Historic Churches 2019

18 BCD SPECIAL REPORT ON HISTORIC CHURCHES 26 TH ANNUAL EDITION For a small church like St Leonard’s with limited funds, where the cost of environmental monitoring can prove prohibitive, other means of assessing the conditions may provide sufficient evidence of an ongoing problem. We humans come equipped with inbuilt temperature and RH sensors: although not very accurate, we can tell on walking into a church if the air feels cold and damp and there are usually visual indicators to corroborate. In this case the north and east windows both had healthy, green algal colonies on the inner painted face of the glass (illustrated on the previous page). Algae need a damp or wet environment to survive, so if there is green algal growth on a surface, it’s reasonable to assume that regular wetting is occurring. EPG was therefore recommended for the two north windows and the east window. EPG design From a design perspective, installation of EPG to the north elevation was not problematic as the churchyard to the north is unused and the windows face a field, so large economical sheets of toughened float glass could be used for the external glazing. The stained glass was retained in its original position with vents fitted at the heads and bases and the external glazing was fixed to the external reveal, sealed with lead at the perimeters giving an interspace of 50mm. Installation of EPG to the east window needed careful consideration. The car park lies to the east of the church and the first view most visitors have will be of this elevation. Indeed, the path leads you right past the east window as you approach the south door. It was decided that the EPG should mimic the external appearance of the stained glass; that is to say that it should be leaded, following the major lead-lines of the stained glass. Rubbings were taken of the existing lead matrix and unpainted areas noted so that parallax adjustments could be made. Glass samples, painted and unpainted were taken to site and compared to the window surface and a sample leaded panel was made, again for comparison on site before EPG design was finalised. After close comparison, kiln softened horticultural and antique glasses were lightly painted to mimic the appearance of the stained glass. The stained glass was removed for careful cleaning and to install vents at the heads and bases before being re-fixed in its original position. The leaded secondary glazing panels were fitted to the external reveal with an interspace of 50mm. Post installation monitoring has taken the form of site visits and observation. It has been gratifying to find the EPG running wet and channelling water to the outside of the building while the historic glazing remained dry. However, the success of the project owes much to the churchwarden, Angela Yeoman and the PCC and to the church’s inspecting architect, Marcus Chantrey of Benjamin and Beauchamp Architects. DAN HUMPHRIES studied architectural stained glass at the Swansea Institute of Higher Education, now Swansea Metropolitan University, graduating BA(Hons) in 1997. He trained in stained glass conservation under Steve Clare at Holy Well Glass, setting up his own practice Dan Humphries Stained Glass (dhstainedglass@gmail.com ) in 2015. He is an accredited conservator restorer (ACR), sits on the Glaziers Trust and the Icon Stained Glass Group committees. The completed EPG to the east window at St Leonard’s, Marston Bigot, and (right) a detail of the 16th-century stained glass just behind, seen from the inside