Solution No. 1



1 ounce potassium permanganate (other amounts may be used)

1 gallon water (distilled preferred)

Solution No. 2

3 ounces sodium bisulphite (4 ounces for strong bleach)

1 gallon water (distilled preferred)

Allow the mixture sufficient time for cooling before use. The permanganate solution should be applied very freely with a brush, setting all pocket tape measures, precision measurements tools, and your steel tape measure aside. If the wood is allowed to dry, it will have a slight purple tint, which will fade out with other bleaches. It is best, however, to apply Solution No. 2 before the first solution dries.

The sodium bisulphite solution seems to cause a bleaching out of all dark colored pigments and to produce whitening or bleaching of almost any wood, although the final tone or color varies with different woods.

The combination of an application of permanganate of potassium solution followed by a wash or coating of sodium bisulphite has proven to be a very powerful bleaching agent for wood. After you have achieved the desired color, it is best to sponge the wood with clean water to remove any excess of bleaching chemicals.

Sometimes a solution of sodium hyposulphite in a strength of 2 to 4 ounces to the gallon of hot water is substituted for the No. 2 solution of sodium bisulphite. The bleaching results of both of these chemicals are similar when used in a second solution. The hyposulphite should not be used without a previous treatment with potassium permanganate solution because it is ineffective.

Other Bleaching Agents

It is possible to bleach wood with several other chemicals which are mostly alkaline, or used with an alkali, or following the application of one. The best known and most affective of these bleaches are peroxide of hydrogen (H2O2) and lime bleaching powders. These alternative chemicals can be compared to using logger measure tapes or forestry tape measures instead of your usual pocket tape measures. Sometimes the final product will end up better than what you originally had in mind.

Hydrogen peroxide is an effective but rather expensive bleaching agent, which is sometimes used for small jobs and for bleaching stains. Before application of hydrogen peroxide a wash coat of ammonia or dilute sodium hydroxide should be placed on the wood. Then the bleaching agent, hydrogen peroxide, may be brushed onto the wood several times in full strength, if necessary, in order to obtain whiteness in the wood being treated.

The wood seems to darken, at first and then the dark-colored extract or pigment is bleached, possibly by oxidation of products soluble in water. If the hydrogen peroxide be fresh and strong, a 30% solution with water is often enough. It is best to wear rubber gloves and to wash off with water if any hydrogen peroxide comes in contact with the skin.

Bleaching powders produce whitening by a reaction of chlorine upon ordinary slacked lime when made into a thin paste with water. For walnut and some other woods, and especially for floors, this bleaching agent has been found to be quite satisfactory. The bleaching paste or solution must be mopped or brushed onto a floor promptly because the active chloride of lime is an unstable compound which decomposes rather quickly under ordinary conditions when it is moist or wet.

After bleaching, the chemicals should be sponged or mopped off with clean water in order to prevent any future bleaching or any unwanted reaction with the finishes. Also, set aside any expensive tools used in the bleaching process including unique tape measures or pocket tape measures to measure the wood being bleached. The ordinary bleaching powders of chloride of lime are wet with water, which brings about a chemical reaction that produces the active bleaching agent called calcium hvpochlorite (Ca(OCl)2) and also calcium chloride (CaCl2).

Very recently reports have come from chemical experimenters that, although calcium hvpochlorite is a good bleaching agent for wood and is easily obtainable from bleaching powders, they had found sodium hvpochlorite (XaOCl) in solution to be still better and that the last-named chemical left the surface of the wood in better condition for finishing than when you use calcium hvpochlorite made from bleaching powder.

When chloride of lime paste is used for bleaching floors and other wood surfaces, it should be mixed into a thin paste prior to application and cleaned off before it becomes quite dry. If further bleaching is needed, a No. 2 solution of sodium carbonate (Na2Co3) should be applied before the wood has become completely dry.

The No. 2 solution is made by placing a pound or a little more of the dry sodium carbonate salt into a gallon of hot water. Dust from sanding of bleached floors and other large surfaces is quite irritating if the finisher forgets to wear a dust mask or wet sponge over his nose.