Q. Our customers like the white-colored, hickory sapwood lumber that we produce. The problem is that, especially in the summer, the sapwood is pink in color. Why is this?
A. The pinking discoloration is due to a chemical oxidation reaction in the wood that turns sugars and starches in the sapwood into this pink color.
This chemical oxidation reaction goes much faster when it is warmer, so we see the biggest problem in the summer. The reaction begins the moment a tree is cut down. Therefore, in summer we need to move very quickly from woods to sawmill to kiln.
The best color is obtained if we go directly into the kiln and if we use a fairly large depression or low humidity initially. That is, fast drying. Check page 75 in Drying Hardwood Lumber for the "white" hickory kiln schedule. Air flow must be brisk. The initial conditions in the first 24 hours are critical. Remember that it is not what you set but the actual conditions that matter.
Gene Wengert, “The Wood Doctor” has been training people in efficient use of wood for 35 years. He is extension specialist emeritus at the University of Wisconsin-Madison.
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