Thermally Modified Wood Started with the Vikings!
Thermally modified wood products have been used widely for more than 20 years in Germany, Austria, Norway, Switzerland, Japan and Italy for both interior and exterior applications. Centuries ago, the Vikings learned to overcome the shortcomings of natural wood by treating it with fire. They discovered that burning the surface of cut wood made it more resistant to the effects of outdoor exposure. It was only within the last century that Europeans perfected the thermal modification process. And by adding steam, found that the structure of wood was further modified, making it more impervious to rot, mildew, and decay.
What Does Thermal Modification Do to Wood?
Thermal modification is now a highly technical computer-controlled process carried out in specially designed high-temperature kilns. Only heat and steam—no chemicals—are used.
When hardwood is thermally modified at temperatures over 400˚F, the wood’s chemical and physical properties are permanently altered. Different from kiln drying, which only reduces the moisture content of timber to a range of 6 – 8%, the thermal modification process reduces the wood moisture content down to a very low range of 0 – 5%.
Two of the popular ways to thermally modify wood are in open systems (not under vacuum) and closed systems (under a vacuum). Open systems reduce the moisture content to zero, but cause more stress on the wood and its physical properties. Closed systems reduce moisture content to approximately 5%. This process changes the physical structure of the wood, resulting in changes that improve the performance of the wood, particularly in exterior applications.
What Physical Characteristics are Different with Thermally Modified Hardwood?
The thermal modification results in hardwoods with outstanding dimensional stability and rot-resistance. The ability of the cells in wood to transport water is reduced, resulting in water-resistant properties. The sugar content in the wood cells is also reduced, minimizing the food source for mold and fungus. These two physical changes in the wood result in a hardwood product stable and durable enough for exterior applications – much as the Vikings used it.
Natural Rich, Brown Color Created with Thermal Modification, No Stain Needed
The color of the wood is transformed throughout the thickness of each board. The color of “medium-treated” wood varies from light to golden brown, while the “intensely treated” wood is a chocolate brown. Because of the stability and color change, thermally modified products are considered an environmentally friendly alternative to engineered and exotic products.
Why is Thermally Modified Hardwood a Great Product?
Thermally modified hardwood is a natural, chemical-free material – a safe, green alternative to chemically preserved wood. It is excellent for exterior applications where weather-related decay and stability are essential. You can expect years of service with minimal maintenance from this sustainable alternative to tropical imports such as teak and ipe.