The best advice you can receive about bleaching wood is to avoid it if at all possible. Of all the things that are done to wood furniture by amateurs and professionals alike, bleaching is probably the most dangerous to you personally and potentially the most harmful to the wood. Bleaching changes the chemical composition of the wood fiber in achieving its goal of changing the color and the process is never 100 percent reversible. The wood is just never quite the same.
A really good craftsman can sometimes return a piece of walnut or mahogany, for example, to a very good semblance of its original color, but there is always something missing to the practiced eye and as time goes by the “something” becomes more noticeable.
Bleaching is also especially hazardous to thin veneers. A couple of good rounds of bleach and neutralizer will dissolve the glue under thin veneer as well as eat away at the cellular structure of the veneer itself.
Having said all of that, however, there are times when there are no further options in lightening a piece of wood. Hard sanding has not evened out the color enough nor taken out enough old stain. Additional spot sanding is likely to cause swales and bellies and should be avoided. Even ironing has not removed enough of the old penetrating dye to suit you, so bleaching is what’s left.
There are several types of bleaches available to you including household liquid chlorine bleach (sodium hypochlorite), hydrogen peroxide, oxalic acid and two-part commercial preparations. All of these chemicals should be considered dangerous and all of them can be disregarded by the serious finisher except for the two-part commercial type.
• Chlorine bleach requires access to strong sunlight to be effective and that is not especially good for your antique. It also has a tendency to leave a high yellow or sometimes even a greenish tint to the wood.
• The type of hydrogen peroxide that must be used to have any effect is a much stronger solution than the 3 percent medicinal disinfectant in your bathroom. Stronger solutions that are used to bleach hair are usually required to do the job but results on wood may tend to be spotty and results are very moderate.
• Oxalic acid is powerful enough to do the job on the wood and on you. While it will not burn your skin terribly, it will burn your lungs if you breathe the crystals after they have dried. Oxalic acid is also fairly difficult to control and to achieve equalized results over a large surface.
• Two-part commercial bleach is the most reliable of the available options. It is effective and economical but must still be used with a great deal of care. The best version I have found is “WOOD BLEACH” by Kleen Strip. This is a two-part solution that is mixed in equal parts and applied directly.
|To carry out a bleaching project using two-part bleach you need the following:
* 2 PLASTIC buckets about 1 gallon size (NO METAL BUCKETS!)
* 1 “set up” of commercial bleach
* 1 quart of white vinegar
* 1 pair of goggles
* 1 pair of rubber gloves
* 1 long apron
* several disposable CLEAN WHITE rags approximately 1 foot square
* a work surface covered in old newspaper
Note that all bleaching is done on wood that has been stripped of all old finish, sanded with 120 to 150-grit sandpaper and wiped free of sanding dust. Don all your protective gear and prepare to work in a well-ventilated area. Mix parts “A” and “B” of the bleach in one of the plastic pails as per the product directions.
Mix the vinegar with an equal part of water in the other pail. Saturate a rag in the bleach solution and wring it out slightly in the pail before wiping uniformly on the piece of wood. Repeat the process several times, making sure all areas of the wood are equally wet. The bleach solution will start to foam when it works and gives you an indication of which areas may need more liquid. Reapply in those spots. Pay special attention to where the bleach is dripping. Make sure it is all contained on the work surface. Also make sure it does not run or streak on areas you do not wish to be bleached. Make sure it is not dripping on your feet. (You may laugh here but it won’t be funny in about 3 minutes.) Wipe up any errant bleach with a rag soaked in the vinegar solution and use such a rag to wipe splatters from yourself and the surrounding areas, frequently refreshing the rag in the vinegar.
Allow the bleach solution to remain on the wood surface for 5 to 15 minutes. You will begin to see a noticeable effect in that time. When the foaming action begins to subside, wipe down the entire bleached surface with a rag saturated in the vinegar solution to neutralize the bleach. This is very important not only to arrest the bleaching action but also because you do not want unneutralized bleach particles in the wood when you sand it. Do this several times, wringing out the rag in the vinegar each time. Wipe the piece of wood dry with a clean rag and allow it to air dry overnight. The bleaching effect will be greater tomorrow than what you see today. Make sure you have cleaned up runs and drips on the piece and place paper under it.
Rinse out all of your rags in the vinegar solution and then rinse them with clear water in the sink before placing outside to dry.
Rinse your gloved hands in the vinegar solution prior to removing the gloves. Pour the left over bleach solution into the vinegar bucket and rinse it out with some undiluted vinegar, pouring the excess into the vinegar bucket. Place the neutralized bleach/vinegar solution in the remaining bucket in the sun, outside for several days to evaporate.
After your piece has dried overnite, sand again lightly with 120 to 150-grit sandpaper and begin the finish process. If you are not satisfied with bleaching effect, re-do the process, but bear in mind that there are limits and some “character” marks and stains are usually acceptable. Good luck and work safely. ?
His book “How To Be a Furniture Detective” is available for $18.95 plus $3 S&H. Also available is Fred and Gail Taylor’s DVD, “Identification of Older & Antique Furniture,” ($17 + $3 S&H) and a bound compilation of the first 60 columns of “Common Sense Antiques by Fred Taylor” ($25 + $3 S&H). For more information call 800-387-6377, fax 352-563-2916 or firstname.lastname@example.org.
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