Color fastness (Colour fastness), also known as dye fastness, refers to the resistance of textile colors to various effects during processing and usage. The color fastness rating is evaluated based on the specimen’s color change and the staining of undyed adjacent fabrics. This article will discuss the AATCC 8 test method: color fastness to rocking.
What is the AATCC 8 method？
AATCC 8 is a testing standard used to determine the numerical amount of color transfer from the dyed or printed textile article such as a Knitted, Terry, or woven article.
We use a crockmeter (rubbing fastness tester) and white crocking cloth squares, both dry and wet (wetted with water) in this method. A colored (dyed or printed) test specimen is rubbed with a white crocking test cloth under controlled conditions (Temperature & Humidity). Color transferred from the colored specimen to the crocking cloth is evaluated by comparison with the AATCC referred Gray Scale for Staining (AATCC EP2), the AATCC 9-Step Chromatic Transference Scale (AATCC EP8), or by spectrophotometer of Degree of Staining (AATCC EP12), and a color fastness rating is assigned.
- For this testing method, we need the following:
- A crockmeter (Specimen holder for crockmeter & Spiral wire clip to fix the crocking cloth to rubbing finger);
- AATCC Crocking Cloth (50 ± 1 mm squares);
- AATCC 9-Step Chromatic Transference Scale (AATCC EP8);
- Gray Scale for Staining (AATCC EP2) ;
- White AATCC Textile Blotting Paper.
AATCC 8 Test Method
- Plug the cord into the Power supply and switch on the machine.
- Prepare the crocking cloth and specimen according to the required test method.
- Clamped the specimen at the base of the specimen mounting area with the help of the specimen holder.
- Set the cycles as described.
- Mount the test cloth on the rubbing finger with the help of a clip, and place the finger on the specimen.
- Press the “START” button to initiate the test.
- When the cycle counters count the selected number of strokes, lift the rubbing finger arm and hang it on its holder.
- Turn off the instrument and remove the specimen for evolution according to the test criteria.
Precaution and Tips on the AATCC 8 Test
- In case of damage or improper functioning of the machine, immediately stop the machine, inform the supervisor & put the “DO NOT OPERATE” board.
- Test Specimens: Use two specimens, one for dry crocking & the 2nd one for wet crocking.
If you want precise results, you can use additional specimens. Cut specimens are available for crocking of 50 × 130 mm (5×13 cm) and used for testing, preferably with the long dimension oblique to warp and filling or wales and courses (warp & weft). - You can use full width lab samples without cutting individual specimens, when multiple tests are needed and when using for production testing.
- If there is a possibility, any sample should be positioned obliquely. If oblique direction is not possible while testing, the report should mention it.
- To improve test accuracy, you should avoid raised areas such as seams.
- Samples should be prepared obliquely to the warp and weft or warp and weft.
Conditioning
Before testing, both testing specimens and the crocking cloth must be kept in specified humidity and temperature conditions as directed in ASTM D1776 (Method for conditioning) Standard Practice for Conditioning and Testing Textiles. As per ASTM D1776, the temperature should be 21 ± 2°C (70 ± 4°F), and the relative humidity should be 65 ± 5%. Keep each test specimen or crock square separately on a screen or perforated shelf of the conditioning rack.
Dry Crocking and Web Crocking Procedures
Dry Crocking Test
1. Keep the test specimen ( Woven, Terry, or Knitted sample ) on the base of the crockmeter, flat on the abrasive cloth, with its long dimension in the direction of rubbing.
2. Fix the test specimen holder over the testing sample and apply enough pressure to avoid slippage or wrinkling on the testing specimen.
3. The warp and weft directions should parallel the rubbing direction.
4. Fix the spiral wire clip on the rubbing finger to hold the rubbing cloth in place.
5. Position the clip with loops upward. (Don’t keep the loop point downward because there can be drag against the test specimen).
6. Set the program on DaRong crockmeter for 10 complete turns. Refer to each specification for any other required number of turns.
7. Remove the crocking cloth after the completion of 10 cycles, keep it in the conditioning rack, and then evaluate it as per the AATCC scale after the conditioning time.
Wet Crocking Test
1. First of all, weigh an entirely conditioned crocking cloth.
2. Calculate the required wet weight (65 ± 5% pickup) by multiplying the original dry weight (Before wetting the cloth) by 1.65.
3. Apply water evenly over the crocking cloth and again weigh to confirm the 65 ± 5% pickup as per testing SOP.
4. To get this pickup, use a syringe tube, a Dropper, and a graduated
pipet.
5. draw up water in mL to 0.65 times the weight of crocking.
6. After getting the required weight, lay a test specimen on the base of the crockmeter, flat on the abrasive cloth, with its long dimension in the direction of rubbing.
7. Keep the specimen holder over the specimen and apply enough pressure to avoid slippage or wrinkling.
8. Mount a crocking cloth square, the warp/ wales or weft/ course direction parallel to the rubbing direction.
9. Use the spiral wire clip to hold the square in place.
10. Position the clip with loops upward
11. Remove the crocking cloth after 10 cycles, keep it in the conditioning rack, and then evaluate it as per the AATCC scale after the conditioning time.
crockmeter track
crocking clothes
change after wet rocking
specification of crockmeterColor Fastness Rating
After completing the conditioning time as per ASTM D1776, remove nips from the crocking cloth for evaluation. Rate the amount of color transferred from the specimen to the crock square with the help of the preferred rating scale as per AATCC 8, AATCC Gray Scale for Staining (AATCC EP2), AATCC 9-points Color Transference Scale (AATCC EP8) or by spectrophotometer of Degree of Staining (AATCC EP12) and record the numerical rating. Average the individual results to the nearest 0.1 grade when multiple specimens are tested or when a panel of evaluators rate color transfer.
FAQs:
What is the AATCC 8 method?
This method evaluates the color transfer from dyed or printed textile surfaces on the other surface by rubbing.
What is crocking cloth?
Crocking cloth is made of cotton, which is used during crocking tests.
How do we improve color fastness to crocking?
We can improve color fastness to crocking by applying dye fixers during wet processing.
How to rate colorfastness?
There are AATCC scales to evaluate colorfastness ratings
Which instrument is used for crocking?
A crockmeter or A rubbing fastness tester is used for rocking.
Is a crocking test helpful for quality control?
We can evaluate how much color will be transferred from dyed textile material to other surfaces.
Related Resources
Insights to Colorfastness to Rubbing/Crocking Test
Crockmeter/Rubbing Colorfastness Tester
Test Procedure of Rubbing Fastness Test Using JIS Standard Crockmeter
AATCC 8/AATCC 165 Color Fastness Tester to Rubbing Y(B)571C
Mastering Color Fastness: Test Methods and Techniques for Exceptional Results