C O N T E X T 1 4 2 : N O V E M B E R 2 0 1 5 7 Periodically Another quiet spell for the publication of heritage journals has resulted in a shorter column than usual this time. The summer issue of the Association of Preservation Technology Bulletin is always a double one. The latest (Vol XLVI, Nos 2–3, 2015) is wide ranging it its content, after several recent editions have been devoted to the conservation of metals. Although there is earthen vernacular construction in many parts of Britain, this is usually small in scale. So it is fascinating to read a description and history of an earthen building on the grand scale: the Djenné Great Mosque in Mali, on the world heritage list since 1988 and defined by the French as in the ‘Subanese style’. Trevor Marchand explains how the exterior is maintained on an annual basis (with photos that would have any UK health and safety official in shock). He explains the regrettable impact of fractious regional heritage and religious politics, and what these mean in terms of the challenges for preservation that the local community must face in the light of external advice and interventions. Turning to more technical issues, Lizzie Olson and Derek Trelstad discuss the deterioration of 19th-century masonry structures affected by harsh marine environments by using the example of Fort Jefferson in Florida, built between 1846 and 1875. Buildings of this type rely for their structural integrity on geometry, proportion, and the quality of the materials and original construction. If properly designed and built, the actual material stresses within unreinforced masonry are less to do with the materials than the design. The authors describe the programme of testing, analysis and monitoring carried out in 2013 to understand the fort designer’s original intentions. They evaluate the condition of the masonry structure using field measurements, traditional graphic analysis, and modern finite element and thrust-network analysis, with in situ and laboratory testing of the materials to determine acceptable levels of deterioration and the works necessary to maintain the stability of the structure. Documentation plays an important part in guiding strategies for the appropriate conservation of important sites. Ilene Tyler describes how this was carried out at the Highland Park Ford Plant in Michigan. Numerous innovations in car mass production were developed there between 1910 and 1926. It was the birthplace of the moving assembly line, and the noted architect Albert Kahn designed a number of the distinctive buildings in reinforced concrete and brick that are characteristic of his industrial work. The article is well worth sourcing for its description of how large redundant and semi-derelict industrial sites can be assessed; how a resulting cultural resource management plan aims to guide rehabilitation and adaptive reuse; and how a historic structures report documents the existing condition and proposed future treatment of the most intact but most vulnerable buildings. Although few derelict, historic, industrial sites on this scale exist in the UK, the described methodology merits reading as a guide to the rehabilitation of large, challenging sites where important abandoned heritage buildings and structures remain standing. Carolyn Andrews has produced a paper on the repair of a major doubledeck trunnion bascule bridge across the Chicago River, completed between 1916 and 1921. At the time this was the longest and heaviest two-truss bridge in the city. The bridge has been exposed to harsh environmental conditions, including the use of winter road salt and high traffic loads. Rehabilitation of the bridge began in 2008. Andrews describes in detail the engineering assessment, the removal of inappropriate or ineffective later alterations, the reinstatement of historic detailing, and the repair and cleaning of the stone bridge-houses and stonework abutments. She emphasises the importance of aiming for long-term restoration results and the need to ensure that the role of the conservation architect is not marginalised within a largely engineering-based team. There are a number of lessons from this example that could be applied elsewhere, not just to similar bridges but also to the professional interpersonal dynamics of multi-disciplinary projects. In my March 2015 review of the Association of Preservation Technology Bulletin I referred to the conservation of dalle-de-verra panels used on the New York Hall of Science for the 1964–63 World’s Fair – one of its few permanent surviving mid-century landmark buildings. The cobalt blue glass panels were set within reinforced concrete frames. Two of the authors of the earlier paper, Raymond Pepi and Laura Buchner, describe the approach to the repair of the cast-in-place reinforced concrete coffers, and how field and laboratory testing led to the repair approach adopted. The conservation of historic interior finishes does not appear very frequently in the Bulletin, so it is a pleasure to recommend a paper by Claudia Kavenagh and Raymond Pepi about the restoration of two aesthetic movement rooms at the huge Seventh Regiment Armory in NewYork City, completed in 1880 to the designs of Charles W Clinton and containing interiors by
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