Color fastness and the concept of a gray scale

Color fastness is the ability to resist fading of textiles with the effect of a specific mechanical or chemical action. The poor color fastness of textile products is one of the main and common causes commonly complained by customers for the quality of clothing or textile materials in general, including fabrics and accessories zippers, embroidery threads, labels or neck bands, etc. The durability of a color may vary depending on the quality of the dye, the density, especially in the processes of bleaching, dyeing, finishing. all…. Color fastness also depends on the different types of impact on color fastness, for example a color may be resistant to dry cleaning, but less durable to water wash; Can be resistant to water or sweat but not to detergents, etc. The dye’s strength may also vary when exposed to different agents. Therefore, testing the durability of colors for any dyed or printed product is an extremely important issue for textile technology.

Textile materials, depending on different demands of use, may encounter different factors that influence the color fastness during their use. These agents may cause color or fading or staining to textile materials of different colors, pale or white upon contact with it, or fading by light. These different factors depend on the end use for which the products are designed. Factors that affect color fastness of textiles include light, water washing, dry cleaning, contact with water, sweat and detergents.

Common color fastness test standards applied to dyed or printed materials are as follows:

  • Color fastness to rubbing
  • Color fastness to wash
  • Color fastness to dry clean
  • Color fastness to light
  • Color fastness to water
  • Color fastness to perspiration
  • Color fastness is usually rated against two criteria
  • Change the color of the specimens before and after the test, called the color fade or color change.

The color of wires on other materials that are not dyed and exposed to the specimens during the test is color staining or color staining.
In order to assess by the number of degrees of color change and tint of the test sample, it is standardized to evaluate the test by comparing the results against a set of two standard gray scales, or called Gray scale. picture below:

– Gray scale for color change:
The gray ruler consists of ten pairs of gray numbered from 1 to 5. The number 5 has two identical grays, the number 1 shows the greatest contrast and numbers 2, 3 and 4 have intermediate contrast, The level of contrast increases from 5 to 1. Corresponds to the decreasing color fastness. After checking, the color sample will be compared with the original color sample (without test processing) and compared, based on the scale on this gray scale to evaluate. When there is no change in the color of the test sample from the original color, the sample will be classified as ‘5’ ie very good color fastness; similarly, the color change of the sample too much causes the same level of contrast as the number 1 gray pair, it will be assessed the level 1 color change, or the poor color fastness ….

 

– Gray scales for staining:

A set of different levels of white-gray pairs used to measure color temperature. The color string test sample from the test sample will be compared to a standard white sample (without color wiring exposure test) and based on this color scale to assess color fastness.

Durability rating of 5 is represented by two identical white patterns (that is, color wireless) and rank 1 for the highest distinct white and gray pattern (either too much string color or durability lowest color). The other numbers show that the contrast change between white and the gray standards increases from 5 to 1 or the gradation decreases from 5 to 1. If the result is between any two contrast levels, there is rating, for example, 3-4 or 2-3 or 3.5 or 2.5 …

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