My beams were exposed to the weather for a few weeks and some have developed some dark stains (mold, I'm guessing?). It's mostly on the sapwood areas and the heartwood looks fine.
How should I clean this?
I was thinking a bleach solution might work but I wasn't sure if it would harm the wood.
I don't want to stain them but prefer to leave it natural.
Anyone have any suggestions?
Jdhen they make regular wood bleach or re-newer but a solution of I think "Oxalic acid" but I would double check around will bleach the darker stains out. Here is a site of different ones.
http://www.google.com/search?q=wood+bleach&rls=com.microsoft:en-us:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7GGIE_en
Jdhen I was wrong on the earlier post of the acid. I modified it to reflect the correct one. So this is just in case you had alredy read it. By modifing my original post it would not re-post the corrected info therefore that is why I re-posted.
I agree with John, a wood bleach, deck brightener or deck cleaner that contains oxalic acid is what I use, it'll generally remove black nail stains as well. Sanding is the best. If none of that works and if it is just in the sapwood then you have bluestain, or sapstain, same fungi, different names. It is a non decay fungi that feeds on the sugars in the cell lumen, the hollow center, but doesn't eat the cellulose of the cell wall. Unfortunately if that is it, it is nonremoveable. Call it denim pine and learn to love it. I've tried everything and have talked to more than a few experts, it's there. Doesn't hurt anything but you are seeing it's hyphae inside the cell. So if it's on the surface, it should be easy to remove chemically or manually, if it's deep, you're stuck with it.
If it's blue stain keep in mind that some people pay extra for wood like that. Really, they do.
I have an issue with some of my beams as well. They are hemlock beams. Would I use oxalic acid on this spot as well. Not really sure what it is? ???
(https://i275.photobucket.com/albums/jj317/kubes14001/beam.jpg)
It will probably work, that looks like it could be a stain from a green timber on a forklift fork. Could also be a dirty strap or bolster. Once you start clean the entire beam to avoid a spot. That would also sand out. Once you start sand the entire beam to avoid a spot. That blue streak in the floorboard is the bluestain we were talking about above.
well, the timbers were purchased and installed "green" and my older photos indicate that the stain was on there then. I'll have to get some of that stuff and try it out!
John, I had a lot of trouble finding any wood "bleach" product. The big box stores both said they had discontinued it and I went to 4 lumber stores and got the same cross eyed look from them when I asked for it. I finally found some at a small lumber yard. Since the purchase I've come across several websites that suggest buying oxalic acid crystals and mixing a few ounces of it with a gallon of warm water. I think this would be a more economical way of doing it. The product I bought was not expensive at $12 but it only covers a small amount of the area I need to clean.
http://www.woodfinishsupply.com/OxalicAcid.html this is the recipe
http://www.rockler.com/product.cfm?page=19462&source=googleps oxalic acid crystals
How did it work? Do you have any before and after pictures?
Haven't used it yet but I will soon and I'll post some pictures when I do. My stains are much worse than yours.
Ok...I look forward to seeing the results!! Good luck!