I understand that heat treatment of wood if done properly increases the stability and durability of wood. I’m not very technically inclined but through some research I discovered some basic expletives for why wood becomes more durable, stable and changes to its beautiful color when thermally modified correctly.
Wood is composed of 50% cellulose, 23% hemicellulose, 20% lignin, and 7% other organic compounds, called extractives. Heat treatment removes resin, other extractives and their attached OH (Hydroxil) groups from the wood.
This process reduces water absorption of wood, consequently increasing decay resistance while decreasing swelling and shrinking. Another factor that contributes to the high durability of wood is the crystallization of cellulose. The change in hemicellulose increases the durability. Hemicellulose is separated into furfural and carboxylic acid. Caramelization of lignin, caused by heat, which results in the wood becoming darker in color.
I found that not all thermally modified wood should be treated equally. Many producers have come and gone within the industry over the years while many that remain struggle with the increasing demands surrounding the technology and the associated costs. The suppliers that remain relative to the demand of the marketplace, which seems to be increasing exponential around the world, will have to continue to invest millions of dollars to keep their technology up to date. The natural beauty, stability and durability of the wood can be lost if the thermal modification process is not done correctly.
When searching for reputable companies that manufacture thermally modified wood look for the “Thermowood” brand and logo which can only by the used by members of the International Thermowood Association. There is a company selling in North America called Novawood which is a member of this organization.