1.   When wood absorbs moisture, its fibers swell.

2.   Crossgrain joints will not survive because wood absorbs and expels moisture with the change of seasons, winter generally being dry and summer being humid.

3.   Depending upon its sap and its density, some wood absorbs the solution in different amounts and will absorb to its own level of refusal.

4.   During the humid days of summer, the wood absorbs moisture from the air and the floor expands.

5.   Otherwise, the wood absorbs the moisture in the air and the grain swells, requiring you to sand again.

6.   This is not entirely true, and the unfinished wood will still absorb water.

7.   This usually happens in summer when the humidity is high and the wood absorbs it.