ABSTRACT

The normal system as adopted in British Standard 1282 involves three main types of preservative. Type TO (tar-oil) comprises distillates of coal-tar including creosote. Type WB (water-borne) includes Wolman salts of the fluoride-chromium type and the copperchromium formulations which currently dominate this market. The boron diffusion process for green wood is also water-borne but is usually considered to be a special case, as is the use of aqueous solutions of sodium pentachlorophenate in sapstain control and aqueous emulsions of insecticides in Pinhole and Powder Post beetle control. Type OS (organic solvent) involves light petroleum solutions of pentachlorophenol, naphthenates of copper or zinc, chlorinated naphthalenes, organotin compounds and many other less important compounds including contact insecticides. In some areas such as

Scandinavia, many of the organic-solvent formulations are decorative and intermediate between a preservative and a paint but often achieving only l imited preservative effectiveness.