A wood preservative composition comprising 4,5-dichloro-2-octylisothiazol-3(2H)-one, a method of treating a wood substrate therewith, and a wood product produced therefrom are provided. The wood preservative composition comprises at least 0.5% by weight of DCOI based on the total weight of the composition and a retaining additive comprising a solvent-borne polymeric resin, a wax, or a combination thereof. A weight ratio of the DCOI to the retaining additive in the composition is in a range of 1:5 to 5:1.

An aqueous orthosilicate solution comprising m[SiO4.sup.4]+nX.sup.1+ in an aqueous solution wherein X is an alkali metal cation selected from the group consisting of sodium or potassium; and wherein n is four to five times greater than m. The aqueous orthosilicate solution is made by adding silicon particles of less than about 3 cm and water to a pressure vessel followed by adding a molar excess of alkali caustic to the pressure vessel containing the silicon particles. The temperature in the vessel is maintained not to exceed about 190 F. while an aqueous orthosilicate solution is formed. Upon cooling the formed aqueous orthosilicate solution is recovery. Aluminum or CuO can be added during the initial heating.