Painting info : Bleaching

 

Wood is usually bleached to remove old stains or to make the wood lighter so that one of the blonde finishes may be used. Floors, if left too long unfinished, will require bleaching to remove the stains in the wood. If the surface to be bleached has been painted or varnished, this finish must be removed in order that the bleaching agent can act upon the exposed wood and bleach out the stain that is in the grain.

Kinds of bleach

A bleaching chemical can be purchased ready-made, or a very effective one can be made by dissolving 1/2 lb. of oxalic acid crystals in 1/2 gal. of warm water. Oxalic acid may be purchased at hardware stores and is not expensive. This is an excellent bleach to use on large surfaces, such as floors, but on furniture it is generally easier to use a prepared brand of wood bleach. Needless to say, any chemical strong enough to bleach wood should be used with care, and steps should be taken to prevent its getting on hands, face, or in the eyes.

Using oxalic acid

In using an oxalic acid bleaching solution, brush the liquid on the wood while the water is still hot and allow it to remain there until dry. Several applications of the bleach may be necessary if the stain has penetrated deep into the grain. When the bleach is dry, a white powder will appear on the surface. If more bleaching is needed, apply an additional coat over the dry powder. When satisfactory results have been obtained, rinse the wood several times with fresh water to remove every trace of the acid. Add a small amount of vinegar to the final rinse to neutralize any remaining acid. It is very important that the wood be free of acid before any sanding is done. Oxalic acid is poisonous, and the fine dust of sanding which contains this acid can readily be inhaled. Sanding is necessary after bleaching, because the action of the water tends to raise the grain of the wood.

Other bleaches

Hydrogen peroxide can be used as a bleach for small spots, as can some of the chlorine solutions used for bleaching clothes.

 

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