The beauty of timber is that it is a natural product. But, while knots, shakes, joints and grains might hold the upper hand in aesthetics, they give wood an unpredictability which presents certain challenges – particularly for anyone wanting to develop a powder coating for the exterior joinery market.

With a number of companies taking tentative steps to examine the possibilities of powder coatings on wood, there is certainly growing interest in a technology that already has proven credentials.

Powder coatings are already used extensively for external building products like metal window frames and cladding, and can offer a number of advantages over wet coatings, as Peter Rieck, managing director of Sonneborn & Rieck, explained: “There are no solvents involved, there is a high level of recyclability and you can apply much thicker and more durable films. Also, there is less likely to be colour degradation and staining.”

It was with this in mind, that a FIRA-led project kicked off in April 2003 to develop a factory-applied powder coating for use in the exterior joinery market. Completed last year, the project aimed to boost confidence in the performance of wooden joinery.

Although the project did not result in the commercial development of powder coatings for external timbers, it did show the potential.

Significant benefits

Sue Calver, from FIRA International Ltd, is convinced that powder coatings have significant benefits and could increase the competitiveness of timber over rival materials for exterior use. “The use of factory-applied powder coatings to protect exterior components within the construction industry would exploit the current trends towards greater use of factory pre-finished joinery,” she said.

“Factory pre-finishing of joinery is highly beneficial to the construction industry, allowing the use of more sophisticated, high performance coatings and greater control over their application than on-site procedures.

“The potential inclusion of powder coatings as protective coatings for joinery will significantly extend the specification options currently available for exterior coatings applied under controlled factory conditions.”

The project, which involved TRADA and a number of industry partners, aimed to show the benefits that powder coatings could bring, such as joinery finishes which offer quality and ‘controllability’ of factory application; economy, compared with on-site painting; low VOC finishes; and high performance expectations.

Its purpose was to demonstrate that powders were capable of at least matching the ‘mid-range’ performance of conventionally-applied coatings. Any that did so were earmarked as potentially suitable for market exploitation within the wood joinery sector.

Applications

Some companies are already exploring the potential. Howarth Windows and Doors, for example, is looking at how powder coatings could be used on its composite windows and MDF-panelled doors. Factory manager Michael Toner explained: “We have been looking at something that would provide a patination to make MDF look more ‘woodlike’, although we wouldn’t be using it on our solid timber windows.

“By using a composite window that can be made to look like wood, people can have a low maintenance product,” said Mr Toner.

Others believe there is still more work to be done. “Given the state of play at the moment, powder coatings [for external joinery] are still in danger of being blackballed because their performance is not yet at that level where they can compete against wet products,” said Peter Rieck. “Powder coating would be a viable option if we could take the technology a step further in terms of combining the properties we already know exist and applying them to a softwood or hardwood frame.”

Mr Rieck believes that with the right type of research into the flow of powder coatings and the chemistry involved – by all companies in the chain – the potential is there to be exploited. “But it will need a driver,” he said, “a combination of companies who are prepared to stick their necks out and push the development.

“As the challenge increases to find materials that are increasingly better for the environment, powder coating must be one of the technologies we take forward,” he concluded.

Whether it will find commercial viability in exterior joinery, only time – and more research – will tell.