So quickly we reach our final ‘this is heritage science’ post of BSW16. Here Dr Ewan Hyslop, Head of Technical Research and Science at Historic Environment Scotland contributes directly from Beijing. He writes about his current visit to establish joint research with Chinese heritage scientists from the Palace Museum in the Forbidden City, Beijing. Identifying potential areas for collaboration and exchanging knowledge and expertise on aspects such as digital documentation using laser scanning and 3D modelling to assist understanding of objects and structures, identification of stone types and mortars, understanding the performance of historic brick and tiles, plasters and paints.
The Forbidden City is the former imperial palace in the heart of Beijing, constructed between 1406 and 1420. It extends over a million square metres and has 1.8 million objects in its collections. It has seen an increase in visitors from 7M to 15M over last few years, making it the most visited museum in the world. There is a need to balance conservation of the site with the pressures arising from providing access –potential for damage- and heritage science has a role to play in helping make improved decisions on the conservation and management of the site and its contents. Some days there are >120,000 visitors, whereas capacity is 60,000, resulting in pressures on the ancient structures and the collections. A new conservation centre is due to open in October 2016 with a staff of over 100 conservators and heritage scientists.
This initial visit involved meeting heritage scientists and discussing common issues where cooperation may provide mutual benefits. One of the interesting aspects coming out is the use of glutinous or ‘sticky’ rice in the lime mortars in China, this was reputed to have been developed as much as 1500 years ago and used for the construction of some of China’s most iconic structures. Recent chemical studies have confirmed the presence of rice and identified a particular compound –a polysaccharide called ‘amylopectin’ which inhibits the crystal growth as the mortar cures, creating a particular compact microstructure that protects the material from weathering and improves performance. The confirmation of the secret ingredient that gives the mortar its legendary longevity has meant that recent conservation works have used mortars containing sticky rice to protects the iconic monuments in the Temple of Heaven that dates from the 1530s.
Further information on sticky rice mortar can be found at: http://heritagesciencejournal.springeropen.com/articles/10.1186/2050-7445-1-26