CONTEXT 181 : SEPTEMBER 2024 33 BELLE NEILSON The architectural use of wood and coal tar in England New research for Historic England has helped to fill the gap in the long history of wood and coal tar being used as materials to preserve, waterproof and decorate buildings. Wood and coal tar have long been valued as building materials for their preservative, waterproofing, adhesive and decorative properties. They are principally recognised as timber treatments but historically found diverse applications across various substrates. A keyword search of listed buildings in England returns 1,129 examples that include tar in the list description, and there will be many others where this material has not been explicitly identified, along with countless unlisted examples. Nevertheless, there has been limited research on the architectural use of tar and addressing this lacuna becomes more pressing as the heritage industry moves away from coal tar due to carcinogenic and environmental concerns. This article summarises a literature and archival review commissioned by Historic England on the architectural use of tar in England across history. It has been undertaken with the assistance of Michael Knights, a retired planning and historic building advisor, and leader of the Norfolk Wood Tar Project.1 Tar is a brown or black viscous liquid obtained from the destructive distillation of wood or coal. The chosen material is heated to a high temperature with limited oxygen to break the heavy hydrocarbons into smaller molecules, resulting in three main products: tar, gas and charcoal or coke. The terms ‘tar’ and ‘pitch’ are often used interchangeably, but the latter is made by reducing tar and has a considerably higher viscosity. Historically, pitch has been favoured as a building material due to its more solid and adhesive nature compared to unrefined tar. A vast number of chemicals can be extracted during the distillation of wood and coal, with a notable substance being creosote, Net and tackle stores on Hastings beach (Photo: Toby Crisford, Wikimedia) 1 Knights 1999
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