C O N T E X T 1 1 7 : N O V E M B E R 2 0 1 0 7 still empowered by the terms of the Theatres Trust Act(s) to promote the better protection of theatres for the nation. The culture secretary will transfer the power of appointment of the trust’s trustees to the Theatres Trust itself. It will take over responsibility for trustee recruitment from the DCMS public appointments unit. At least for one valued body it appears it is business as usual. The announcement that the DCLG will replace regional development agencies (RDAs) with local enterprise partnerships means that local authorities and others will need to regroup and make new alliances. RDAs which had been so supportive of heritage-led regeneration (most notable among them being the North West Regional Development Agency) will be missed. Policy is essential to support protection. In this issue, Rose Freeman, the trust’s planning policy officer, has marked the receipt of the trust’s 3,000th (yes really!) local development framework consultation to synthese the way in which spatial policies secure the protection of theatres. She reports on her work and how local authorities have adopted the trust’s suggestions and recommendations. Turning to weighty matters further afield, the Association for Preservation Technology’s APT Bulletin (Vol 41, Nos 2–3 2010) continues to demonstrate outstanding technical work being done in North America, while also highlighting projects in Sweden and, through UNESCO, in Asia. The Swedish study is by Emma Hocker, who describes a very out-of-theordinary scheme: the extensive upgrade to the air-conditioning of the Vasa Museum in Stockholm, helping to preserve the largest and best-preserved wooden warship ever salvaged from the seabed and conserved. The ship sank on its maiden voyage in 1628, was salvaged in 1961 and, after 26 years of conservation, moved to the purpose-built museum in 1988. The internal airspace of the museum is 105,000 cubic metres. The exhibition areas, although air-locked, were generating an unstable climate which the new climate-control system has rectified, despite the huge volume of air involved. This is probably one of the largest internal public spaces in the world maintained to such a close tolerance. The solution is a major conservation achievement. The scientific investigation of bright, unsightly, red staining on white marble at the Memorial Amphitheatre of 1920 at the Arlington National Cemetery in Washington is the subject of an evaluation by Carol Grissom, Claire Gervais, Nicole Little, Genevieve Bieniosek and Richard Speakman. Such staining of marble, documented in Italy as early as 1844, was initially ascribed to biological sources, but research 25 years ago concluded that it was caused by the oxidisation of lead derived from its use for roofing, gutters and so on. Alkaline mortar, acidic water, atmospheric agents and microorganisms were also proposed as contributors. The article illustrates this phenomenon in colour, explaining in detail the recent scientific process of analysis. This definitively proves lead to be the culprit. Preventing staining requires the elimination of any of the elements necessary for its formation: excess water, lead and high alkalinity cement mortar. The report warns that methods of remediation, apart from overpainting or replacement of the affected stone, are unlikely to be successful. Conservation of modern materials in 20th-century historic buildings is the subject of two articles in this issue of APT Bulletin: matters which will become of increasing concern as more modern buildings such as those at Leeds and Milton Keynes become protected. Laura Buchner describes the restoration of Akoustolith ceiling tiles (a 20th-century acoustical-finish material) at the Cathedral Church of Saint John the Devine in NewYork, which are a significant component of the interior finishes. The article outlines the history of the material; how it was incorporated into the building; and how it was cleaned and stabilised following a fire in 2001. The author emphasises the importance of gaining a full understanding of the properties of the material though archival and laboratory research to ensure sensitive repair. The second article looks at the conservation of architectural cast Pyrex glass, a material, usually associated with cookware, which presents its own special conservation problems. Mary Jablonski gives a brief history of the production of the material which, despite some experimental antecedents, commenced in 1915, with panels for architectural work made in the early 1930s. One of the best examples – illustrated in the article – is at the Rockefeller Centre in New York. Of the lessons learned from the conservation project, the author stresses how complex the decisions about conservation treatments can be. They are potentially further complicated by a lack of information on such ‘modern’, if transiently used, materials. Those concerned with the fire protection in historic buildings will find the article by Douglas Porter and Nick Artim of interest. It explores the application of the latest technology in designing and installing fire detection and fire suppression systems to a mid-18th-century California property on the register of National Historic Landmarks. This involves some clearly explained and sensitive interventions. Another article by James Mellett and Shelley Smith looks at the non-invasive techniques, namely the use of groundpenetrating radar as a powerful tool for discovering voids and deteriorating mortar in masonry buildings. The two associated case studies demonstrate that this technique can also verify the success of injection-grout remediation of stone walls, which is especially useful for areas of honeycombed mortar that retain water after heavy rain. The authors argue that wholesale grouting and repointing may not be necessary if the major source of water infiltration can be addressed. The central eight-page pull-out Practice Points section gives advice on non-destructive evaluation in relation to the structural performance of masonry. The section gives detailed tables of appropriate test methods to evaluate or investigate various masonry conditions, and the (American) standards for nondestructive evaluation and in-situ tests. The final article illustrates the developing consensus about powerful ‘first principles’ behind award-winning UNESCO projects. Although anchored by international standards, these reflect
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