The technology behind Accoya® Wood is based on wood acetylation, a process that has been studied by scientists for more than 75 years and proven to be an outstanding method of improving the technical properties of wood.

The process essentially alters the actual cell structure of wood by transforming free hydroxyl groups into acetyl groups. Acetyl groups simply consist of hydrogen, oxygen and carbon and are already present in all wood species (ranging from 1% to 8% by weight) and can be derived independently from acetic acid, i.e. vinegar. Thus, the process does not introduce anything to the wood that does not naturally occur in it.

The process can be summarised as follows:

 Acetic acid is ‘cracked’ by heating it to very high temperatures. Cracking breaks off a water molecule from the acetic acid leaving ketene which is used to create acetic anhydride.

 Water, acetic anhydride and un-cracked acetic acid must be separated and the water/acetic acid recycled, with the acetic acid sent back for re-cracking.

Acetic anhydride is reacted with wood at high pressure. This produces acetylated wood. The by-products are un-reacted anhydride mixed with acetic acid formed in the reaction.

 After the reaction, the mix of acetic anhydride and acetic acid by-product must be recycled.

The acetylated wood is washed (typically with steam) to remove residual acetic acid or anhydride and then dried.