L*a*b* white paper, Illuminant D50, 45/0 geometry
Purpose of the test
This test is performed to determine the L*a*b* colour coördinates, using graphic arts spectrophotometers, of paper, solid board or folding board.
Procedure
Operate the instrument in accordance with ISO 13655 and the manufacturer’s instructions.
Leave the samples exposed for 24 h to 23°C and 50% R.H., according to ISO 187.
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 on a black backing.
Without touching the test area use the procedure appropriate to the instrument to obtain t L*, a* and b* coordinates.
Report 10 measures of L*, a* and b*, their mean and standard deviation calculated to 3 significant figures.
ISO 13655
Nr. of samples
10 test pieces per level
Sample size 100 x 200 mm²
Specil size A4
Levels
L*:
Level 1: 90.0÷92.0
Level 2: 95.0÷97.0
Level 3: 87.0÷90.0
Level 4: 90.0÷92.0
a*:
Level 1: -0.6÷-0.5
Level 2: -1.0÷1.0
Level 3: 0.0÷2.0
Level 4: 1.0÷4.0
b*:
Level 1: 10.0÷11.0
Level 2: 3.0÷-4.0
Level 3: -2.0÷1.0
Level 4: -12.5÷-6.0
Reporting
Report 10 measures of L*, a*, and b*, their mean and their standard deviation. All to three significant digits.