Biological alternatives to oil-based varnish are turning wood into one of the most sustainable building materials available.
Unlike PVC or aluminium, its feedstock is renewable, its production is carbon neutral and its waste is biodegradable, yet wood has one major drawback – it starts to degrade when exposed to moisture, harsh temperatures and bright lights.
Usually, the solution is to coat it in oil-based paints and varnishes – that’s good for the finish, but not so great for the environment.
One solution fresh out of the lab is a formula containing vegetable oil, a water-based solvent, and a pinch of inorganic nanoparticles.
‘The nanoparticles help reinforce the structural integrity of the coating and catalyse molecular bonds within it,’ said Carlos del Castillo, from Inspiralia in Madrid, Spain, who coordinated the EU-funded project ECOVARN that developed the mixture.
‘The result is a natural coating that is both reliable and looks good. That was not around before.’
Because coating formulations are extremely complex, swapping ingredients in them is tricky. Successful recipes owe at least as much to experimentation as they do to well-planned chemistry.
The efforts of the research teams at ECOVARN have been pushed further in the NEXT1KOAT project, which was coordinated by Francisco Melero from the Technical Research Centre of Furniture and Wood (CETEM) in Murcia, Spain.
‘We extract the raw materials from seaweed grown off the coast of Ireland and Scotland,’ he said. ‘A series of chemical steps then transforms the biomass into natural alcohols that we can process into sustainable paints and varnishes.’
In addition to benefits for the climate, these coatings present fewer health hazards to woodworkers and consumers. Furniture-makers using conventional wood coatings are obliged to work in well-ventilated areas and wear protective masks because the products are dissolved in toxic toluene. By contrast, many of the bio-based alternatives are water-borne.
As well as being safer, some of these new coatings and treatments can enhance the properties of wood, such as its ability to insulate.
M SORA, a window frame manufacturer in Žiri, Slovenia, has been working over the past years with the University of Ljubljana to develop better insulating window frames made of thermally modified wood.
Their product traps as much as twice the heat that earlier window frames can contain and even outperforms many plastic and aluminium frames sold today.
With support from the EU-funded WINTHERWAX project, M SORA and its partners are now attempting to coat this thermally treated timber in a naturally derived wax to increase its lifespan.
According to Dr Aleš Ugovšek, the project manager at M SORA who coordinated WINTHERWAX, dip-coating the timber and heating it helps cram the wax inside its cellular structure. The resulting surface is highly hydrophobic and unappetising to insects and fungi.
‘We are testing how well the wax extends the lifespan of our thermally treated wood in five test sites across Europe,’ said Dr Ugovšek. ‘So far, extreme cold in Sweden has damaged some of our testing equipment, but the window frames are all fine.’