Conservation of Thomas Brock’s bust of Frederic Leighton

As part of our ongoing conservation work at Leighton House, we commissioned City & Guilds of London Art School to carry out repair and conservation works on a plaster bust of Lord Leighton.

Sculptor and medallist, Sir Thomas Brock RA (1847-1922), was chosen by Frederic Leighton to sculpt several busts of his likeness, in varying sizes, in plaster and bronze mediums which were given to several leading institutions. After some difficulty obtaining sittings from Leighton, due to his travel commitments, Brock submitted the original bronze bust in 1891 to the Royal Academy – of which Leighton was President. Other bust copies can be found at the National Portrait Gallery and The Royal Collection.

This plaster version was given by Brock in 1916 to The Holburne Museum in Bath, before being transferred to Leighton House in 2008. In this depiction, Leighton is shown wearing his Doctor of Civil Law robes, an honour he was awarded from Oxford University in 1879, as well as the Royal Academy Presidential gold medal.

Here, we interview Louise Davison from City & Guilds of London Art School about the procedures and challenges she faced.

What was the condition of the bust when you started your conservation work?

As well as discoloration and deterioration of the surface layer of the bust, a large corner of the socle (the supporting block used as a base for the sculpture) had broken off. In addition, a textile covered wire fixing which had been added and tied around the top of the socle required removing.

What techniques were used to analyse how you would proceed?

Starting out, analysis of the damage, deterioration and previous conservation efforts was first necessary. This included examining the bust under ultraviolent light and testing of fluorescence (an emission of light only seen under UV light) which would help to determine any breakdown in the coating layer and where it may have been retouched with a different material. For example, the green/yellow fluorescence seen in the UV images could indicate a dammar varnish or mastic resin coating.

Microscopy analysis - where cross section samples are taken and examined under a microscope using visible light and UV light - also helped to determine that the bust does not have a consistent stratigraphy (layering). It was found that the bust and the back of the head have more layers, whereas the lapel and ear have less – this suggests the face has had multiple coating additions. Combined with microchemical testing, it was possible to determine what some of the layers may be compiled of. For example, the detection of protein present could be the result of an animal skin glue in the plaster.

Finally, DinoXscope images taken using a Dinolite (USB microscope) confirmed previous observations that the structure on the surface is not cohesive and highlighted issues that needed addressing in order to conserve and restore the surface of the bust.

How did you repair the broken socle corner?

In order to determine the best approach, tests had to be carried out trialling the results of various fill materials to mimic the plaster, as well as different types of adhesion for the reattachment.

Results concluded that a mould of the loss would be cast with plaster of Paris and rabbit skin glue, attached with PVB (polyvinyl butyral) and sanded, thus exposing the object to the least amount of moisture and creating the best visual match. The addition of the rabbit skin glue also allows future conservationists to distinguish the repair, for future work that may need to be carried out.

What were some of the more challenging aspects of the conservation project?

The cleaning and removal of various marks and discolouration was certainly time consuming. This was a very methodical process, requiring constant observation through the binocular microscope to ensure no paint or plaster was damaged in the process.

Similarly, retouching using golden acrylics required several different approaches, the smaller losses over the surface could be toned with washes, that were colour matched to the area surrounding the loss. The larger areas of raw plaster caused more issues. It required dry stippling on with the acrylic and building up with faint layers of tones, to create a subtle yet cohesive affect.

What might have happened to the bust without this conservation project?

Without this conservation work, the surface of the bust would have continued to deteriorate, including further discolouration and flaking of the painted surface, as well as abrasive damage caused by the wire. Reattaching the broken socle corner has also restored a safe support for the sculpture.

How will Brock’s bust of Leighton be displayed in the ‘new’ Leighton House?

The bust will take pride of place in the display case within our new reception space, when Leighton House reopens in spring 2022 upon completion of our major restoration project, Hidden Gem to National Treasure. The display case will showcase items relating to Leighton’s life and career, introducing him to visitors as an artist and public figure.