Good Millwork. Used to make wood shingles, shutters, siding, and other exterior trim, TimberSIL Glass Wood is heat-treated in a patented process that infuses the wood with a soluble sodium-silicate solution to create a microscopic layer of amorphous glass within the wood — a permanent barrier against rot, termites, and other problems. The maker says TimberSIL wood remains nontoxic, odorless, nonvolatile, and will not corrode fasteners. It has a natural clear color and carries a 40-year warranty. 888.209.9307.