Drying: the heart of the process
Drying the wood is one of the most delicate processes. This is where wood flooring production demonstrates major similarities with the cultivation of other natural materials, where the end result has a massive impact on quality and price, like with wine and coffee.
Drying is not something that can be forced. Different wood species require different drying times. The dimensions and moisture content of the wood before drying play important parts. Drying wood is a science in itself. Kährs uses two drying techniques, with experts in the R&D department working constantly to refine and improve the methods.
“Drying is the most critical of our processes. If we don’t do the job properly, it will have consequences further down the production chain. We have to maintain the right moisture balance between the core lamellae and the surface. If we fail to achieve that balance, the boards will end up concave or convex,” explains Torbjörn Lagesson, Production Manager at Kährs.
We’ve done a lot of air drying over the past few years, ensuring good quality. We can’t change the laws of nature!Torbjörn Lagesson, Production Manager at Kährs sawmill
Cannot change the laws of nature
After sawing, the moisture content can be as high as 90%.However the surface layer of each of the boards has to have a moisture content of 6% when they are fitted together.
“We measure the moisture content before, during and after drying so as to ensure the wood’s quality before sending it on,” says Torbjörn, explaining that air-drying is often preferable as it results in less cracking and discolouration.
“We’ve done a lot of air drying over the past few years. Air drying is essential for good quality. It’s hard to imitate air drying with fresh drying. We cannot change the laws of nature!”
In Sweden, air drying is only possible from late March until Midsummer. The climate during the rest of the year makes it impossible to air dry. “Air dry” means a moisture content of less than 20% in the wood.