Context 154 - May 2018

C O N T E X T 1 5 4 : M A Y 2 0 1 8 13 WO R K I N G W I T H L I M E A N D S T O N E Working with lime and stone This issue of Context focuses on current issues concerning the conservation of masonry structures. Using stone successfully in building conservation depends on understanding the rich diversity of England’s geology, and having accurate information about the original quarries and the buildings constructed from them. ClaraWillett and Chris Wood (page 14) introduce the Strategic Stone Study, Historic England’s county-by-county survey which identifies building stones used nationwide, and maps their sources and representative buildings and structures. Emily Harper and Sue Penaluna (page 17) describe how, even within environmentally sensitive areas, it has been possible to achieve planning permission to reopen two historic building stone quarries for the repair of Exeter Cathedral. David Odgers (page 20) writes about developments in stone consolidants, showing that they have a role as a treatment of last resort, to be used only after other options for slowing the rate of deterioration have been considered. Over the past 40 years the story of lime in conservation has had many twists and turns. After a long period of calmwhenmost people in the industry thought that the issues were settled, and that mortars for the repair of historic buildings could be specified with confidence, modern assumptions are being challenged. Alison Henry (page 30) – who we thank for her help in commissioning the articles in this issue of Context ) – writes that concerns about the strength of natural hydraulic limes have triggered renewed interest in traditional mortars, and in hot-mixing in particular. Conservation engineers Michael Beare and James Miller (page 23) provide an overview of the role of mortar and its constituents in masonry, and point out that strength is rarely a significant requirement. And Jessica Hunnisett (page 26) advises specifiers on mortar analysis. Used correctly, she writes, the analysis can provide a useful tool in the development of a specification. At worst, it may lead to inappropriate specifications being accepted. Finally, theatre-going readers, among others, will be reassured to read the outline by John Stewart (page 34) of good practice in inspecting historic fibrous plaster ceilings. Once again, investigations and research are pushing lime technology rapidly forward, and everyone involved in conservation needs to keep abreast of the outcomes.