What is wood heat treatment and what benefits can it bring to your wood?

Heat-treated wood, also known as carbonized wood or physically modified wood, is a type of modified material that undergoes a prolonged pyrolysis treatment at temperatures between 160°C and 230°C in an oxygen-free or low-oxygen environment to improve its physical, mechanical, and durability properties. This process, which does not rely on chemical additives, is an environmentally friendly wood modification technology widely used in construction, decoration, and outdoor projects.

The core mechanism is that high temperatures cause changes in the wood's internal chemical composition: hemicellulose degrades, reducing the number of hydroxyl groups, significantly reducing hygroscopicity and expansion and contraction rates, improving dimensional stability; lignin undergoes cross-linking, enhancing structural stability; and nutrients are destroyed, effectively inhibiting fungal and insect attack, achieving natural anti-corrosion properties. After treatment, the wood's equilibrium moisture content is controlled at 4% to 7%, its density is reduced by approximately 10% to 15%, and its thermal conductivity is lowered, resulting in excellent thermal insulation properties. The process consists of three stages: first, drying at 100°C to 130°C to reduce the moisture content to below 3%; then, maintaining the wood at a high temperature of 180°C to 210°C for 2 to 6 hours to achieve pyrolysis; and finally, humidity control to restore the moisture content of the wood. This equipment typically uses a closed reactor, with a PLC system precisely controlling temperature, pressure, and oxygen content.

Depending on the treatment conditions and intended use, heat-treated wood can be categorized as surface carbonized wood or deep carbonized wood. The former, which is only carbonized on the surface, is often used in handicrafts; the latter, which is uniformly carbonized throughout its structure and is also known as homogeneous carbonized wood, is suitable for indoor and outdoor decoration, flooring, furniture, and landscaping. However, this material is not recommended for direct contact with soil or prolonged submersion in water.