TAPPI T 412

Gravimetric Method

The test relies on a gravimetric process where a sample is weighed immediately upon collection to record its wet mass. It is then placed in a ventilated laboratory oven and dried for several hours to drive off all unbound water. The sample is transferred to a desiccator to cool before being weighed again to find its dry mass.

The difference between the two weights represents the moisture content of the board, which is expressed as a percentage of the original sample weight. This procedure must be executed quickly because dry paper absorbs water from the air, which would bias the results and distort the mill’s quality assurance data.

Quality Impact

Out-of-spec moisture levels can cause paperboard to warp, curl, or delaminate during the printing and converting processes. If the board is too dry, it can crack along score lines, while excess moisture can cause ink drying delays on the press. This testing ensures that paperboard sheets remain flat and stable throughout the entire production run.