Jul 11, 2019

What is wood drying ?

It is a set of operations that consist of reducing the humidity level of the wood by removing some of the water it contains. Wood drying is done by convection. This technique is based on two principles: energy input and humidity removal. The wide range of drying processes now makes it possible to dry according to its needs.

Why dry the wood?

These operations enable:

  • Use woods with moisture contents in hygroscopic equilibrium with the medium of their use.
  • To obtain relatively stable structures
  • To reduce the risk of alteration and disorders caused by attack of fungi and other parasites

What are the moisture contents to respect?

The moisture contents to respect depends on the wood and the type of manufacture (furniture, joineries, parquet floor, frame). It can go from 6 % to 30 %.

What phenomena are present?

Water migration occurs from the inside to the outside of the material. The characteristics of the wood material will play on this phenomenon in the following way:

Wood species Heavy wood The wood drying time is long
Light wood The wood drying time is short
Size of cut wood Thick wood Slow migration
Thin wood Quick migration
Direction of wood fibres Axial direction Quick migration
Radial direction Slow migration
Tangential direction Very slow migration

The characteristics of the ambient air will affect the evaporation on the surface of the material as follows:

Air speed High It activates the evaporation
Low It slows down the evaporation
Air temperature High The evaporation is substantial
Low The evaporation is slow or zero
Hygrometric state of the air High humidity The absorption is minimum
Low humidity The absorption is maximum