture of the test sample and the untested sample are in the same direction (some warp knitted fabrics may have a less obvious texture).
b) For multi-color fabrics the different colors should be as close as possible. For example: striped fabric, stripes and color sequences should be in the same direction.
c) Thread and sewing thread: Both test and untested samples are rolled into a small bundle and stapled to the card.
d) The test sample is adjacent to the original sample.
e) Multi-fiber cloth: Trim the edges of the multi-fiber cloth neatly, leaving a piece as large as possible adjacent to the relevant test sample and pin it on the card. Make sure the heavily stained side is facing up and the staples are driven parallel to the short sides of the edges.
f) Cotton cloth for rubbing color fastness test: Trim the edges of the tested cotton cloth neatly. Because the staining rating is compared with the surrounding cotton cloth, the lining area should be as large as possible. In order to avoid wrinkles on the test sample and obtain poor results, the two sides of the cotton cloth must be nailed to the white card to give the cloth a slight tension.
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