‘A Stitch in Time – Guidance Notes in Maintaining your Place of Worship’

Guidance Note 5 – Stained Glass Windows

This guideline explores issues relating to historic stained-glass windows in Churches. It will cover the following range of topics:
  • Character and artistry
  • Light and ventilation
  • Heat and Cold
  • Security and protection
  • Maintenance and repairs
  • Managing change.
Windows are important in defining the character of historic buildings, particularly of churches. Many of those who worshipped in churches in the Middle Ages were unable to read and church windows provided a pictorial representation of stories from the Bible. Stained glass reached levels of breathtaking artistry, not only in the decoration of the glass itself but also in the structural form of the windows themselves, in the Gothic church of Sainte-Chapelle in Paris.
Sainte-Chapelle, Paris.
Church windows were also intended to provide natural light, and often also ventilation to interiors. Victorian-era churches did not consider the comfort of worshippers to the extent to which we do now-a-days, so often there was little allowance for fresh air vents. As a result, many crude and ugly opening sections were fitted retrospectively into stained glass windows that often weakened their structural integrity.
Leaded glass in poor condition in a ventilation hopper to an Adelaide church. Image thanks to The Glass Foundry Leadlight Designs.
Historic church windows are generally large and, of course, made from single layers of glass. This means that they are relatively poor at keeping in heat, tending to generate cold down draughts in the winter. They also encourage heat build-up in warmer months. The use of secondary glazing, either on the inside or outside, especially were solar-control glass is used, can involve the environmental performance of large windows but it is expensive to fit.
Poorly fitting mesh protection to an Adelaide church. Note the fixings directly into stonework.
Stained glass window to an Adelaide Chapel viewed from inside.
The same window as above but viewed from outside. The protection glazing has gone cloudy over time.
Another good reason to fit secondary glazing to church windows is for security and protection. Where stained glass is prone to be a target for vandals’, protection is fitted over the outside of windows. This usually takes the form of either metal wire mesh grilles or clear plastic sheeting. Due to the historic significance of older churches careful consideration needs to be given to the specification, design and installation of this type of window protection. Grilles and fixings into masonry are best made from stainless steel, and fixings should be into joints rather than into the masonry itself. Older, clear acrylic plastic sheeting tended to go cloudy over time while current clear polycarbonate sheeting maintains it’s clear appearance for much longer.

Stained glass is surprisingly strong and flexible, despite being made from small pieces of glass held in place by lead ‘cames’. Skilfully designed stained glass windows can last for many hundreds of years, but even the best windows will eventually require maintenance. Lead degrades over time, especially in a polluted environment. The metal oxidises, evidenced by white chalky deposits on the surface, and as a consequence it becomes weaker and is prone to tear and stretch more than fresh lead. Pigments used on ‘stained’ or painted surfaces will fade and sooner or later every stained-glass window needs to be repaired. As far as maintenance is concerned, windows should be inspected annually and any signs of wear and tear should be dealt with quickly to prevent escalation. Little maintenance is generally required to healthy, and well designed and constructed stained glass. Depending upon how exposed stained glass is to vehicle and/ or industrial pollution, it should be carefully cleaned perhaps every 20 years or so inside and out very gently only using deionised water to remove contaminants.

If a church congregation wishes to alter their historic stained-glass windows a valid case could well be made for doing so, but changes must always be made in the context of the significance of the church as a whole and it is essential to seek professional advice from an experienced heritage architect who can assist greatly in managing such change.

If you are in any doubt about the condition of your stained glass, or of your church building in general, please don’t hesitate to contact Arcuate Architecture and we would be delighted to assist you.

Ian Hamilton, Director
Arcuate Architecture, Adelaide

Website: www.arcuatearchitecture.com.au
Email: ianh@arcuatearchitecture.com.au
Phone: (08) 7231 5701