Bleaching Wood

Discussion in 'Tutorials and Tips' started by Bill Boehme, Jul 26, 2016.

  1. Bill Boehme

    Bill Boehme Administrator Staff Member

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    This tutorial is about bleaching the natural color in wood and not bleaching mildew, weathering, and other stains in wood. Bleaches made for removing the natural color in wood consists of strong concentrations of two separate chemicals -- sodium hydroxide (lye) and hydrogen peroxide (about 30% which is ten times stronger than the stuff found drugstores). The foundation for my tutorial is based on this old article on the US Forest Products Laboratory web site. It is worth reading to get a basic understanding about bleaching wood. This tutorial puts the basic theory into practical application based on where I have found the chemicals and how I have used them and my results.

    I want to emphasize that using two-part wood bleach involves the use of very strong chemicals that produce strong exothermic reactions (release a large amount of energy, sometimes violently if not handled properly. Improper or careless use can result in serious burns and blindness. While I describe safety precautions and protective equipment, that doesn't constitute sufficient understanding and background information. Anybody without sufficient training in chemical safely shouldn't use these procedures to bleach wood. Even if you believe that you have adequate training, you assume all risks.

    My reason for bleaching was to be able to use dyes on figured maple without contending with the color shift resulting from the additive combination of the dye color with the wood color. That problem is most apparent with blue and purple dyes, but red and green hues. Are also affected.

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    Making Your Own Two Part Wood Bleach

    THIS PROCEDURE DESCRIBES MIXING AND USING CHEMICALS THAT ARE HAZARDOUS TO YOUR HEALTH IF THEY GET ON YOUR SKIN OR IN YOUR EYES. USE OF THESE CHEMICALS IN THE MANNER DESCRIBED HEREIN IS AT YOUR OWN RISK.

    Since two-part wood bleach seems to have all but completely disappeared from the market, I did some Internet searching and found on the Forest Products Laboratory website that sodium hydroxide (ordinary lye or drain cleaner) plus hydrogen peroxide is the only bleach that will remove the natural pigment in wood. Not all wood can be bleached, but it works well on many domestic hardwoods and softwoods. Don’t expect it to work on most oily tropical hardwoods. I tested it on some very dark redwood and it bleached it to a very pale tan in the earlywood and a medium to dark tan in the latewood.

    I use Chestnut dyes on figured maple primarily and my reason for bleaching as most of us already know is to minimize color shift. While we think of maple and ash as being white, but in reality they have a very strong yellow content. This means that if you apply blue to the wood you wind up with blue + yellow = green. Same thing when you apply red dye the result is more like orange. I have also bleached flame box elder and the result is really dramatic. By removing the yellow, the color of the red goes from orange-red to a brighter looking magenta-red. I have been extremely well pleased with the Chestnut dye on bleached maple. So far, the colors have stayed bright and true. Years ago, I used TransTint dyes and while the initial results looked good, they very quickly faded to pale drab colors even though indoors in low light.

    The drain cleaner lye must be the really cheap stuff that consists only of sodium hydroxide crystals (which are pure white) If you use some of the more expensive fancier ones that claim "great foaming action" or other such stuff then that is the wrong product because they contain other metal like magnesium to make them fizz and foam. They will also have a light gray or blue color and may look more like flakes. A one-pound container is about $5 and if you mix 182 grams (6.4 oz.) in a gallon of distilled water it will produce the right concentration for part "A" of a two part bleach.

    The hydrogen peroxide you need is not the stuff that you find at the pharmacy which is only 3%. What you need is the much stronger variety that is approximately ten times as strong. After doing a bunch of searching I found that there are two products that are commonly available, Baquacil Oxidizer and Aqua Silk Shock Oxidizer ... both are swimming pool chemicals. The cost is about $20 for a one-gallon jug. The concentration of hydrogen peroxide for both of these products is 27% which is just perfect for part "B". There are a number of different shock oxidizer chemicals on the market and most contain chlorine in one form or another and most definitely MUST NOT BE USED especially not mixed with a strong base like sodium hydroxide.

    I bought the sodium hydroxide from my neighborhood Ace hardware store and then found the Aqua Silk Oxidizer at a pool store on the way back home. And, I then stopped at the Walmart Neighborhood Market to get a gallon of distilled water for less than a dollar. So, for $26 I was all set to have a gallon each of part A and B with enough sodium hydroxide left to make nearly two more gallons in the future. This appears to be roughly a tenth the cost of the Zinsser Wood Bleach. In later looking at the MSDS plus other searching I verified that what I made is the same concentrations that the Zinsser Wood Bleach product consists of. BTW, it is also useful to have either some white vinegar or a solution of oxalic acid on hand to neutralize the wood once done.

    Dealing with strong caustic chemicals is very hazardous. If you are one of those who think that safety is for sissies then this procedure is definitely not something that you should try because you will suffer some very serious injuries. As a minimum wear goggles plus face shield, industrial long rubber gloves, long sleeved clothing, and a rubber lab apron is probably also a good idea. This applies to all phases of mixing up the sodium hydroxide solution and using the chemicals on wood. Also wear rubber boots and do all of your work outdoors in mild weather. Have a water hose with a spray nozzle handy because it will be needed even if it is only to wash down the wood after the bleaching is done. For storage, I recommend two five gallon plastic buckets ... the kind that you find at the big box stores or the used pickle buckets that you can get at Firehouse Subs (my favorite). Store each gallon jug in a separate bucket and keep them in a cool place (a hot garage or shop doesn't qualify as a cool location). The purpose of the bucket is to catch the spill if the container ruptures -- this safety tip comes to you courtesy of my own personal experience of not using a bucket. Sodium hydroxide will do a number on a concrete floor.

    There is only one right way to mix sodium hydroxide with water ... all of the other ways are very-very wrong and dangerous. NEVER EVER ADD WATER TO THE SODIUM HYDROXIDE OR ELSE IT WILL EXPLODE INTO YOUR FACE. Start with the full volume of water and very slowly add small amounts of sodium hydroxide to the water while gently stirring. Add only a tiny amount and allow enough time for the solution to cool down before adding another tiny amount. Doing this over a 30 minute period for a one gallon solution should keep it from getting too warm. A lot of thermal energy is released in the process. Do not use a metal container and many types of plastic such as PET or PETE are softened or partially dissolved. A glass container is ideal. I have a gallon jug that I use.

    Now that you are ready to start, put on your safety gear and set up everything outdoors. I get two measuring cups (plastic or glass will do, but not metal) and pour a little of part A into one and part B into the other. Then I carefully pour part A (sodium hydroxide) all over the wood and if necessary use a small plastic paint brush to quickly spread it around. Work fast because it will start foaming as soon as it hits the wood. Then I very quickly pour part B (hydrogen peroxide) on the wood and use the brush if necessary. I let it sit for a few minutes, but I don't let it sit long enough to start drying out. I usually give it about three or four minutes before I get the sprayer and hose it down. If you wish, you can use vinegar or oxalic acid to help neutralize the surface at this point. Then do a final rinse and quickly dry with a towel and sit it in the sun to dry for a few hours. Once the wood is completely dry you can do the final touch-up sanding to remove raised grain. If you don't already know this, the wood needs to be completely finished turning and sanded before bleaching because the bleaching only takes place on the surface and anything more than light sanding will set you all the way back to square one.

    I want to also mention that the method of application that I have described is what works best for my needs. There are various different methods that others have used such as mixing the chemicals before applying them to the wood or letting the sodium hydroxide dry before adding the hydrogen peroxide. There aren't any rules that are set in stone so see what works best for you. I will add some photos in the (hopefully) near future.

    One final note ... If you turn flame box elder, bleaching the wood gives especially beautiful results if you want to emphasize the red color. Because of the yellowish tan of the wood, the red normally has an orange-red color. After bleaching the wood has a snow white color and the red goes from orange-red to a bright nearly magenta-red.
     
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  2. hockenbery

    hockenbery AAW Advisor Staff Member

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    Great discription of the products and use of the bleach.
    Timely too as the bleach is now hard to find and your product list saves a lot of $$$$.

    Another source for additional information is the article by Gary Guenther in the February 2013 American Woodworker.

    Gary mixes the two parts before applying.
    I mix the two parts when using kleanstrip It has always worked well and is one step painting vs 2.
    I let the piece dry completely after painting with the bleach and sometimes do a second coat.
    I don't rinse or neutralize.
    When dry I hand sand the raised grain wearing gloves and a respirator and apply a finish.
     
  3. Bill Boehme

    Bill Boehme Administrator Staff Member

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    I took a look at the article and I was amazed at the similarity to what I had learned. I would say that he copied me ... three years before I wrote up what I had learned. :D

    Now I feel foolish for posting the tutorial.
     
  4. hockenbery

    hockenbery AAW Advisor Staff Member

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    To me it reinforces the do it yourself model.
    Great minds coming up with the similar recipes.
    Plus we need more online info in the tips section.
     
  5. Mark Hepburn

    Mark Hepburn

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    Hey Bill, I agree with Al.

    nothing to be ashamed of here. You provided a much easier way to get at the information. I did go to the archives and printed out those pages (50 and 51, Feb 2013) but with your post, I copy / paste and have a word doc or pdf that I can put on my shop ipad for future use.

    Great stuff, thanks!

    Mark
     
  6. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Mark and others, if you printed out my tutorial I found that I didn't proofread carefully enough. In the paragraph where I describe putting the bleaching chemicals on the wood, I called both A and B hydrogen peroxide. I corrected the description to say chemical A is sodium hydroxide and chemical B is hydrogen peroxide. Sheesh, I need to get my "lyes" straight. :D Next thing you know, I'll be saying hydrogen hydroxide. :eek:
     
  7. Mark Hepburn

    Mark Hepburn

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    Bill, I never would have called you a Lye-r.

    Oxygen Oxide to you sir! Oxygen oxide, I say!+

    So now I have to Cut / Paste / and save all over again. That took nearly 8 seconds...

    :D
     
  8. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Sounds like a lot of rusty air to me. Well, hydrogen hydroxide is just so much water under the bridge. :p:D

    We might need to add hip waders to the list of safety gear. :)
     
  9. Mark Hepburn

    Mark Hepburn

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    and olfactory protection for readers of this thread. :D
     
  10. Steve Worcester

    Steve Worcester Admin Emeritus

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    @Bill Boehme , you might want to put that into a PDF and attach it to the post
     

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