Q. We are having some issues with old growth western red cedar paneling. The wood is interfering with finishing. Any help?

A. Without being there, I can only guess, but I think I know the answer. When an old growth tree is growing, there is an anaerobic bacteria that often gets into the tree. It is in small compartments running vertically in the tree. While alive, it creates fatty acids that turn rancid with time. Did you or the homeowner mention any funny smell?

The bacteria also create some slime that tends to plug the moisture movement. The bacteria also somehow create very high moistures in the tree, as they are anaerobic. Finally, the bacteria create enzymes like pectinase that destroy some of the wood’s strength. I have seen discoloration in plastic overlaid molding...it comes through the plastic. The infected area is sometimes called wetwood or sinker stock. It often has a darker color.

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.