The process
We have been working on Retification since 1997, therefore opening the way to wood’s thermal treatment and preservation using an ecological and healthy process. The obvious interest in such a procedure has lead some to follow us, transforming the offer of thermally modified wood into a complex business ground where Retification has become a reference.
Retification is an exclusive and patented process, which exploits the discoveries of Saint Etienne’s Ecole des Mines in order to give wood optimal proprieties. The temperature, the amount of time the wood is treated are a few of the numerous parameters which allows our wood to keep its initial qualities and enables us to obtain the best compromise between mechanical resistance, dimensional stability and durability.
Temperature
Wood’s exposure to heat is the basic principle of Retification. Without adding any products, it leads to a definitive physical and chemical transformation of the wood’s components, which distinguishes our process from a simple drying. This thorough modification of the wood’s structure alters the nutriments in the wood, modifies its hydrophilic and its dimensional stability. It also affects its mechanical performances.
We only treat perfectly dried wood. In the first phase of treatment, the wood will go through an intense drying, reaching temperatures from 160°C to 180°C. At this stage the wood is not “modified” and its state remains reversible. Beyond this point, the modifications of the wood will be definite. The wood’s original shade, stability and durability parameters will progressively evolve. One of Retification’s specificity is working at a range of temperatures which corresponds to each species “glassy transition phase”. In order to reach this narrow bracket, which is specific to each species, we must expose the wood to temperatures reaching 240°C. This highest temperature, the length of time the wood has to be exposed and the total time lapse of a cycle are many of the factors which condition the quality of the treatment.
Once this maximum temperature is reached, the wood is cooled off by sprinkling. It progressively goes back to its normal temperature, temperature at which it will keep the stability and durability proprieties it acquired at high temperatures.
O²
Exposing wood to temperatures reaching 240°C without degrading it requires extreme accuracy and a thorough respect of curbs, patented, is Retification’s speciality. It also requires the perfect handling of an element which is essential in the wood’s reaction at high temperatures: oxygen.
It is oxygen which enables the wood’s combustion in the air. It also is thermal treatment’s worst enemy because this process’s objective is to preserve the wood’s qualities. Its presence in an oven not only leads to risks of combustion but also to a less evident degradation of the wood’s components: oxidation.
The presence of oxygen during the high temperature process considerably degrades the wood’s mechanical properties. Retification takes place in an inert atmosphere, without any oxygen. It is what makes our treatment unique, allowing us to propose wood which is durable and stable while conserving most of its mechanical properties.
Ovens
Retification® requires a tool which enables to unite the process’s own heat and atmosphere parameters: the Retification reactor.
The wood will reach its Retification temperature in an enclosure, under regulated atmosphere. It is then cooled off by water sprinkling.
Loads are made up of the same species, in the same section, in order to guarantee a homogeneous and equivalent treatment for each board. Each load will go through a specific heating, established by a special Retification graph.
Traceability
Because our desire is to fit in an environmentally friendly process, Retification is respectful of the environment, therefore we guarantee a very careful monitoring of the wood we treat.
Our supplying, results of business relations with saw mills which share our values, is mostly of French origin and try to emphasize the quality of local species. Chopped down in France, sawn and dried in France, carefully transported by us to our facilities, the wood is subject to a careful analysis which allows us to follow each batch right up to its sale. The small part of our wood which is imported is essentially Spruce tree, coming from Northern Europe, and is systematically labelled PEF
.
Energy costs
We are as careful with the proximity of our supplying as we are with our treatment’s energy costs.
The total lifespan of a product, and therefore the calculation of its production’s energy cost reflect on all the stages which follow the material. Our local supplying minimizes the transportation stage and its effects on the environment. What is left to quantify is the energy used to retify.
Species
| Sawing + Drying (MJ/kg)*
| Retification (MJ/kg)
| Specific energy
consumption (MJ/kg)
|
Pine tree
| 1,5
| 2,3
| 3,8
|
Poplar
| 1,9
| 1,8
| 3,7
|
| |
| *(Data from CBTA) |
à titre indicatif :
- Solid wood 2MJ/kg
- Particle Panel 4MJ/kg
- MDF 11MJ/kg
- Extruded PVC 41MJ/kg
- French Aluminium 74MJ/kg
Retified® wood is today the material with the lowest specific energy consumption. But that doesn’t stop us from continuing our efforts in order to reduce it even more, we try finding shorter circuits, handling the material better and optimizing our ovens.
Prescriptive readability
Because we desire to offer the best possible readability in the performances of our wood, we do everything in our power so that the performances and limits of each species are perfectly evaluated.
Although it has been used for nearly 10 years, Retification is still considered as a new process, without any specific prescriptive background.
The durability of the wood is evaluated by the European norms EN 350 and EN 113. This durability ranking is the opposite of another, better known, European norm which establishes risk groups: EN 335
As we await the arrival of a norm specialised in the modification of wood due to heat, we chose to position ourselves thanks to those norms, based on the work of the CSTB and the CTBA.
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