How to tell treated vs. untreated wood?

unkyakuApril 4, 2009

Can anyone tell me if there's a way to distinguish between treated and untreated wood?

I have some wood pallets that I'd like to convert into planting boxes, but I need to avoid treated wood so that nothing bad leaches into the vegetables. Any suggestions?


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Pooh Bear

Pallets are generally made of the lowest grade wood available.
I don't think you have any worries there.
Still, in this day and age of recycling, I suppose it is possible
that treated wood mite find its way into pallet production.
The old CCA treated stuff had a slight green tint to it.
The new ACQ treated stuff has a green tint when new.
After it has weathered a bit it might be hard to see.

If you can test the wood chemically it will show copper content.
Also it will show as alkali on a litmus test.
ACQ = Alkaline Copper Quaternary

Pooh Bear

    Bookmark   April 5, 2009 at 2:09AM
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Thanks for the information. As far as testing the wood goes, is there something simple I can pick up from Home Depot or something?

    Bookmark   April 5, 2009 at 2:49AM
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Pooh Bear

I don't know of a way to test wood for these substances.
I would try searching thru science experiments online
that deal with litmus tests and testing for metal content.

I really doubt you have anything to worry about.
Lumber treated with CCA has been off the market for a while now.
Now ACQ is used in the treatment process, and is safe.
The wood has a pH above 7 making it alkaline so bugs won't bother it.
And the copper quantenary molecules protect it from rot.
There is also MCQ, which is the same as ACQ, except the CQ
molecules are much smaller so more of them can infiltrate
the wood fibers. MCQ = (alkaline) Micro Copper Quantenary.

I would be very supprised if you had a pallet made of treated wood.
Especially treated with CCA (copper chromate arsenic).
CCA was banned sometime around year 2000.

Found this with a Google search:
The other method.......was patented by the University of Miami. It is a orange-colored chemical that you can spray on the wood with a spray bottle that will turn bright red in the presence of chromium, which is always present in CCA wood. The product is called PAN Indicator Stain, and was developed in 2003.

Last time I checked it was available from SPECTRUM (800-772-8786). The part number is P-358 and used to cost $21.90 + shipping. Please be sure to read the MSDS on this chemical  as it has to be handled carefully, as I recall. But, it works well, and I have a small amount on hand and have used it myself to identify CCA wood on my property.

ItÂs easy to use, too. You find an unpainted portion of the wood and spray it on. (Painted wood can test positive, due to trace metals in some paints, so use it only on unpainted wood.) After spraying, wait 2-3 minutes. If the color changes from orange to red or a darker color  it contains chromium metal and should be disposed of properly (and never burned  which will release the arsenic in the CCA).
You may could test for copper content by testing electrical
resistance in a sample of wood with a known moisture content.
Electrolosis is used for other substances, mite work for wood.
Swimming pool test kit that tests for copper might could work.
Burning a sample of the wood in a neutral flame would work.
If the flame turns green then the wood contains copper.
These are just brainstormed ideas. No guarantees about any of them.

I'd be interested to know if you find out anything.
Myself, planters have been built for many years using treated
wood. Even with CCA treated wood. I wouldn't worry about it.
Or if I had to worry about it, I would line the planters with plastic.

Pooh Bear

    Bookmark   April 6, 2009 at 8:09AM
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Thanks for all that detail.

I noticed that the pallets I had were stamped with "HT" and some according to Wikipedia that means that they've been heat treated, which I assume is fine in that no chemicals were used.

    Bookmark   April 6, 2009 at 1:12PM
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Pooh Bear

Just a guess, but heating them would remove most of the moisture.
That would help keep the weight down, decreasing shipping cost.
I have noticed that new pallets are extremely dry.
I'd have to look into this more tho.

Pooh Bear

    Bookmark   April 6, 2009 at 6:32PM
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As a rule, treated wood commonly sold to the public is pine. The treatment recipe turns the wood a bit more green than normal(CCA) and a lot mopre green(ACQ) than normal. The other treatments actually look like the wood has been painted green.

If the wood has aged to a gray color on the exterior, making a fresh cut to expose the interior will show the color. Yellow/white means no treatment.

PT wood is treated so the effects of time/insects/water do not have as much effect---the wood lasts much longer than untreated wood.

There are two basic kinds of pallets---heavy duty and one use. One use pallets are often made of pine. They are used for shipping appliances and small machinery. The wood is thin and can be torn apart easily. Heavy duty pallets are built for repeated use and sometimes have to be cut apart, as the glue/fasteners make tearing them apart very difficult. These types are usually made of white oak. I have never seen white oak treated with the same stuff that is used for pine.

    Bookmark   April 6, 2009 at 7:24PM
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Why not just get some cedar or cypress and build you planters out of wood you KNOW hasn't been treated. Most pallets aren't built out of wood suitable for this kind of project anyway. Save the pallets for flower planters or some other project.

    Bookmark   April 7, 2009 at 9:55AM
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Hi I have the same question. I have a piece of found wood labeled:

PRP 133
MILL 164

Also it says GRAVEYARD on it.

The wood does not look green, and I cut a piece off to check, and it is not green on the cut either. But, since I plan to use this in my garden I want to know for sure if it is safe to use. Does anyone know what this label and numbers mean?


    Bookmark   May 7, 2012 at 12:44PM
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it's 5/8" sheathing and from that I would have no way to tell for certain but I doubt very much that it was pressure treated.

    Bookmark   May 8, 2012 at 8:43AM
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Your wood is not treated. According to Teco website your wood was designed for indoor construction.

Here is the link i found my information.

Here is a link that might be useful: Teco explaination of markings

    Bookmark   May 8, 2012 at 5:00PM
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I agree with Mike. Why not get the best wood for your food project. Then you will also know it's food safe.

    Bookmark   June 5, 2012 at 12:22AM
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I was also wondering about the safety of pallets. I know it a few years later but I found several sites and I will attach one.

    Bookmark   February 18, 2015 at 6:49PM
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