Q: We have some yellow-poplar lumber that has a dark brown stain on the surface. It planes right off. What is it?

A: When you dry Y-P too slowly, the water inside the lumber moves to the surface, bringing with it various chemicals that have been dissolved in the water. When the water is evaporated, these chemicals are left behind on the surface.

Over time, a high concentration builds up on the surface. Unfortunately, these chemicals will oxidize and turn a dark brown color. If the wood is dried more quickly, then the water evaporates within the lumber, dispersing the color so it is not a problem. Cooler drying temperatures (130 degrees F maximum) at the initial stages of drying also help minimize the problem.