Iron, in the form of nails, hardware, or even bits of steel wool, often leaves a blackish stain on woods high in tannin, suc h as oak. A wash of oxalic solution removes these stains as well as the grayed color of oxidized wood.
Oxalic acid is sold in most hardware stores and home centers as a dry. white crystalline powder, fhe crystals arc toxic and irritating to mucous membranes, so wear goggles and a dust mask when handling the dry powder. In a glass or plastic container, dissolve an ounce of oxalic acid into a pint of warm water.
Make certain that you have removed all the offending metal before you bleach the wood. Sometimes stains are caused by broken-off nails or bits of fencing dial are hidden in the wood. Wet the surface with the oxalic acid mixture and let ii dry. Repeat il the stain is not completely gone. Once dry. sponge the wood with plenty of clean water to remove the crystalline residue. Any oxalic acid residue left in the wood will make irritating dust when you sand, so wear .1 dust mask and eye protection.
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