Vaporization of wood, because it is important
When we talk about woodworking, one of the terms we often hear is "vaporization". But why is it so important? In this article we will see why it is important to do it and what are the processes for the vaporization of wood.
Effects of wood vaporization
The wood, fresh from the cut, is presented in non-homogeneous humidity conditions, because the quantity of water is not present along the entire trunk in equal parts. To promote better drying (and prevent the risk of damaging tensions) it is therefore necessary to standardize it. As we will see later this is possible thanks to the vaporization of the wood, which also allows to give the trunk a uniform natural color.
But the advantages of a perfectly performed vaporization are not limited to giving uniformity to the color and to the water vapor present on the trunk. Thanks to this process, in fact, it is possible to soften the woody fabrics, thus allowing an easier processing of the sheeter or the shear to obtain thin sheets from decorative veneers or plywood.
It should also be considered that with vaporization it is possible to remove those soluble substances contained within (such as starch, sugars and tannins) which could lead over time to the formation of fungi or the invasion of insects that would end up attacking and irreparably damaging the artifacts. Wood.
The vaporization treatment is normally applied to some essences such as Beech, Cherry, Walnut and some tropical species.
In summary, we can therefore summarize the advantages of wood vaporization in:
• ability to plasticise wood even in depth
• neutralize the action of fungi and bacteria
• obtain uniformity in color
• allow excellent results in bending
How wood vaporization is done
To be subjected to a perfectly professional vaporization, the wood must be freshly cut, in logs (for slicing or peeling) or in the form of sawn timber. Immediately after debarking, the trunk is hit by a jet of steam at 100 °C. The vaporization processes are carried out inside special chambers and can include:
- direct vaporization
- indirect vaporization
With direct vaporization, the vapor is introduced into the vaporization chamber through a series of perforated tubes placed under the stack of timber. The vapor must be saturated or nearly saturated and expand in the cell until it reaches atmospheric pressure. If saturated steam is not available, it is essential to act by moistening it. In this case the steam is blown towards the water present in a channel located under the steam pipe, positioned so that the holes are facing the floor.
Indirect vaporization can, in turn, provide for two different systems: the traditional one or with a direct burner. In the first case, the production of steam inside the cell takes place thanks to the boiling of the water contained in special stainless steel tanks, which are arranged below the floor level. The basins are located on three sides (excluding the one that sees the door) and under the stack. Inside there is a traditional heating coil, with superheated water or steam acting as a thermal agent. In the case of indirect vaporization with a direct burner, on the other hand, the inside of the tanks contains a heating coil activated by the flame of a gas burner. In both cases it is necessary to maintain a constant level of water in the tanks.
Direct Vaporization System vs Indirect Vaporization System
In direct vaporization the realization of the tube system is simpler, even if it is necessary to have saturated steam at low pressure.
Among the advantages of indirect vaporization we find a mild treatment of the wood, which prevents and reduces the risk of any damage. In addition to this, there is also the possibility of condensation recovery, with an obvious advantage linked to energy savings.
In both cases the whole system is controlled by a microprocessor, developed directly by WDE Maspell. This allows constant control of each step of the vaporization process, with the possibility of providing customized programs for each cycle according to the type of wood. Each program can be coded and recalled subsequently, possibly modified, to be used also in subsequent cycles. To ensure optimal vaporization cycles, specific sensors are then used to detect the temperature in the cell and in the core of the wood. In this way it is possible to have precise control of each process and a wood that is ready and perfect for any future processing.