Historic Churches 2021

32 BCD SPECIAL REPORT ON HISTORIC CHURCHES 28 TH ANNUAL EDITION Once a drawing is complete, the file is saved and the unit can be moved to the next window. Very large shapes, which cannot be measured from a particular position due to obstructions such as scaffolding, can be measured in stages. To ensure the template’s continuity, each stage (or ‘leap’) is linked together by including a fixed object which can be measured from each tripod position. The files created by CMM are simple linear drawings, which can then be exported to CAD or Adobe Illustrator software for further development or use, or they can be exported as PDF files for stand-alone printing. During the demonstration by Prodim, we were able to quickly and accurately record the shapes and dimensions of several complex tracery sections of the stone surround of a Chapter House Vestibule window which was undergoing conservation at that time. We were immediately able to compare the results with our traditional paper templates, and were very satisfied that the improved levels of accuracy claimed for the unit were absolutely justified. Since our decision to invest in a Proliner device we have continued to expand on its use and found it to be a tool which provides a multitude of functions from the original measurement file. Using the touchscreen on the unit a template drawing can be adjusted to include offsets for frame sizes, glass cutline sizes, and full leaded panel sizes. This allows one drawing to serve a number of purposes, saving time and material costs in comparison to making several hand- drawn templates. Our own preference is to then export the measurement file into Adobe Illustrator where it becomes the starting point for drawing a protective glazing cutline or a frame pattern, which can then be printed 1:1 on a large format printer. In this software, images of the stained glass panels can be combined with the CMM data at full size to use as a guide during conservation, effectively taking the place of a panel rubbing. This is particularly useful when additional leads may be required to bring a loose- fitting panel up to size and shape. The simultaneous use of these different elements within the same drawing allows us to streamline our working processes. It ensures that the design of the protective glazing system fully matches the stained glass on which it is based, and that both will fit extremely accurately within the masonry of the window opening. CONCLUSION There are a number of ways in which modern technologies can assist in gathering accurate dimensions for conservation work on historic buildings. Many of these technical instruments require a measuring or data gathering stage, followed by an in-depth processing of file data in dedicated software. This is particularly the case with 3D scanning technologies, which can create extremely large files and require a detailed knowledge of the software applications. Our own research confirmed that 3D scanning captures a great deal of visual data on window frame shape and appearance, but our specific requirement was a focus on the recording of accurate size and shape above the need for visual 3D interpretation. Furthermore, we had no need to gather information from a remote distance since template making is usually carried out from a scaffold. This simpler set of requirements determined our decision to invest in the Proliner, which is first and foremost a measuring tool. The small file sizes, ease of use of the device, and the accuracy and versatility of the resulting files make this a valuable asset to our working practices within the field of stained glass conservation. Having accurate templates of the stonework in a digital format also means that we can preserve this information for future generations of conservators, while minimising the need to store significant quantities of paper templates and drawings. NICK TEED is an Icon-accredited conservator with over 20 years’ experience at the York Glaziers Trust, most recently as Conservation Manager. He is an associate member of the ICOMOS/Corpus Vitrearum technical and scientific committee, and a member of the Church Buildings Council’s stained glass committee. ZOE HARRIGAN completed her MA in Stained Glass Conservation and Heritage Management at the University of York in 2015, following a BA in History of Art at the University of Leicester. She has over five years’ experience working as a conservator at the York Glaziers Trust, and has taken a key role in digital technologies and their use in the development of protective glazing systems. A CMM drawing worked up in Adobe Illustrator shows the proposed panel position and the frame position according to the stone profile of a window in Merton College Old Library, Oxford.