AS NZS 1301.545:2018 Methods of test for pulp and paper
8.1 If the sample contains or may contain a fluorescent whitening agent, check that the 420 nm UV- cut-off filter is in the UVex(420) position.
8.2 Remove the protecting sheets from the test-piece pad. Without touching the test area, use the procedure appropriate to the instrument and the working standard to measure the intrinsic luminance factor R y,∞ of the top side of the test-piece pad. Read and record the value to the nearest 0,01 % of the luminance factor.
8.3 Remove the top test piece from the pad and, with the black cavity backing the test piece, measure the single-sheet luminance factor, R y,0 , for the same area of the test piece. Read and record the value to the nearest 0,01 % of the luminance factor. 8.2 and 8.3 describe the two independent measurements required to calculate the light absorption and scattering coefficients using the Kubelka-Munk theory in Clause 9. This is not intended to imply that the two measurements shall necessarily be made in this order.
8.4 Move the measured test piece to the bottom of the pad. Repeat the measurements of R y,∞ and R y,0 , moving the top test piece to the bottom of the pad after each pair of measurements, until five pairs of measurements have been made.
This subclause implies that measurements of R y,∞ and R y,0 shall be made alternately, but this is not an essential requirement of this document. The five measurements of R y,0 may be made before or after the five measurements of R y,∞ if such a procedure is preferred, or the measurements may be made alternately.
For greater accuracy, if the grammage of each individual test piece is known, calculate s y and k y for each pair of measurements and then calculate the mean values.
Calculate these values to the nearest 0,1 m 2 /kg for each set of measurements. Report the light- scattering coefficient to the nearest whole number. If the light-scattering coefficients for the two sides of the sample do not differ by more than 1,0 m 2 /kg, report the overall average. If the two sides differ by more than 1,0 m 2 /kg, report the average value for each side separately. Similarly, report the light- absorption coefficient to the nearest 0,1 m 2 /kg.