Coated panels at Asa

How to choose wood material for coated products to last longer

The choice of wood material plays a major part in the durability of a painted wood panel. That there is less mould growth on the heartwood, that the growth is also affected by the colour of the panel and that broad annual rings in the wood gives fewer cracks are some of the results of new research at Linnaeus University.

Spruce is one of Sweden's most common species of wood and is often used for house façades. But different parts of the log have different characteristics and the choice of wood is therefore important if you want a panel that lasts longer. However, no account is taken of this today for wood used for house façades, for instance.

At the department of forestry and wood technology at Linnaeus University, research into the durability of coated wood has been done for a long time. During the last five years, an experiment has been carried out where painted panels of wood from spruce were exposed to wind and weather.

The panels were coated with commercial paint systems, i.e. alkyd paint, acrylate paint or linseed oil. The wood material was heartwood (from the middle part of the tree) or sap (from the outer part of the tree), with two different widths of annual rings.

"We found that panels with wide annual rings had fewer cracks than those with narrow ones. This was especially true of panels painted with diffuse-open coatings. Fewest cracks had panels of fast-grown heartwood", says Tinh Sjökvist, doctoral student in forestry and wood technology.

Regarding the microbial discoloration on the surface, it was found that panels of heartwood were least affected. The researchers also found a clear effect of the coloration. After five years the panels coated with red paint were completely free from growth, while all white panels had a varied degree of contamination and growth.

"We can expressly see that the choice of wood material has a clear effect on the durability of a painted panel, in a number of ways. This is an important support for our further research with the aim of developing coated wood products with higher durability and longer maintenance intervals", says Åsa Blom, associate professor and head of the department of forestry and wood technology.

The study is part of the Bridge, a collaboration between Linnaeus University and IKEA, with the goal of creating a better everyday life in our homes. In the study, the trade organization SVEFF has contributed.

More information

  • Tinh Sjökvist, doctoral student in forestry and wood technology, +46 (0)70 379 42 10,
  • Åsa Blom, associate professor and head of the department of forestry and wood technology, +46 (0)70-687 05 15,
  • Anders Runesson, research communications officer, +46 (0)70-70 81 70,

Read Tinh's and Åsa's popular scientific summary (pdf file, 660 Kb, in Swedish).