Two special edition pieces exploring alternative wood treatments for outdoor furniture.

Wood is inherently a biodegradable and dimensionally unstable material. These characteristics present problems such as rotting and warping, issues which become increasingly challenging to manage when designing for outdoor environments. The Tanso Editions have been designed in a bid to overcome these challenges through the application of two different timber treatments. The oak bench has been finished using the ancient Japanese technique of charring wood, ‘Shou-Sugi-Ban’, and the chair is made from beech that has been thermally modified by heating it in an oxygen-free environment. Both treatments improve the timber’s climatic resistance and dimensional stability to the highest ‘Class 1’ durability*.‍

*Timber Durability is measured in 5 classes under the EN350 classification system, with each class determining how long each timber will survive outdoors. These range from class 1 – very durable, lasting 25+ years, to class 5 – perishable, lasting less than five years.‍

The Japanese practice of ‘Shou-Sugi-Ban’ dates back to the 1700s. Traditionally, Sugi (Japanese cedar) was used. However, the same results can be achieved in most open-cell species. The process involves charring the wood, cooling it, cleaning it, and finishing it with natural oil. It works by applying fire to the wood’s surface for a short period. This burns off the softer, cellulose parts of the timber, leaving the harder areas of lignin behind. The remaining charred layer of lignin protects the wood from UV and weathering and is much more fire-resistant (the more combustible cellulose having been removed). Carbonising removes nutrients and sugars commonly eaten by insects and rot-producing fungi. Timber treated in this way can last more than 80 years.