The staircase balustrade after conservation. Photo kindly provided by the Royal Institution
Between 2006 and 2008 the Royal Institution's Grade I Listed, Georgian headquarters in Albemarle Street underwent extensive refurbishment. We were commissioned to conserve the staircase balustrade, which is predominantly made of wrought iron, with lead and bronze castings incorporated into its design. The balustrade has a repeating pattern of 66 sections, each with the same leaf and flower design.
The staircase balustrade before conservation
Before conservation, the structural condition of the metalwork was fair. However there were significant areas of loss to the repeated design where lead and sometimes bronze had been used in the past to replace lost pieces. The whole balustrade had been painted black with the exception of the flowers, which were painted gold - many layers of paint rendering the detail of the metalwork indefinable. Importantly, paint analysis was carried out before any treatment began, to establish its decorative history.
Given that the original colour layers were well documented by the paint analysis, a decision was made to remove all the existing paint back to the bare metal. Cleaning tests were carried out using a caustic poultice, this proved successful and although time-consuming and potentially messy (as can be seen in the photographs below) was, with care, controllable and avoided significant fumes.
The painted stone steps were masked to protect them from the treatment. After a section was fully coated with paste it was covered with a thin sheet of tissue paper and we also wrapped tissue around the footings to absorb the dripping paint.
Careful wet cleaning was then carried out to remove all residues of poultice and paint, then mechanically cleaning the metalwork with wire brushes to clean the metal to a standard where it could be re-painted.
There were several areas of lost elements on the balustrade. Complete, existing castings were taken from the Royal Institution site, stripped of all their paint, moulded and re-cast. All the new castings were made of bronze. We then finished the surfaces and sanded them smooth and attached the new castings and the original patterns onto the balustrade using tin-silver and lead solder where necessary.
Following the results of the paint analysis and after careful consideration and discussion of the practical issues involved, a curatorial decision was made to paint the balustrade in a later, non-original decorative scheme. The colours used were matched as closely as possible to those that the paint analyst described. The primer layer was a zinc phosphate based paint, pale grey as per original. The green and yellow colours were produced by Papers and Paints Ltd. London.
Photo credit: John Deehan, Photographer, kindly provided by the Royal Institution