This method of improving wood has been proven to deliver such superior performance that it has long been used as the "gold standard" against which other methods are measured. Medite Tricoya combines this science with years of proprietary research and investment by Accsys Technologies.

The physical properties of any material are determined by its chemical structure. Wood contains an abundance of chemical groups called "free hydroxyls" (represented as OH in the chemical formula opposite). Free hydroxyl groups absorb and release water according to changes in the climatic conditions (moisture content) to which the wood is exposed. This is the main reason why wood swells and shrinks. It is also believed that the digestion of wood by enzymes initiates at the free hydroxyl sites - which is one of the principal reasons that wood is prone to decay.

Acetylation effectively changes the free hydroxyls within the wood into acetyl groups. This is done by reacting the wood with acetic anhydride, which comes from acetic acid (known as vinegar when in its dilute form).

When the free hydroxyl group is transformed to an acetyl group, the ability of the wood to absorb water is greatly reduced, rendering the wood more dimensionally stable and, because it is no longer digestible, extremely durable.

Acetyl groups are already naturally present in all wood species as well as in humans and other mammals. This means that the manufacturing process adds nothing to the wood that does not already naturally occur within it, resulting in an end product that does not add toxins to the environment.

The effect of altering the wood's chemical structure, as opposed to merely altering its chemical content, is essentially to create a new product that is modified right through the cross section. By contrast, other comparable treatments merely insert chemicals (such as oils, ammonia or metal compounds) into the wood, improving durability but not dimensional stability.