Historic Churches 2019

BCD SPECIAL REPORT ON HISTORIC CHURCHES 26 TH ANNUAL EDITION 23 renders it particularly susceptible to condensation damage (underfired Victorian glass is a notable example); or • the stained glass is so significant that no further loss, however slight, is acceptable; or • there are good conservation reasons to avoid dismantling the window for repair (such as the risk of damage, or the wish to retain early and important leading); or • the window is very inaccessible (and unusually difficult to inspect and maintain). It is sensible to undertake an options appraisal that considers all the potential impacts (good and bad) in some detail before deciding whether EPG is the correct intervention for delivering the aims of a stained glass conservation project. This appraisal will need to include: • the significance of every component that might be affected by EPG (the glass, the lead net, the stonework and the ferramenta) • the contribution made by each component to the viewer’s aesthetic appreciation of the window (from both the interior and the exterior) • the condition of all those components, and the nature and rate of their deterioration • the potential positions of the two glazing planes within the depth of the window embrasure. What possibilities are afforded by the profile of the embrasure, and what would be the aesthetic impact of the glazing planes on the window, considered in the context of the building as a whole? • how the windows (including those where it is not proposed to use EPG) contribute to the building’s architectural design, historic interest and aesthetic character. Aesthetic success will depend largely on the design and materials of the protective glazing. Well-designed EPG can and should be all but invisible, even to a knowledgeable viewer. The new Historic England guidance note gives extensive guidance on this aspect of EPG. The primary contributor to designing effective and sympathetic EPG will be the stained glass conservator, who should have ample experience adopting EPG to suit many different situations. They will need to work closely with the stakeholders, and perhaps with other specialists such as stone conservators and metal conservators. In difficult cases, it might be necessary to speak with a building performance expert, who can suggest ways of assessing the in situ conditions, and the effectiveness of the EPG design. Sensitive design will greatly reduce the impact on the building, but since EPG should only be used where there is a demonstrable need for it, design should never trump the effectiveness of the system. If EPG is required, then the principal design criterion must be that it can do the job being asked of it. Further Reading T Curteis and L Seliger for Historic England Research Report, Conserving Stained Glass Using Environmental Protective Glazing , London, 2019 Historic England Guidance Note, Stained Glass Windows: Managing Environmental Deterioration , Historic England, Swindon, 2019 English Heritage, Glass & Glazing: Practical Building Conservation Series , Routledge, London, 2011 English Heritage, Building Environment: Practical Building Conservation Series , Routledge, London, 2014 ROBYN PENDER PhD is a physicist with a degree in wall-painting conservation and a PhD from the Courtauld Institute of Art. She works for the Technical Conservation Department at Historic England (conservation@historicengland.org.uk) and is a commissioner on the Cathedrals Fabric Commission for England.