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Bleaching wood


Janel

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A question from Cornel Schneider, and one that I have as well:

 

I have a question : Do You know a technique with wich I can bleach boxwood? Is there a chemical-solution or something else to do it ? There is no problem to colour the wood in every direction, but to bleach it ? ......to give a more white touch?

 

Thanks for any tips

 

Janel

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Guest DFogg

I bought some wood bleach a while ago. It comes dry and you mix it. I think it is used for old floors primarily and boy was it strong. It sucked the color right out of the wood. I can't remember where I found it, but it was local either a hardware store or feed store.

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We were a little late weather-proofing our deck. We bought bleach at the grocery store and used it straight. Did not mix it at all. It took all the weathering out (gray) out of the pine boards. It would probably work on boxwood. Try a small piece, by its self. Hope this helps.

Make sure you rinse the wood with water, after the bleach,Grin. I almost forgot that. :)

 

Chuck

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Cornel wrote that he has used two liquid chemicals:

 

...two liquid chemical substances. The first is " Ammoniak 25% ", the second is " Wasserstoffperoxyd 30% ".

First, I make the wood wet with Ammoniak, then the same procedure with Wasserstoffperoxyd. I must repeat the procedure again and again, until the colour bleaches".

 

The chemicals are Ammonia and Peroxide

 

He wrote this morning that the procedure worked "...and the result is superb. Now, the piece of wood looks like a real bone. I am happy about the result."

 

I am curious about the piece he did this to!

 

Has anyone else used these materials to bleach wood?

 

Janel

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I'm always a little cautious when it comes to the subject of bleaching. I have the need to bleach paper now and again with the paper restoration I do to pay the mortgage. Bleaches can be very powerful. By this I mean that they can continue to be reactive after you think you've rinsed the item completely. Color reversion (back to the original pre-bleach color) can also occur. They can also 'burn' and cause material loss.

 

Bleaches can fall under the categories of being either oxidative or reductive. the difference is the route by which they do what they do.

Hydrogen peroxide (H2O2) is an oxidative bleach. It will reach an end point in its bleaching and the by-products are water and oxygen so it seems like a good choice to use. Color reversion can be a problem at times. A bleach like Sodium borohydride (Na(BH4)2) is reductive. This may have some use in bleaching boxwood also. It would have to be ordered from a chemical supply house and needs refridgeration and some other safety precautions but I think it would be effective.

I'd stay away from anything with chlorine in it (laundry bleach, Chlorox, sodium hypochlorite, etc) for health reasons and the fact that it keeps on working (albeit with diminishing returns). A chemical called an anti-chlor is needed to stop the reaction.

 

Like the discussion of tagua nuts, I think it comes down to a choice we make as artists- are we concerned only about the appearance and chemical state of the item at the point when someone acquires it, or do we try to do as much as possible to prolong its life. I suppose it's somewhere in-between for most of us :D

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well, ammonia seems to have an effect when oxidatively bleaching of helping things along. I think it must have something to do with changing the pH of the bleaching to alkaline.I'll leave it at that :D We do some light bleaching (leaving paper in the sun, or in water tanks with daylight fluorescents) and a few drops of ammonia to the bath gives better results. It's anecdotal in the conservation community. I don't recall reading any studies of the actual chemistry going on.

It may help also in washing out discolored byproducts of the bleaching reaction,cutting through wood oils, etc giving better results.

 

Hydrogen peroxide can be found in pharmacies at 3% but also 30%. Sometimes the concentration is listed in 'vols' but that gets a little tricky. What works at 30% will work at 3%, just more slowly.

 

25% ammoniak. I'm guessing that was ammonium hydroxide (NH3OH) which you can get full strength (I'm not sure what conc. household ammonia is sold at). Even diluting it down to 25% with water will still wake you up out of the deepest hangover. I wouldn't think he even needs that much. Even 5% will do. Without rambling too much, but since you asked ;) , it's all about pH. Cornel probably only needs the pH around 10 or so. 25% will still be off the scale at 14. He ought to be able to find some pH detection strips at a garden shop or a Chemists- they always seem to stock more fun stuff at European pharmacies! ;)

 

Hope that helps :)

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Just in to my email from Peter Welsh:

 

Hi Janel,

 

Just a quick note, re: bleaching wood. Feel free to pass it on to Cornel. You should be able to find a 2-part kit for bleaching wood. The usual components are: Part A, Sodium Hydroxide, Part B, strong Hydrogen Peroxide. Part A is applied first, and before it is dry, Use Part B. The reaction will 'fizz' and should be repeated (A followed by :D as often as necessary. The reaction is stopped by flushing with water. (you should not mix the 2 chemicals together. The reaction time is fast and would render the mix ineffective) It is difficult to control accurately ( patchy). This mix is useful to bleach out a carving to allow a more even staining. As far as I recall, French Polishers use this mix, before restoring colour to furniture. There should be something on the 'net, butI don't have time to look at present. It may well be possible to use the ammonia as Part A, as Cornel suggests. I just can't recall that chemical being used with peroxide.

 

Some of the other chemicals used in bleaching wood are not effective for anything other than removing stains, etc.

 

Regards,

Peter

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sodium hydroxide is of course lye, so it is very caustic. Please wear gloves. It's the active component in many drain cleaners.

It looks like then that alkalinity IS important with hydrogen peroxide bleaching. Both ammonia and NaOH are strongly alkaline.

 

Thanks for Peter's message

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  • 8 months later...

I noticed a forum member Ed (Firewoodstudio) has a number of bleached basswood carvings on his website.

Ed, would you be willing to share your methods of bleaching? What bleach(es) do you use, how do you apply them? Have you noticed any longer term changes/darkening/reversion of color?

 

Thanks,

Doug

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I will be glad to share. I used parks wood bleach. It is the same 2 part bleach talked about by others. I got mine at a home center like Lowes, Home Depot, and from a local paint store. I found that you need 2 throw away 1" brushes and 2 plastic cups, to put equal parts, A in one, B in the other. You take part A, and wet the piece completely, It flows like water so wet the piece so it looks the same all over. Then you let the piece set for I think it is about 10 min. instructions on package. This is when I washed out the brush for part A. With the brush for part B you do the same, With Basswood you will see it start to change. Make sure you cover the piece completely. Then set aside and let dry. For about 12 hrs. On basswood the bleach will leave it covered with like a fine salt or sandy feel. This will sand off easy I used 240 then 400 grit paper. Then I use Clear Briwax and burnish the wax with a good old used cotton rag. That has wax built up, I rub till I feel the heat. The piece comes out looking like bone or marble depending on the grain pattern. The bleach will discolor you skin Wear protection or like I do use scrape pieces of wood to move the piece. :)

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I use the same kind of two part bleach and apply it just like firewoodstudio describes. I find it takes 3 to 5 applications to bleach boxwood really white - probably because it is so dense, it takes a while to penetrate deep enough. Of course, the two bleach parts are in aqueous solution, so the wood grain gets raised. You shouldn't plan on carving after the bleach application since you'll carve through the white layer quickly and expose the raw, unbleached boxwood beneath.

 

post-11-1137641295.jpg

Here are a few images of a little sparrow netsuke I did a while back, from my old camera so I'll apologize for the quality (lack of). I've adjusted the colors as best I can to approximate the actual colors. On the left is raw boxwood (the actual piece for this carving), center is the carved and bleached sparrow, and on the right is the finished, with linseed oil finish. I used the white boxwood as a canvas for Procion dyes and woodburning. You can see the white wood uncolored and unburned on the head and throat of the finished sparrow.

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