Rx-Ry-Rz, Illuminant C, UV adjusted

This test is performed to determine the colour coordinates Rx, Ry and Rz of paper, solid board or folding board. Measurements of diffuse reflectance factor are used for the evaluation of optical properties such as diffuse blue reflectance factor (ISO brightness), the scattering coefficient of pulp, opacity, whiteness, luminous reflectance factor.

Operate the instrument in accordance with ISO 2469 and the manufacturer’s instructions.

Leave the samples exposed for 24 h to 23°C and 50% R.H., according to ISO 187.

Calibrate the instrument according to the instrument maker’s instructions, using a non-fluorescent ISO reference standard of level 3 (IR3). Adjust the UV-content to the C/2° Illuminant/observer.

Each sample pack is made of a pad of paper to be tested and a coloured cover sheet.

Remove the coloured protective sheet from the test piece pad.

Place the test piece in the position indicated on the cover sheet.

Without touching the test area, use the procedure appropriate to the instrument, to measure reflectance factor Rx, Ry, Rz of the top side of the test piece pad. Read and record the value. Move the measured test piece to the bottom of the pad and determine reflectance factor Rx, Ry, Rz for the next and similarly for the following test pieces, until at least ten test pieces has been measured.

Report 10 measures Rx, Ry and Rz in %, their mean and standard deviation calculated to 3 significant figures.