In the crockmeter test, the colorfastness ratings are determined by visually assessing the extent of color transfer or staining on the rubbing cloth or the standard fabric after the rubbing process. The evaluation is often done under standardized lighting conditions to ensure consistent and accurate observations.
Here are the general steps involved in determining the colorfastness ratings in the crockmeter test:
1. Prepare the specimens: Cut the test material and the rubbing cloth or standard fabric into standardized pieces of the same size and shape.
1. Mount the specimens: Secure the test material and the rubbing cloth or standard fabric onto the crockmeter instrument according to the manufacturer's instructions.
1. Perform the rubbing: Apply a specified load or pressure and a predetermined number of rubbing strokes between the test material and the rubbing cloth or standard fabric using the crockmeter. The rubbing may be performed in a straight line or in a back-and-forth motion, depending on the specific test method.
1. Assess the color transfer: After the rubbing process, visually evaluate the rubbing cloth or standard fabric for any color transfer or staining. The extent of color transfer is compared against the standardized colorfastness ratings provided by organizations such as the AATCC or ISO.
1. Assign the colorfastness rating: Based on the observed level of color transfer or staining, assign the appropriate colorfastness rating to the test material, such as excellent, very good, good, fair, or poor (as per the AATCC system) or grades 5 to 1 (in the ISO system).
It's important to note that specific test methods may have variations in the number of rubbing strokes, the load or pressure applied, and the criteria for assigning colorfastness ratings. These details are defined in the relevant industry standards or test protocols followed for the specific application or material being tested.