When the stained-glass windows have been removed, the gilders conduct a preliminary cleaning operation in order to define the zones for intervention. Each window is unique: the state of preservation of the gilding, the deterioration of the gold and any lacunae are very random, depending on the location of the windows, their exposure to light, wind and humidity. In order to conduct their intervention and thus preserve the existing gilding as much as possible, the gilders treat each window individually. On the interior part, the priority is to identify the most fragile zones in order to consolidate them.
After consolidation, the remaining non-adhering parts are removed delicately by sanding, in order to restore a healthy base. This operation may seem excessive, but the preparation of the base must be perfect in order to render the gilding long-lasting. The gilders are in charge of removing dust from the iron windows where the gilding has blackened with time. They then fill in the parts where the gilding has flaked. This part is known as "preserving old gold". On the exterior part, no preservation is possible. In fact there was no gold left before the sanding, only black paint. The sanded base is thus completely re-gilded. The base is prepared with several layers of paint and varnish, the gilders then apply a mix that will enable the gold leaf to adhere to the surface.
The gilders' work is very visual, giving them a leading role in the restoration of the Royal Chapel. After restoring the windows, the gilders will gild the sculpted lead décors on the roof.
