The moisture given off by wet wood, especially freshly cut wood, is seldom neutral in reaction; it is probably never alkaline. In the great majority of species it is, in fact, acidic. Among the acids definitely identified as having been evolved from wood are carbonic, formic and acetic, but the freshly cut boards of many species are frequently characterized by the distinctive odors of highly fatty acids, of alcohols and esters. In addition to the volatile substances produced in wood by fermentation after felling, many oils which are volatile in water vapor are produced in the normal metabolism of trees. The well known oil of turpentine which is present in several of the common softwoods may be mentioned in this connection. The volatile substances given off by wood may have a solvent action on certain types of coatings. English oak is one of the worst offenders.