ECONOMIC WOODS OF THE UNITED STATES 65 



Color adds greatly to the value of wood for interior finish, 

 cabinet work, marquetry, and parquetry. It is a very common 

 practice to stain wood artificially. Light-colored and therefore 

 less valuable wood of mahogany, such as commonly grows in the 

 United States and Mexico, is often darkened; Ilex opaca is readily 

 stained black to resemble ebony; Betula lenta, when properly 

 stained, is a good imitation of mahogany; in fact, by the applica- 

 tion of stains and finishes the variations in color and shade that 

 can be produced in woods is practically unlimited. It is also 

 possible by the introduction of certain chemicals to color the 

 sapwood of a living tree. 



For some uses of wood lack of color is prized. This is especially 

 true of pulpwood, since coloring matter, if present, must be 

 bleached out. Color is also undesirable in certain grades of 

 flooring. In handles and spokes dark color is considered a defect, 

 since it indicates heartwood, which is usually (but erroneously) 

 thought to be weaker than the colorless sapwood. 



All woods darken upon exposure to the atmosphere, probably 

 due to the oxidation of the coloring matters. The rich golden 

 yellow of Toxylon and Morus becomes a dark or russet brown; 

 the sapwood of Alnus oregona turns reddish brown; Pinus monti- 

 cola and P. strobus -often become vinous red, especially near the 

 end of an exposed piece of wood. On this account the natural 

 color of a wood can only be seen on fresh-cut sections. Prolonged 

 immersion in water causes wood to darken — some turning gray, 

 others almost black. 



Some woods {e.g., Cladrastis lutea, Prosopis, Sequoia, Juglans) 

 impart color to water in which they are soaked. The color of 

 many others can be removed by treatment with NaOH or other 

 chemicals, but it is often necessary to reduce the wood to pulp 

 before it can be bleached. Many tropical woods {e.g., Clorophora 

 tinctoria, Hoematoxylon campechianum, Ccesalpina, Pterocarpus) 

 contain coloring principles of value in the arts for dyeing, though 

 they have been largely superseded by aniline dyes. Of indigenous 

 woods, Toxylon pomiferum and several species of Xanthoxylum 

 are sometimes employed for this purpose, usually as adulterants 

 of old fustic {Clorophora). 



Color is often of great assistance for diagnostic purposes, 



though the range of variation and difficulty of description must 



always be taken into consideration. Unless otherwise stated, the 



colors mentioned in the key refer always to the fresh cross section 



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