How and why to dry wood
When a tree is cut down it contains a large amount of water. The percentage of liquid present in the trunk of the plant (cell lumens and cell walls) can vary according to the wood species and the growth environment, remaining however within a range between 50% and 300%.
After its abatement, the first to come out is the free water contained in the cellular lumens. This first process leads the wood to lose weight, without however affecting its volume. When the trunk reaches humidity values of around 30%, even the water up to that moment linked to the cell walls begins to escape. This threshold, also known as the saturation point of the cell walls, marks the point from which any further loss of liquid also leads to a decrease in volume (the so-called shrinkage of the wood). The shrinkage of the wood occurs in three different directions: longitudinal, radial and tangential. Obviously, the percentage of humidity that the dried wood must have must be chosen based on the use we are going to make of it and the environment in which it will be placed: the construction timber must have a higher percentage of humidity than that intended for the construction of furniture. for internal. In fact, let's not forget that wood is a hygroscopic material, that is, capable of adapting to the surrounding environment by giving it moisture until it reaches a point of equilibrium with it. Only when it reaches the desired level of humidity can the wood be processed safely, as it will no longer present any risk of cracking, alterations linked to fungal attacks and the presence of fungi and insects that may already be present. Only a perfectly dried wood can therefore guarantee optimal and long-lasting results.
Natural drying or wood dryers?
To intervene on the three factors that influence the drying process of wood (temperature, humidity and air circulation) there are two different curing processes. The first involves a natural process. The timber is stacked neatly in planks sheltered from rainwater and direct sunlight. Between one row and the next, spacer strips are inserted to allow greater air circulation. This drying method obviously requires very long times (we are talking about one year for every centimeter of thickness of the board). It will then be necessary to pay close attention to the removal of wood waste, which could be affected by fungi and represent a risk of contamination for good wood. These are not the only disadvantages of natural drying, because with this system it will be impossible to lower the percentage of humidity below 12%, thus making the boards suitable for some specific processes such as the construction of parquet. If we want to further reduce the amount of humidity present in the logs we should resort to drying wood indoors and not outdoors.
On the contrary, drying wood in special ovens allows you to speed up the process and regulate the temperature, in order to optimize the process and prevent the risk of splitting of the wood. Among the most popular artificial drying systems are those carried out under vacuum. The vacuum drying involves the insertion of the wooden stacks in special watertight stainless steel chambers and the subsequent reduction of the atmospheric pressure. Thanks to special heated panels, or through ventilation of the stack, the heat is then transmitted to the wood, thus leading to a process of water evaporation.
These are undoubtedly machines able to offer certain results with significantly shorter times, which allow companies in the sector to amortize purchase costs in a few years and obtain a truly surprising ROI (return on investment). The new National Transition Plan 4.0, one of the pillars of the Italian Recovery Plan, which includes important changes in the Budget Law, makes it easier for companies that are thinking of equipping themselves with high-efficiency machinery, or replacing outdated models. The tax credit provided for investments in material assets allows companies in the wood sector to invest in research, development and innovation, thus increasing their competitiveness
For more information on the most modern drying ovens and wood seasoning systems, do not hesitate to contact us.