How do you check Cobb value of paper?

The Cobb/sizing is comes under the MISCELLANEOUS PROPERTIES.

If you do not want to use the old manual method. There do exists Automatic Cobb testers that also in addition to the static Cobb value for a given time, show you the dynamic Cobb value in a graph with time axis.

It is for example many times, more relevant to see the water uptake after ten seconds and not after one minute.