Background: In heartwood it occurs only in the first and last forms. Wood that is thoroughly air-dried retains 8–16% of the water in the cell walls, and none, or practically none, in the other forms. Even oven-dried wood retains a small percentage of moisture, but for all except chemical purposes, may be considered absolutely dry.
Question: What does wood retain in its cell walls despite being air-dried?
Answer:<extra_id_0>.
<extra_id_0> water<extra_id_1>