Experimenting with different timbers in furniture making: Making with acetylated wood
We encourage our students to learn about and work with a range of sustainably sourced timbers. We’ve had students using more unusual timbers like Zebrano, Brown Oak, Wenge and more recently…Thermo Ash.
Thermo Ash, is Ash that has been modified by the process of Pyrolysis (Heat Treatment). Typically, modified woods like Thermo Woods and Accoya are used for external applications such as cladding and decking – and that is because the modification process fundamentally changes the properties of the wood to great benefit.
Wood is by nature, a biodegradable and dimensionally unstable material, but the process of modification changes that. Modified wood has greater durability, resistance to swelling and shrinkage, and increased hardness (and therefore greater resilience to wood boring insects). The acetylation process also reduces moisture in the cell wall to the point where there isn’t enough to support fungal decomposition.
In addition to this, the process of treating the wood at high temperatures (in the absence of oxygen to prevent burning) means that the higher and longer the heat, the darker the wood becomes throughout. This can give native woods, the look of desirable imported timbers.
For our student Mark, the initial attraction to using Thermo Ash was simply that it was a timber that was new to him – but also because he wanted his small occasional table to have a darker colour timber– similar to brown oak or walnut. Thermo Ash fitted the bill nicely. However, the benefits, as mentioned above were also attractive in terms of making a durable and lasting piece of furniture.
Mark found the Thermo Ash easy to work with, and the timber had a nice fragrance. Due to the nature of the wood being dry from the heat processing, the timber can have a tendency to be brittle if being worked on by hand tools, so Mark found that he needed to take extra care when working with hand skills. For the same reason, it isn’t best suited to larger weight bearing pieces of furniture like chairs, but it is perfect for small occasional tables like the one Mark is making.
The process of acetylated wood is quite interesting, and if you are keen to know more, this website gives you a good overview of the process: https://cen.acs.org/articles/90/i32/Making-Wood-Last-Forever-Acetylation.html