WATER ABSORPTION of CORRUGATED BOARD – COBB 1800
Purpose of the test
This test is performed to determine the water absorption according to COBB, after 1800 s, of corrugated board.
Procedure
Operate the instrument in accordance with ISO 535 and the manufacturer’s instructions.
Leave the samples exposed for 24 h to 23°C and 50% R.H., according to ISO 187.
Weigh the dry test piece to the nearest 0,001 g.
Determine the water absorbency (Cobb value) of each of the test pieces using the standard method.
The water should be in contact with the surface of the test piece that is marked. Check that the water used is at the same temperature as the laboratory.
The total time between initial exposure to the water and final blotting should be 1800 s (30 minutes). The water should be poured off after 1785 s (29 minutes, 45 s).
The blotting paper should have a grammage of 225-275g/m2 and preferably a Klemm value of about 75mm.
Re-weigh the test piece to the nearest 0,001 g immediately after blotting.
Calculate the gain in moisture for each measurement and recalculate into g/m².
Report 6 measures in g/m², their mean and standard deviation calculated to 3 significant figures.
ISO 535
Nr. of samples
8 test pieces per level
Sample size 140 x 140 mm²
No special size
Levels
Level 1: 100÷130 g/m²
Reporting
Report 6 valid results of measurements in g/m², their mean and their standard deviation. All to three significant digits.