Wood bleach

[steambender]

The product I make requires me to steambend 11" to 16" wide boards, which are hard for me to find locally. I found a guy with a smaller sawmill in Wisconsin who gets urban logs and has shipped me a couple dozen 1/4" thick boards. The first batch I put on stickers and air dried, they turned out great. The second batch must have sat a bit too long before they were shipped and had mildew when they arrived. Hoping it was just on the surface, I stacked them on stickers and hoped for the best. After waiting 3-4 months for them to dry, I had them run through a wide belt sander down to my final thickness of 1/8". The mildew went all the way through on most of the boards. Would any type of wood bleach work on them? A darker stain would probably cover up the dark streaks, but I prefer a lighter stain. Luckily I only paid $1/bd foot and shipping wasn't too much. But I am hoping to salvage them. Any advice on the bleach?

 

[Roy G]

I had some luck with a bleach kit I got at Sherwin-williams. As I recall, it was two different bleaches that you use sequentially, up to two times depending on the stain to remove. It would lighten the stains somewhat, but never could quite remove it entirely. I was using it on an ash salad bowl, so your wood may react differently. It wasn't terribly expensive and I think you don't use copious amounts, so it goes a long way.

Roy G

 

[steambender]

Thanks. The boards I'm talking about are actually ash too.

The other thing I'm worried about is staining after hopefully getting rid of the mildew. I think fungus can actually change the structure of the wood so it absorbs the stain differently.

 

[Jeff]

How many board feet are contaminated? Your observation that the fungus is throughout the wood, and not just on the surface, suggests that it may be an exercise in futility. Thermal sterilization in a kiln would kill the fungus, but won't remove the tell tale signs of its presence.

Sherwin-Williams makes an oxalic acid based wood bleach, but it's probably only going to take care of the surface problem.

Wood Bleach

 

[Jim Wallace]

My reading on bleaching wood suggests three possible methods. Each one should be tried on a small sample. I am sure that none of these will work on anything but the surface (to the depth that they penetrate). That said, it the wood is only 1/4 inch thick and you treat both sides you may be close to treating the whole board. You could always cut into a piece shortly after treatment to see how far the liquid penetrates.

The first has been mentioned: oxalic acid. It's available at Home Depot etc. It usually comes as crystals that you mix with water. Apply it with a brush or sponge. Let it dry. See how much it's done.

The second is Chlorine bleach: Clorox. You can dilute it or not. Be careful breathing the fumes. Don't splash it on your clothes etc.

The third is Hydrogen Peroxide. There is an industrial peroxide bleach which is much stronger than what you get at the pharmacy to put on cuts etc. This is a strong bleach and may bleach out the grain of the wood as well as the fungus stains. I'm sorry I don't have a source for the industrial strength material.

Hope this helps.

Jim Wallace

 

[Jim Wallace]

I'm sorry, I mentioned that these bleaches are strong and should not contact anything but the wood you are trying to bleach, but I didn't actually mention that you should wear protective gloves when using any of these products.

 

[steambender]

I picked some of the bleach from Sherwin Williams today. I tried a little bit out on a scrap and wasn't impressed. I guess I will need to do several coats.

It is only about 30 board feet that was mildewed, but with the shipping and paying to have it sanded down to 1/8" I have about $100 in it.

There's also a little white rot on it. Although it's lighter in color, those white spots actually turned out darker when I put an alcohol dye on a scrap piece. That's my next hurdle. The only thing I can think of to keep the white rot from sopping up the stain more is applying shellac and avoiding stain entirely.

 

[Howard Acheson]

You are correct Jim, there are three bleaches used by woodworkers.

o Chlorine bleach (Fresh Clorox or swimming pool chlorine)-- use to remove or greatly lighten dye stain.

o Oxalic Acid--used to remove mineral and water stains from wood (black marks)

o Two Part A/B bleach(hydrogen peroxide/sodium hydroxide)--used to remove the natural color of wood.

For something like mildew, first treat the area with a chlorine bleach to kill the mildew. Then use the oxalic acid to remove most of the residual color. If however, the stain has gone all the way through the wood, it is unlikely that it can be removed.