Q: I’m building a blanket chest and lining a portion of the inside with aromatic cedar strips. I realize that the aromatic cedar should not be finished, and I have been taught that none of the inside of the chest should be finished because the chemicals in the aromatic cedar will actually soften any finish. Is this still true or are there some newer products available that would be safe to use, particularly on the inside of the lid?
A: Aromatic cedar prevents the hardening of certain finishes, but not others. The ones it prevents from curing are oxygen polymerizing finishes. These include almost all oil-based finishes, such as varnish, polyurethane, Danish oil, teak oil and others. Non-oxygen polymerization curing finishes, such as automotive polyurethanes, and finishes that cure by solvent evaporation, work fine. Solvent evaporation curing finishes are shellac, lacquer and most water-based finishes.
For what it is worth, the curing problem is not the main reason why cedar-lined chests are left unfinished. Cedar emits a chemical that acts like naphthalene, the active ingredient in mothballs, which helps to repel moths. Thus, woolens can be kept safely in the chest. Furthermore, natural unfinished aromatic cedar imparts a very nice aroma to the clothing. Both the aroma and the moth-chasing properties are blocked if you finish the wood.