Timber iQ Dec 2017 - Jan 2018 // Issue:35 | Page 17

COVER STORY
an industrial scale. Decades later the Technical Research
Institute of Finland became interested in the idea and as a
result, the technique was developed, innovated and
enhanced into the 21st century. Thermory experts have
spent years perfecting the process to bring this unique
finishing into modern homes and public spaces.
The process is conducted in the industry’s top thermal
modification kilns using heat and steam. Lumber is slowly
heated to about 215°C, while controlling the moisture
content through means of steam. Under the influence of
high temperature, the chemical and physical properties of
wood undergo permanent change. The end phase of the
process is cooling down and re-moisturising to bring the
timber to the normal equilibrium moisture content of 5 to
7%, which is suitable for machining, installing and using.
PROPERTIES
The timber fades to grey if left unfinished but remains stable
and durable.
The stability of Thermoash put to the test in this Norwegian
bathroom.
developed an environmentally responsible solid product
that delivers unrivaled luxury and out-performs the finest
tropical woods. With stunning, exotic colour, Thermory is a
responsible, yet sophisticated green alternative to
mainstream tropical hardwoods which have no
long-term renewability.
THE PROCESS
The method of treating wood with fire to make it more
durable was known centuries ago. Ancient Vikings burnt the
bottom of their boats to make them resistant to corrosive
effect of salty waters.
Studies on the possible benefits of thermal modification
of wood began as early as the 1930s and 1940s in Europe
and the US, but the manufacturing process never reached
Durability and stability are the main advantages of
Thermory wood. Thermo-treatment changes wood’s
chemical composition and the depolymerisation of lignin
under influence of high temperatures reduce the length of
chains of cellulose. In other words, most of the wood sugars
are cooked out, eliminating the food source for mould,
fungus and biological decay. The side effect of this process
is change of the colour of the wood through the entire
thickness of each piece; the colour becomes more sated and
homogeneous on all sections.
However, the main effect is the increase of biological
durability. Thermo-treated wood does not require any
chemical protection. The high heat eliminates conditions
for occurrence and duplications of fungus or
microorganisms and bio-damaging agents are destroyed.
According to tests, Thermory Thermoash has durability class
1 (over 25 years of service life outdoors) and Thermory
Thermopine has durability class 2, which means 15 to 25
years of (a carefree) lifespan.
Thermory Thermoash and Thermory Thermopine are
superior in durability to tropical wood species and at the
same time have much better dimensional stability.
As the result of thermal modification, cellular structure of
the wood is altered to reduce movement related to
moisture. Equilibrium moisture content of Thermory wood
is reduced 50% compared to untreated wood, and this
difference remains after years of exposure. Swelling and
shrinkage of wood strongly depends on the absorptive
qualities of the wood, and in Thermory wood it is reduced
five to 10 times for hardwoods and two to three times for
softwoods. Thanks to its high resistance to heat and
moisture, Thermory is a perfect match for applications
where natural materials would normally fail such as around
pool areas, at waterfronts, in rooms with high humidity and
on top of heated floors.
Other important properties are decreased moisture
permeability (this concerns not only water, but also oils and
glues) and decreased thermal conductivity. Thermory
wooden deck will always be much cooler on hot summer
days than any other deck, thanks to lower water content
and structural changes.
// DECEMBER 2017 / JANUARY 2018 15