how to use gray card to test fabric colorfastness

As a textile lab researcher, do you know how to carry on a colorfastness gray card rating?

Colorfastness

Colored fabrics in the production and processing or clothing made of colored fabrics in the process of use will be subject to the force of various external environmental factors. The ability to resist this external force is called fabric or clothing colorfastness performance.

 Color change

In printed and dyed textiles, various environmental factors can cause color loss from the fiber, destruction of dye luminescent groups, or the generation of new luminescent groups, resulting in changes in color saturation, hue, and luminance.

 Color staining

It refers to the phenomenon where, under various environmental factors, dyes become detached from the originally attached fiber and transfer to other lining fabrics, resulting in the staining of the lining fabrics.

When doing colorfastness gray card rating, the colorfastness is evaluated using color-changing and staining gray cards. The gray card currently used are AATCC gray card, ISO gray card, JIS gray card, and China national standard GB gray card. Each gray card is slightly different in the grayscale.

Color-changing gray cards

stain gray card

Original grayscale vs. decreasing grayscale contrast card

5 grade 9 scale system; 5 grade is the best, 1 grade is the worst, and the middle can be rated half grade, such as 4-5 grade, 4 grade, 3-4 grade.

Stained gray cards

Original whiteness and grayscale increment contrast card

5 grade 9 scale system; 5 grade is the best, 1 grade is the worst, and the middle can be rated half grade, such as 4-5 grade, 4 grade, 3-4 grade.

Note: The above data are from

ISO 105 A02 gray sample card for color change evaluation

ISO 105 A03 gray sample card for color stain evaluation

colorfastness gray card rating method

rating grade form

Masking card

masking card

(In the above picture), during the rating process, utilize the masking sample card with specially designed small holes for assessing multi-fiber cloth staining, rubbing color fastness staining, and general staining assessments.

Using the masking card enables better focus on the sample being rated while covering other areas to prevent visual impact.

mask samples

During the rating process, splice the original sample with the sample to be graded, ensuring a minimal gap to avoid the color of the backing showing through and impacting vision. Use a masking card to mask around the original sample with the sample to be graded. Keep them on the same level as the grading gray card.

Grading Environment

 Light source

We commonly use D65 light source. The lamp life of the light source is 2000 hours. Other light sources can be specified, such as F light source, 84-P light source, UV light source, etc.

dark room lights

 Darkroom

The rating process requires conducting it in a dark room of constant humidity and temperature. Additionally, it is necessary to paint the dark room wall and its items in a neutral gray color, approximately matching the level between rating gray card level 1 and level 2 (approximately equivalent to Monsell color card N5). As shown above, the left is the neutral gray color of the wall when the light is on, and the right is after the light is off, requiring the entire darkroom not to have any other light source except the light source of the rating lightbox. And to ensure that no other debris shall appear on the grading table.

observer's line of sight

Grading Angle

Using gray cards for grading samples requires the correct angle of grading! The standard requires the sample to be at 45° to the horizontal, the rating light source to be at 45° to the sample, and the rater’s eyes to be at 90° to the sample. The distance between the eye and the sample is 50-70 cm.

Personnel requirements

  • The rating personnel is not color blind and can pass the color blindness test or Farnsworth-Munsell 100 color phase test.
  • Dress requirements: preferably gray clothes, no brightly colored clothing, no brightly colored nail polish, and any items that may reflect light sources.
  • Do not wear colored glasses.
  • Do not rate when you are tired or sick. Rating is a subjective act, and personal mood can affect the judgment of color.
  • The observer needs to acclimate under standard light conditions for at least 2 minutes before making observations. Allow the eyes to adjust to the current light environment.
  • Observer requires training and passing the test. Different personnel needs to carry out the same sample gaze calibration. To ensure that the error between personnel achieves the minimum, it is also necessary to carry out inter-laboratory gaze calibration work.

Colorfastness gray card rating is the display of color fastness test results, which is the last process of color fastness testing; no matter how accurate and standardized the previous process is, errors in the rating bring failures. The rating has always been difficult work. It is essential to ensure the consistency of the personnel in the same laboratories, and it is also essential to ensure consistency between the testing organizations. Consistency between the laboratories becomes important when more brands cooperate with more laboratories.

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