Comparison Protocol
Visual assessment protocol for determining the magnitude of color change in textiles after exposure to testing stresses or environmental factors through comparative grey scale analysis. The aatcc ep1 procedure defines a standard method for grading the difference in color between an untested specimen and a treated sample using a scale of five paired grey chips. This classification system allows laboratories to assign a numerical value to the fading or staining observed after laundering, light exposure, or crocking tests.
It establishes the baseline for all colorfastness reporting in commercial textile trade. The protocol requires specific lighting conditions to ensure that the human eye perceives the contrast correctly without interference from external glare or shadowed areas.
Visual Methodology
Lighting requirements for this assessment typically specify a d65 daylight simulator to maintain consistency across different global testing facilities. Technicians place the specimen alongside the grey scale and evaluate the contrast between the original and tested fabric against the contrast shown on the scale steps. Visual evaluation of aatcc ep1 depends on the optical acuity of the operator and the strict adherence to the geometry of viewing, usually at a forty five degree angle.
Standardized surroundings are maintained by using a neutral grey viewing cabinet to prevent color spill from walls or clothing. The procedure identifies whether the color shift is a change in hue, value, or chroma.
Grade Assignment
Numerical grades range from five, indicating no change, down to one, which represents a heavy loss of color or a shift in shade. A grade of four represents a minor contrast that is usually acceptable in most retail garments, while a three is the minimum threshold for performance apparel. The aatcc ep1 scale uses half grade increments to provide more granularity in the report.
Each step on the scale corresponds to a specific color difference measured in cielab units, providing a bridge between human perception and instrumental measurement. Accurate grading ensures that a mill can verify if the dyeing process meets the fastness requirements specified in the purchase order. When multiple observers evaluate the same sample, their results are averaged to minimize individual bias.
This averaging process increases the reliability of the final grade assigned to a production lot.
Acceptance Threshold
Commercial contracts cite these grades as a pass or fail criterion for bulk shipments of finished goods. If a fabric fails to meet the grade specified in the technical data sheet, the aatcc ep1 result triggers a claim or a request for reprocessing. Manufacturers use these results to adjust dye recipes or finishing chemicals to improve the bond between the pigment and the fiber.
The boundary of the test is visual, it does not provide the chemical reason for the failure but rather the physical evidence of it. Successful implementation of this procedure reduces the risk of consumer returns due to fading. Quality control teams rely on these grades to maintain brand consistency across multiple production sites and fiber types.
Results are recorded in a permanent quality log to track the performance of specific dye houses over time.
