The stained and leaded panels from the “Life of Christ and the Virgin” window have now been assessed in the studio. We have taken images from the front and back in transmitted and in reflected light which records the maximum amount of information about the condition of each panel.
One of the most immediately obvious things about the panels from this window is that all the lead has been tinned. This means that molten tin has been applied and is covering the surface of the lead cames.
Why would this have been done?
Tin is harder than lead, so usually tin is applied to lead that is too soft and flexible – and therefore not giving enough rigidity to the panel.
Could it have been applied in 1881 when the panels were restored in Berlin in the Royal Institute of Glass Painting?
I think this is very unlikely. It looks like the panels were completely re-leaded during this restoration and I would be surprised if the restorers would have tinned a newly leaded panel. It is more likely that the new lead was very pure – and therefore very soft. It was also probably very insubstantial with thin cores and flat flanges. So I assume that sometime perhaps 40 or 50 years later, they were tinned to make them stronger and more rigid.
It is possible that the tinning of the lead was carried out while the panels were in the United States in the collection of the newspaper magnate William Randolph Hearst. Tinning copper foil to make stained glass windows and other decorative artefacts such as Tiffany Lamps was an invention made in the USA in the late 19th century. Stained glass restorers there would have been familiar with tinning as a technique to be used to strengthen a panel.
In the coming months I will explore this issue as I progress with further assessments. The most obvious investigation will be to find an area of accessible lead where I can take a sample to analyse and find out if my theories are substantiated by what I find.