Acetylation. What is it and what is acetylated wood?

An explanation of the mysterious wood technology behind Accoya® wood

If you search online there are academic journals and infamous online encyclopaedic entries that can answer the question ‘what is acetylation’ in a very scientific way. But rather than spin tales of hydroxyls, hydrogen atoms and other chemistry jargon, in the simplest terms we can muster (in the context of our wood technology) acetylation for us is:

Subjecting a softwood to a vinegar, which turns it into a hardwood by preventing the cells in the wood from being able to absorb water.

So acetylated wood is… Pickled wood?

More or less. Yes.

Ok the chemistry behind ‘turns it into’ is a little complex, and the vinegar is acetic anhydride. Not quite the malt vinegar for your fish and chips. But the principle is there. If you do want to know the chemistry behind acetylation, feel free to get in touch.

Acetic anhydride? Is that some toxic chemical?

Not at all. Don’t let the chemical name scare you. As sodium chloride is actually salt or dihydrogen monoxide is water. Nobody has come up with a sexy name for this vinegar yet. But importantly the reactive organic components are carbon, oxygen and hydrogen. So it’s not toxic at all.

Ok great so acetylation is non-toxic.

Why go to the effort of pickling, acetylating your wood?

To understand the benefits of using acetylated timber, we should point out the importance of acetylated wood not absorbing water.

When making anything out of wood, its water that’s one of the main trouble makers.

Keep wood dry and well maintained and it’s one of the greatest materials of all time. But introduce water? Problems begin to seep in. With untreated, badly treated or unmodified wood, water can bring a whole host of problems including rotting, warping, splintering, swelling, shrinking and being food for hungry insects.

So acetylation wood technology removes the issue at source. Rather than treating wood with a toxic chemical trying to keep the moisture out. The result is real wood that doesn’t rot. It doesn’t warp, swell or shrink. It doesn’t splinter and it isn’t termite chow. In fact removing all these traditional issues means that acetylated wood presents even more benefits than just ‘not failing’. It is so dimensionally stable (maintains its original shape and dimensions) that it’s perfect for coating and has outstanding durability. This wood, our wood, is branded Accoya®. Accoya® is acetylated wood. In fact Accoya® is the only acetylated wood, and in our opinion the only wood worth considering.

No longer at risk of traditional wood failure gives you confidence of longevity. Meaning any deck, cladding, windows or doors, boat, desk, fence, shed, giant wooden octopus, or whatever else you want to make, it’s going to last so much longer than any traditional alternative. So Accoya® is an investment in the future.

No water. No movement. No problem!

Sounds great, what’s the catch with this new-fangled technology?

Actually the technology isn’t new at all. Acetylation has been around for at least most of the 20th century. The problem is that it’s relatively easy to do it on a small scale, but very difficult to do large scale. It’s only recently that we’ve been able to acetylate larger volumes of wood consistently. So it has only been commercially viable and available since around 2007.

And there’s absolutely no catch. It’s a wonder material. Reliable, eco-friendly and sustainable.

How is using wood sustainable? Aren’t we cutting down the rainforests to get this wood?

We source all our wood from sustainable wood farms. So all the wood used is purposefully grown. This means we increase biomass; our acetylated wood is a carbon sink, good for the environment.

Cutting down rainforests is an issue with unsustainably sourced wood, and a problem with some traditional hardwoods.

An exotic hardwood tree may take hundreds of years to grow. Vast swathes of rainforest are cut down to find these old trees, to be turned into someone’s deck. Resulting in a huge carbon footprint and the destruction of natural resources.

What we want to do is provide even higher quality wood, but without any of the negative impact. Plus hardwoods aren’t all they’re cracked up to be. Oak, Teak, etc will still warp, rot, splinter, etc. Acetylated wood won’t.

Plus regardless of responsibly, sustainably sourced or not, most wood carries a carbon footprint higher than Accoya®. Our acetylated wood has an exceptionally low carbon footprint compared with alternatives.

So rounding back to the original question of what is acetylation? Technically it’s a chemical process. But we could say that acetylation is an opportunity for peace of mind, to invest in our homes and protect our planet.

Purpose grown Radiata Pine forest – New Zealand

9 Replies to “Acetylation. What is it and what is acetylated wood?”

  1. Riles says:

    How long would this timber last if say it was used to border a vegetable garden where the timber was in contact with soil at the bottom and one side. Would it never be subject to termite attack? Would it also be safe to use where it could be in contact with drinking water.

    1. accoya says:

      Thanks for the comment. Accoya is guaranteed 50 years above ground, 25 years below ground (in contact with), so would be great to border a vegetable garden. Accoya wood is also an effective barrier to termite attack, please find information here regarding Accoya and termites And lastly in regards to drinking water, if you email with your details, we can get in touch directly to discuss the exact needs. Thanks!

  2. RozaExperia says:

    Great post!

  3. Jim Baker says:

    Can Accoya be stained or sealed? If so, what is the process and what are the materials that can be used?

    1. accoya says:

      Hi Jim, yes Accoya can be stained and sealed. You can find the relevant information in the Accoya Wood Information Guide in our downloads section, or following this link.

      If you have further questions or would like to discuss in more detail please get in touch with us at


  4. Rolandio says:

    For a circular economy, Accoya wood is an excellent choice I figure.

    Why is it better than most other FSC (tropical) hardwoods regarding circular aspects?


  5. Tim says:

    Would all types of wood currently be able to be subjected to the acetylation process? I’m thinking here of wood species with increased densities such as locust, hickory, walnut. But also of very soft wood species like pine, which has a very short life-span below or in contact with ground, especially given modern water-borne/copper based pressure treatments, which are far less effective than older (and very caustic) methods such as creosote and CCA. I just had a split rail fence installed and went with locust posts because it is one of the most naturally rot/pest resistant species, but would’ve loved to have Accoya-treated locust posts!

    1. accoya says:

      The answer to the question is that it depends to a large extent (though by no means entirely) on the size of the piece of wood that you want to acetylate. When acetylating planks of wood on a commercial scale to achieve consistently high standards of performance as we do at Arnhem, there are only a small number of species that we can work with. However, if you chip the wood before acetylating it the range of species options is increased greatly, which is one of the drivers behind the construction of our factory at Hull to produce acetylated wood chips (Tricoya).

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