AATCC standards to determine the colorfastness of viscose yarns

To determine the colorfastness of viscose (a type of regenerated cellulose) yarns, the industry typically utilizes standardized methods developed by the American Association of Textile Chemists and Colorists (AATCC). As viscose is a cellulose-based fiber, its behavior is similar to cotton in many dyeing and testing contexts. Below are the primary AATCC test methods used to evaluate its colorfastness.

Important AATCC test methods for viscose yarns

• Colorfastness to Laundering (AATCC 61): This is an accelerated test that simulates the effects of multiple home or commercial laundering cycles. Since viscose can be sensitive to moisture and mechanical action, this test is critical for determining how the dye adheres under washing conditions.

Procedure: The yarn is typically knitted into a fabric specimen or attached to a white test fabric before being placed in a canister with a detergent solution and stainless steel balls for mechanical agitation.

• Colorfastness to Light (AATCC 16.3): Viscose fibers can be prone to fading when exposed to intense light. AATCC 16.3 uses a Xenon-arc lamp to simulate natural daylight or indoor lighting conditions.

Procedure: The yarn is exposed to controlled light, temperature, and humidity for a set duration. The degree of color change is then compared against a standard "blue wool" reference to assign a grade from 1 (severe fading) to 5 (no fading).

• Colorfastness to Rubbing/Crocking (AATCC 8): This test measures the resistance of the color to transfer from the yarn to another surface when rubbed.

Procedure: A standardized white test cloth is rubbed against the colored yarn in both a dry and a wet state. This is particularly important for viscose, which may lose some color during wet rubbing due to the fiber's high moisture regain and swelling properties.

• Colorfastness to Perspiration (AATCC 15): Because viscose is highly absorbent, it is frequently used in apparel that comes into direct contact with skin. This test assesses the color change and staining when the yarn is exposed to simulated acidic perspiration.

Important considerations for viscose yarns

• Sample Preparation: When testing yarn specifically, laboratories often use a knitting machine to convert the yarn into a small fabric swatch before testing. This provides a more uniform surface for color evaluation than testing loose, bundled, or skeined yarn. If knitting is not possible, the yarn may be wound tightly onto a template card, though this is less standard for certain types of wash tests.
• Evaluation: Results for all these tests are generally evaluated using the AATCC Gray Scale for Color Change or the AATCC Gray Scale for Staining. A higher grade (5) indicates excellent colorfastness, while a lower grade (1) indicates poor performance.

While AATCC standards are the benchmark for the American market, many international manufacturers also use the equivalent ISO 105 series (e.g., ISO 105-C06 for washing, ISO 105-B02 for light) for global compliance.

If you are setting up a testing protocol, it is recommended to consult the specific AATCC Technical Manual for the most current version of these standards, as testing requirements (such as detergent type, water grade, and exposure time) can vary based on the intended end-use of the product.