These are standard panels prepared by applying white emulsion paints on black scrub test panels. The films are indefinitely stable and the panels of each type essentially identical. They are used as controls in the measurement of scrub resistance, to obtain Calibration Ratings that normalize the wide variations often encountered for undefined reasons, among laboratories using the same scrub method. The Calibration Rating is the performance of the test paint panel expressed as a percentage relative to that of the selected Calibration Panel. Thus:
% Calibration Rating = Test Panel Cycles-to Failure/Calibration Panel Cycles-to-Failure x 100
The letter indicating the calibration panel type is appended to the calibration rating, e.g. 125A, 65C, 95D etc.
The figure to the left illustrates simultaneous side-by-side scrubbing of half-panels to maximize correlation, analogous to ASTM D 2486, Method B.
Note: ASTM D 4213 “Weight Loss Method” whereby:
Calibration Rating = Calibration Panel Weight Loss/Test Panel Weight Loss x 100