Green stuff on my fence - is it glue?
June 17, 2011 7:58 AM   Subscribe

There's some green, glue-like substance on several spots of my brand new fence (put up by a contractor along with a whole big reno). What is it? Is it easy to get off?
posted by evadery to Home & Garden (13 answers total)
Have you tried to wipe it off?

If that fails, why not talk to the contractor about it.
posted by TheBones at 8:08 AM on June 17, 2011

Can't wipe it off - am planning on talking to the contractor about it, but would like to have a better idea of what it is before I do.
posted by evadery at 8:17 AM on June 17, 2011

Looks to me like a splash of the stuff they use to treat the lumber. I'd take a hose to it and see if it goes away, with a sponge if necessary. Otherwise, yeah, call the contractor.
posted by valkyryn at 8:17 AM on June 17, 2011

I see something quite similar to this on the knots of the pressure treated lumber on my deck. I figured it is just sap discolored from the treatment. Alcohol will help dissolve sap, but I've never tried to remove sap from wood, just my own hands.
posted by wg at 8:33 AM on June 17, 2011

Looks like copper, which is what your pressure-treated lumber is treated with, among other things. Wash your hands after you trifle with it and don't put your fingers in your mouth.
posted by toodleydoodley at 9:12 AM on June 17, 2011

It's definitely sap + the pressure treatment stuff. It's glue-like because of the sap.

We put up a fence ourselves last summer and many of the fence pailings had these on them. I haven't worried about it myself and it doesn't bother me.

Not sure how to get it off, but I'm posting to suggest the possibility of not worrying... Good luck!
posted by cmetom at 9:18 AM on June 17, 2011

Could you scrape it off with a razor? Wear disposable gloves, and don't breathe in the dust- whatever they use to treat lumber is probably not great for humans.
posted by pseudostrabismus at 9:21 AM on June 17, 2011

The "not great for humans" component is arsenic, because it's also not great for termites nor carpenter ants. I would question building a fence out of the stuff. It's normally used for studs and other inside-the-wall construction.
posted by Citrus at 9:41 AM on June 17, 2011

Inside-the-wall wood is actually not pressure treated. P.T. wood is only supposed to be used if it's going to be in direct contact with the ground (which is damp, and provides access for insects). The fence is in contact with the ground, so pressure treated lumber is appropriate. It does leak through some types of paint, though. A stain-blocking primer might be in order, followed by another coat of regular paint, if you want to prevent the green sap from discoloring it further.
posted by Scientist at 9:49 AM on June 17, 2011

The "not great for humans" component is arsenic, because it's also not great for termites nor carpenter ants.

Arsenic is no longer allowed in treated lumber for the great majority of applications (dating back to 2004). This stuff is likely either alkaline copper quaternary or copper azole. I still wouldn't recommend eating it, though.
posted by jedicus at 9:51 AM on June 17, 2011

sap and pressure treatment stuff - the pattern and texture look just like sap, but the colour is the same as the treatment. if it really bugs you, try scraping it off with a drywall spatula - this will get off the crusty gooey bit, but you are unlikely to get the stain off completely, because the sap is coming from inside the wood.
posted by 5_13_23_42_69_666 at 9:59 AM on June 17, 2011

Assuming it's chmicals mixed with sap, washing it off might not work, even with a solvent (GooGone? GoofOff?) but scraping or sanding is probably a good bet. Not regular sandpaper (it would gum up quickly) but a mesh-type would probably work.
posted by aimedwander at 10:20 AM on June 17, 2011

Why is some treated wood green?
The green color you see on treated wood is caused by chemical reactions that take place between the preservative components and the wood. Copper is still the most widely used element in wood preservatives, and creates a green color on the wood. As wood dries and reacts to sun's ultraviolet rays, the green color will fade.

In other words, relax -- completely normal.

I don't think you can scrape or sand it off. The pressure treatment forces the chemical into the wood. It's not on, it's in.

Staining the wood, however, will pretty much obliterate the color, unless you use a very transparent stain. You should stain it anyway unless you look forward to it turning gray from the ultraviolet in sunlight. By then there shouldn't be any green showing, either.
posted by dhartung at 10:46 AM on June 17, 2011

« Older Could my protein powder be poisoning me?   |   Need help patching a Korg MS-2000 Newer »
This thread is closed to new comments.