Attempts to Modify the Weathering of Redwood

There seems to be increasing public awareness of the limitations of clear film-forming finishes in exterior applications on redwood. The most desirable natural finish, then, is none at all. However, during the stages of weathering, uneven discolorations often appear. Several methods of obtaining attractive, “unfinished” exteriors were studied: 1) Chemical modifications to inhibit mildew growth and prevent migration of extractives to the surface; 2) solvent seasoning, again to deplete surface extractives, and inhibit mildew growth; and 3) use of water-repellent preservatives to retard moisture pick-up and inhibit fungal growth. The latter method appears best so far because of easy maintenance, low cost, and natural appearance. Even so, the treatment must be repeated periodically, and the blackish discoloration from iron contamination may result if the finish is not stored and handled carefully.

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