~ Scottish National War Memorial Shrine, Edinburgh Castle ~
Following a few years of regular maintenance inspections, it was arranged in 2020 to re-waterproof the exterior of the SNWM Shrine windows after leaks were reported by the Castle staff. Unfortunately, COVID meant that the Castle was closed to all but essential staff, and the work was delayed for over a year, until April / May 2021.
The beautiful windows by Douglas Strachan are almost 100 years old, and in really very good condition. However, the putty inbetween the lead and the glass, and that on the internal T bars, had dried, fallen out and was missing in many places due to the extremes of weather at the top of the Castle mount.
Old dry putty on the T bars was chipped out and replaced by new fresh linseed oil putty. Where it was stable, it was re-rejuvenated by brushing with raw linseed oil, which was allowed to seep into the existing putty. When dry, all the bars were painted with dark grey oil paint. There was evidence that this had been done previously.
A new thick, runny putty mix was made up, using raw and boiled linseed oil, whiting, white spirit and lead black. This was carefully rubbed into the gaps inbetween the lead and glass with a toothbrush, until all the gaps were filled and sealed. The entire surface of glass and lead were then further rubbed and brushed dry until polished.
On one window, the lime mortar had failed and cracks could be seen down each side next to the stone. After discussion with the HES District Architect, with various treatment options, it was agreed to remove the loose surface of powdery mortar, and to re-coat the surface with a stickier, oil-based resin mix, which would help bind the mortar back onto the lead, but in a thin enough coating to be easily removed. The same treatment will be applied to the internal sides once access is provided.
Hopefully, by regularly maintaining the weatherproofing on these windows, they will be good for another 100 years and more.
My thanks to Vivienne Kelly and Robin Cannon for their assistance.
