To properly calibrate a color fastness rubbing tester, follow these steps:

1. Make sure the rubbing tester is clean and free from any debris or residue from previous tests.

2. Place a calibration fabric or rubbing cloth of known color fastness in the test area. The calibration fabric should have a standardized level of color fastness to serve as a reference.

3. Adjust the test conditions to the desired settings, such as speed, pressure, and number of rubs. Consult the test instrument's user manual or relevant standards to determine the appropriate settings.

4. Start the rubbing test and perform the required number of rubs on the calibration fabric.

5. After completing the rubbing test, remove the calibration fabric from the tester.

6. Evaluate the color change or transfer on the calibration fabric against a standardized color scale or rating system. This will help determine if the tester is calibrated accurately or if any adjustments are necessary.

7. If the results deviate from the expected color fastness rating, consult the instrument's user manual to make any necessary adjustments or calibration settings. This may involve adjusting the pressure, speed, or other parameters to ensure accurate and consistent test results.

8. Repeat the calibration process periodically or whenever there are significant changes to the testing conditions or equipment to maintain accurate calibration.

By following these steps, you can properly calibrate a color fastness rubbing tester and ensure reliable and consistent test results.