20 C O N T E X T 1 6 8 : J U N E 2 0 2 1 SOPHIA MIRASHRAFI and MAUREEN YOUNG Innovation and investigation at the Hill House Innovative digital and scientific methods of documenting the condition of one of Charles Rennie Mackintosh’s best buildings is a prelude to tackling its dampness. The Hill House in Helensburgh, Scotland, is one of Charles Rennie Mackintosh’s greatest and most complete works. However, since its construction at the beginning of the 20th cen- tury, the house has been subject to damp ingress, threatening its very fabric. In an effort to further document and under- stand the complex story of the Hill House, the digital innovation, documentation, and conser- vation science teams at Historic Environment Scotland (HES) have teamed up with the National Trust for Scotland (NTS) to digitally document the site, and complete moisture map- ping and thermographic surveys. These surveys will inform our understanding of how to care for the Hill House, while providing virtual access for professionals and visitors alike. The Hill House, built and designed by Charles Rennie Mackintosh and Margaret Macdonald Mackintosh in 1904, was a bespoke home for the Glaswegian book publisher Walter Blackie and his family. Because of its cement roughcast, chosen by Mackintosh for its aesthetic, price and seemingly waterproof properties, rainwater has entered the fabric through cracks and defects, causing the house to suffer from damp for decades. As the wind-driven rain in Scotland increased over time, the house was in growing danger of becoming irrevocably damaged if no action was taken by those who protect it. To stall the damage to the building, in 2019 the NationalTrust for Scotland built a protective box round the house. Made of chain-linked steel, the box lets the house dry out slowly with- out being pelted by wind-driven rain. The teams at HES were called to perform several surveys, building on some earlier investigative work that the NTS had previously commissioned. The science team at HES used two methods to investigate moisture distribution at Hill House: thermography and microwave moisture meas- urement. The first provides information about the near surface of the building and the second looks deeper below the surface. Infrared thermography Thermography uses thermal cameras to detect infrared light emitted by objects. The intensity of infrared emissions is related to surface tem- perature, effectively providing a temperature distribution map of a surface. The Hill House in its protective box Colder (blue) areas on the thermal image show elevated moisture levels behind the harling.