Historic Churches 2021

30 BCD SPECIAL REPORT ON HISTORIC CHURCHES 28 TH ANNUAL EDITION MEASURING IN 3D New approaches to digital measuring for stained glass at the York Glaziers Trust Nick Teed and Zoe Harrigan T HE TAKING of accurate dimensions and templates of stone or timber window openings has long been one of the most critical aspects of a successful stained glass project, whether a window is to be removed for studio conservation or a new commission is to be created. It is essential that any window forming the weather shield for a building is well fitting, secure and weather-proof. With the help of a good template, a previously ill-fitting window can be improved with simple remedial measures such as the addition of extra lead at the perimeters. Environmental protective glazing (EPG) is also frequently used to prolong the life of historic stained glass exposed to decades or even centuries of wetting and drying cycles, which promote deterioration of both glass and painted detail. The development of these complex glazing systems relies on an array of accurate dimensions to aid in the design of an installation appropriate to the profiles of a specific window structure. With this in mind, the team at the York Glaziers Trust (YGT) was keen to discover whether new technologies were available to complement or even replace traditional methods of creating paper or card templates of complex window shapes, while also improving on the accuracy and speed of execution. TRADITIONAL TECHNOLOGIES For many years, staff training at YGT has included the best traditional methods for plotting the glazing plane in often complex window openings. These rely on accurate readings of tape measures which take account of glazing bar positions, followed by the preparation of carefully cut out paper templates for architectural canopies or window traceries. For the glazier, these measurements are most useful at the visible stone edge between the mullions or tracery openings, often referred to as ‘sight size’. With this information, the glazier can determine precisely how much lead should be allowed to set into the glazing groove and how much should be visible outside the groove (normally a case of half the perimeter lead showing and half within the groove). In recent years YGT’s team has started to use digital laser measuring tools, which have proved to be affordable, accurate and convenient for straight dimensions. However, paper or card templates continued to be essential for shaped openings. Following a number of projects that contained significant quantities of shaped traceries (for example, the conservation of the Great East Window at York Minster, and the East Window of Lincoln College Chapel, Oxford) the team began to explore whether other options were available. This research was greatly facilitated by a new initiative supported by the York Minster Fund, securing the technical expertise of engineer Laura Cotter, who has worked with both the Conservator Zoe Harrigan measuring the profiles of a window (CHn5) in the Chapter House Vestibule of York Minster in 2021 (All photos: York Glaziers Trust)