A.Weathering stains can usually be removed by bleaching with a solution of one pound of oxalic acid crystals dissolved in a gallon of warm water. This bleach may be applied with a cloth swab, brush, or sponge, then rinsed off thoroughly with warm water after the stains disappear. The bleached area will probably have to be refinished, and matching the original finish can be difficult. Prevention, of course, is the best solution.
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