Use an oxalic acid solution to lighten dark stains on wooden surfaces and to remove ink stains from white wood furniture. Dissolve 28g/loz of oxalic acid crystals in 0.3 litres/| pint of hot water and, wearing protective gloves, rub the surface with a lint-free cloth dipped in the solution.
Continue until the stain is bleached out or the wood is bleached to the required finish. Finally, wipe the surface with vinegar, wash it thoroughly with clean water to counteract the acid and dry it. Store any excess solution out of the reach of children.