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When quality counts

More and more quality-conscious companies are turning to Stellac as their supplier when they want to build plants for producing Thermally Modified Timber (TMT). As a result, growing quantities of high-quality flooring, decking, siding, and other TMT products are now being produced worldwide using the Stellac® Process.

People have known that heat can improve wood’s ability to resist decay for thousands of years, and the phenomenon has been scientifically investigated since the 1920s. It was not until quite recently, however – around 10 years ago in fact – that a way was found to manage the process. Drawing on this work, Stellac has developed the Stellac® Process for thermally modifying wood on an industrial scale.

The reliability of the system’s equipment and the process itself ensures that every batch of Stellac® Wood meets high quality specifications with the best possible yield. By managing the start-up of new plants using the technology, carefully monitoring quality, and training operators, Stellac is able to ensure that the product always meets customers’ expectations.

Durability without the need for impregnation

Stellac® Wood’s excellent resistance to decay makes it an ideal, environmentally compatible alternative to chemically treated timber in applications where wood is exposed to high levels of moisture or comes into contact with the ground or water. The darker colour of Stellac® Wood compared to conventional timber, resulting from the chemical changes triggered by the process, also make it a visually attractive alternative.

Although spruce, pine, beech, ash, and aspen have been most widely used in the Stellac® Process so far, it is suitable for all types of timber.

The process takes between 20 and more than 75 hours, depending on the thickness and moisture content of the material and the type of wood used, and exposes the timber to temperatures of between 200 and 250 °C. During this time, the sugars in the wood are decomposed into compounds that cannot be utilised by fungi, and natural protective agents in the wood are released.

These changes are permanent and improve wood’s resistance to rot and mould dramatically, making it easy to achieve the highest Class 1 and 2 standards of resistance to fungal attack. Studies have shown that many years of direct contact with the ground have no effect on Stellac® wood at all.

The process also changes timber’s physical properties, reducing moisture deformation, shrinkage, swelling, and water absorption.

Thanks to this range of sought-after properties, the endproduct represents both a highly sustainable alternative to tropical hardwoods and an ecologically friendly alternative to chemically impregnated timber.

Stellac® Wood produced by KosHii & Co, Ltd. in Osaka has been used to provide exterior cladding for these buildings at the University of Tokyo, highlighting how well its aesthetic and technical qualities live up to the highest standards.

Guaranteed environmentally friendly

No toxic substances are used in the Stellac® Process, making the production, use, and disposal of Stellac® Wood environmentally benign and keeping the exposure levels of people working with the process to a minimum. Thermally modified wood can be disposed of in exactly the same way as untreated timber, unlike impregnated timber.

Stellac® Wood is manufactured using only timber certified under the Pan European Forest Certification Scheme (PEFC) from stands that are managed according to ecologically, economically, and socially sustainable principles. In addition to using only PEFC-certified timber, the Stellac® Process also only uses energy generated according to agreed green principles. The Stellac® Process has been recognised for the quality of its output, and the Finnish authorities have granted a best practises declaration covering both the process and Stellac® Wood.

A grade for most needs

Five grades of Stellac® Wood are available. The premium grades, covering timber that has been processed the longest, are designed for applications where the highest levels of decay and weather resistance are a priority, typically outdoors. The other grades are suitable for applications that call for medium resistance to moisture-related deformation and particular colours. Whatever the grade, Stellac® Wood can be worked and finished just like untreated wood.

The most common applications for Stellac® Wood are cladding, siding, decking, playground and garden furniture, window frames, doors, noise barriers, and jetties and pontoons.

Thermally modified wood can also be used inside – in parquet, wall panels, kitchen units, and sauna interiors. Stellac® Wood makes an excellent material for everyday furniture, accessories, and decorative goods, and has even found application in musical instruments and boats.

The right process

Stellac supplies thermal modification units tailored to customers’ specific needs. Units or combinations of units are available with an annual capacity ranging from 1,000 m3 to 50,000 m3 or more.

Stellac® systems are available for processing both fresh sawn goods and naturally dried or kiln-dried timber. PC-based software monitors and controls the various stages of the process to ensure that timber has precisely the required final moisture content.

Firstwood, based in Premnitz in Germany, is one of a growing number of timber suppliers to have selected the Stellac® Process. The first phase of the company’s Stellac-supplied facility, which was commissioned in autumn 2009, is capable of processing 8,500 m3 of timber annually in its twin kilns. Output – which will focus on pine, beech, ash, and birch – will be marketed under the Firstwood® brand.

> Seppo Paavilainen
(Published in HighTech Finland 2010)