Int Class Ext Class

190°C++no change

+

212°C++++-++

KEY PROPERTY CHANGES: SOFTWOODS

Treatment temperature

Durability

Dimensional stability

Bending strength

Colour darkness

Int 1 Class

Treatment temperature

Durability

Dimensional stability

Bending strength

Colour darkness

Int 2 Class

180°Cno change

+no change

+

200°C++-++

KEY PROPERTY CHANGES: HARDWOODS

Int Class

Pine(Pinus Silvestris)

Spruce(Picea Abies)

MouldingsFloorsInterior liningsFurniture

Exterior claddingTerrace floorsGarden furnitureWindowsDoors

Interior liningsFurniture

Exterior claddingTerrace floors

Ext Class

USES FOR FINNFOREST THERMOWOOD: SOFTWOODS

Int 1 Class

Birch(Betula Pendula)

Aspen(Populus Tremula)

WorktopsFurnitureFloorsWoodworkingInterior linings

FloorsGarden furnitureInterior liningsWoodworking

Sauna benchesSauna panelsFurnitureWoodworking

Sauna benchesSauna panelsFurnitureWoodworking

Int 2 Class

USES FOR FINNFOREST THERMOWOOD: HARDWOODS

Equilibrium moisturefalls by up to 50%

Bending strengthreduces by 10 – 20%

Dimensional stabilityincreases up to 50%

Improved rotresistance

Wood stainedthroughout

Resin has beenremoved

Improvedweather

resistance

Splitting strengthreduced by

approx. 50%SOURCE: VTT

Water absorptionreduces 50%

PEFC/02-34-07Finnforest ThermoWood® is a product certifiedby the Technical Research Centre of Finland (VTT)

THERMOWOOD

A Beautiful,Durable and

Environment-FriendlyChoice

THERMOWOOD IN BRIEF

Finnforest ThermoWood is produced by passing timber through

a cycle of heat and moisture changes involving exceptionally high

temperatures. The intensive heat treatment transforms the structure

and properties of the wood itself. The wood’s original natural

susceptibility to warping, swelling or shrinking in different

conditions of humidity is reduced by as much as 50 %. The resulting

ThermoWood is thus much more stable than normal wood in

changeable climatic and environmental conditions.

The equilibrium moisture content of ThermoWood is consid-

erably lower than that of ordinary wood and its resistance to rot-

producing fungi is equal to that of larch, oak or even teak, depending

on the degree of heat treatment. The ThermoWood production

process also improves the wood’s insulating properties and removes

resin from coniferous softwoods.

RANGE OF HEAT-TREATMENT

FEATURES AND APPLICATIONS

ThermoWood’s high resistance to moisture and rot makes it an

excellent material for outdoor furniture and wooden constructions

in gardens and terraces. It is not, however, suitable for conditions

where it would be saturated with water or in prolonged contact

with damp ground.

Excellent heat insulation and the absence of resin also make

ThermoWood’s properties ideal for warm and damp interiors such

as saunas or washrooms. Its low moisture content, too, means that

sauna benches made from ThermoWood are hygienic and less

burning to the skin than those made from ordinary wood. In

flooring applications, ThermoWood’s advantages include its

outstanding dimensional stability as well as its beautiful colour.

Intensive heat treatment imparts a whole range of attractive

brown shades and tones to ThermoWood. In general, the higher

the temperature of the treatment, the darker and richer the colour.

More information about different heat-treatment categories and

applications of ThermoWood can be found on the back page of

this brochure.

ENVIRONMENT-FRIENDLY

Finnforest’s ThermoWood production process is based on the

carefully controlled use of heat and steam. ThermoWood production

does not involve chemicals that pollute the environment, and no

other substances are added or applied to the wood during the

treatment process. ThermoWood thus has no adverse effects at all

on the environment. The total energy consumption of the

ThermoWood production process only slightly exceeds that of

normal timber drying.

Any waste resulting from ThermoWood can be harmlessly

burnt or otherwise destroyed without risk to the environment.

Another important benefit from the environmental point of

view is that timber from almost any tree species can be used as

raw material for ThermoWood. Sustainably managed softwood

from Finland that has been processed to ThermoWood displays

properties that are remarkably similar to those of many tropical

hardwoods.

WORKING WITH THERMOWOOD

ThermoWood can be sawn and worked in the same way as ordinary

untreated timber. It is easy to use all sorts of hand tools for cutting,

drilling and planing. An excellent surface can be created without

any difficulty, and drilling through knots is also easy.

ThermoWood is somewhat more likely to split than untreated

wood and this should be taken into account when working with it:

dropping a piece might damage the edge and long planks should

be lifted from both ends.

When using hand tools, care must also be taken with regard

to the sawdust that is produced. As ThermoWood is so dry, it

creates a fine dust that easily spreads in the air. If there is no dust

removal system in the workshop, a dust mask should be used.

www.finnforest.fi

USING NAILS WITH THERMOWOOD

A pneumatic nail gun is a good tool for fixing and securing

ThermoWood. The best results can be achieved with a small

compressed air gun that has an adjustable nailing depth. Nails

should be sunk to a depth of about 1mm.

Care must be taken when using a normal hammer because the

wood may split if it suffers a direct blow. It is advisable to make

sharp nails slightly blunt before use and also to use a nail punch

for the last 2–3 mm when hammering them home.

Stainless steel nails are good to use to avoid rusting dis-

colouration. Galvanised nails can be used with a pneumatic nail

gun since there is no metal-to-metal contact that can damage their

protective surfaces. Galvanised nails are also very suitable for use

with outside cladding boards that will be painted. Small oval-

headed nails reduce the risk of splitting.

USING SCREWS WITH THERMOWOOD

Careful drilling of holes and countersinking so the screw heads

are level with the wood surface are just as important when working

with ThermoWood as with hardwoods or brittle composite materials

such as MDF. Stainless steel screws with countersunk heads are

most suitable for use outdoors and in humid environments. Screws

with a limited number of threads provide the optimal strength.

Self-tapping screws can be used with ThermoWood without the

need to drill individual holes for them.

GLUING THERMOWOOD

Heat-treated wood is slow to absorb water and water-based

glues such as PVAc, the commonly used woodworking glue.

Longer compression and drying times than normal are thus

necessary when using water-soluble glues. The glue used should

also contain a high proportion of solid material.

Chemically hardening glues, such as polyurethane and resin

glues, can be used with ThermoWood in the same way as with

ordinary wood.

As in all types of wood gluing operation, the best results are

obtained with ThermoWood by making sure of optimal working

conditions, such as wood temperature and moisture content, surface

cleanliness, and so on. When gluing ThermoWood, too, the glue

manufacturer’s specific instructions must always be respected.

TREATING THE SURFACE OF THERMOWOOD

For exterior use it is best to apply a surface coating to ThermoWood

because prolonged exposure to the ultraviolet radiation in sunlight

causes greying in colour and possibly also slight cracking.

Colour changes can be prevented by protecting the wood with

a coating that contains some pigment. The most commonly used

material is a transparent base with some brown pigment added that

matches as closely as possible with the original ThermoWood

shade. In many cases, however, this results in a slightly darker

appearance. Different types of coating also need renewing at

different intervals. In general, the coating lasts longer as the amount

of pigment increases, but increasing pigment content further

conceals the ThermoWood’s original colour and texture.

Whatever the coating used, its manufacturer’s specific

instructions must always be respected.

THERMOWOOD IN SAUNA BENCHES

Sauna benches made from ThermoWood boards can easily absorb

water through the ends of the boards. Fast cycles of wetting and

drying in the hot sauna surroundings can also cause the boards to

crack at the ends. The ends of sauna benches should therefore be

sealed with oil, wax or varnish.

Strong alkaline detergents and hard scrubbing should be avoided

when cleaning ThermoWood benches so that the surfaces maintain

their natural good looks and condition.

KEEPING SURFACES IN GOOD CONDITION

Climate and environmental factors directly effect the performance

and useful life of surfaces and coatings. Ultraviolet rays from

sunlight and moisture in the air are major factors causing surface

deterioration. That is why, for example, the south side of a building

often needs painting more often than the north side. And the surface

coatings of buildings in dry continental climates often last longer

than those of buildings by the sea.

To ensure the optimal performance of protective coatings and

avoid damage and deterioration, all surfaces should be cleaned

and checked annually. If defects are found they should be repaired

immediately.

Always refer to the paint manufacturer’s specific instructions

about renewing coatings.