Conserving the Tondo

by Robert Entwistle, PACR, and Carrie Willis, Conservation Technician

Background

The marble relief Tondo by Michelangelo belongs to the Royal Academy of Arts in London. It is the only original Michelangelo in Britain. Here at Ipswich Museums we have a cast of this relief made in plaster. The Tondo is a circular composition depicting The Virgin and Child with the infant St John.

In 1898, Ipswich Museum, bought 16 casts from D Brucciani and Co. Domenico Brucciani was born in Lucca, Italy and migrated to England in the first half of the 19th century. After establishing a business producing casts, he created a showroom near Covent Garden where he sold works to the British Museum and the South Kensington Museum, now the V&A. By 1857 D. Brucciani and Co. were working for the British Museum making moulds and casts of their classical sculptures, bronzes and other pieces, to be sold commercially.

Following his death, D.Brucciani’s company was purchased by another Italian, Joseph Caproni who retained the name D.Brucciani and Co. The business continued to manufacture casts. As far as is known, the Ipswich Museum Tondo was made during this time.

According to the Catalogue of Casts, written in 1889, Brucciani was selling copies of the Tondo for £2 10s.

Conservation

The cast of the Tondo had been residing in a cellar for many years, where it sustained damage to the lower portions as well as suffering from damp.

The Tondo was first removed from its old frame. The cast was attached using large iron screws, all of which were corroded. Three screws were left holding the Tondo together.

Once in the lab the damage was assessed and a conservation plan made. The Tondo needed to be cleaned, repaired and mounted when complete. Through the whole process photographs were taken to document our work.

The Tondo was in desperate need of cleaning. This was carried out using a vacuum cleaner, melamine sponges, distilled water and conservation grade detergent. Extra care was taken to ensure the plaster did not become over wet. The water and dirt were dabbed off with tissue.

Once clean, the question was how to fix the Tondo back together? Being so large and heavy, normal adhesive would have failed. It was decided to adhere and fill the object from the rear using a foaming resin, which would hold all the pieces together, leaving the front free to fill with plaster where needed. A foaming epoxy was used, as it was lightweight and reversible in IMS/acetone.

The Tondo was laid face up and leveled. To work from the rear a plaster negative was made of the surface to hold the pieces in place when the cast was inverted. The object was covered in cling film and walls built to hold the plaster.

The plaster was left to dry for 3 days. Once dry, the Tondo was turned over to expose the rear.

Tensioning straps were used to pull the two broken parts as close together as possible. The join between the two main pieces needed to be as close as possible to prevent cumulative error. Any gaps leading to the front were filled with plasticine to prevent resin leaking.

Using fibre glass wading and resin, without blowing agent, a very strong bond between the two major parts of the Tondo was created. Experiments with the resin and blowing agent were also made to see how far the resin foamed. This was then leftover night to cure.

Once dried the tensioning straps were removed. 

The Tondo was to be displayed in the Wolsey Art Gallery on a board. It was decided to attach the cast to the board with bolts. Devising a level platform using angled aluminium, the bolts were leveled up for depth and spacing. Walls of dental wax and plasticine were made around each area to prevent resin spillage. Steel mesh was added to the back of the Tondo to give more strength and weighed down to ensure complete coverage with resin.

The resin was mixed in small batches and the blowing agent added. The process was exothermic and, once cured, the stabilising aluminium angle strip was removed and the cast turned over to review how the pieces had adhered.

The next challenge was to replace the missing section of the Tondo. The conservation team borrowed another copy from the Royal Academy, this being more refined with better detailing. A drawing of the missing area was made using Melinex. This was used to define the area that needed to be cast. The area of the loaned cast to be moulded was coated in a release agent. The moulding material was alginate, a water-soluble material. As the alginate was flexible, the mould was covered from behind with polyurethane foam to stiffen it, and to prevent it distorting during casting. Once cured we were able to pour plaster into the mould.

Using scalpels, drills, rasps and grinders, the new cast was trimmed so it fitted snuggly into the missing area. The edges of the Tondo were sealed with a PVA/ Water solution before the new cast was adhered using a thick layer of plaster.

This plaster was enough to hold the new and old pieces whilst the object was turned over in order to continue filling the back with resin. Using the same methods as before, a further three bolts were inserted and covered with foaming epoxy resin to the same level.

Once secured the bolts were trimmed, so 4cms showed above the resin. The resin could then be sanded down to create a level flat surface for the back board to sit.

Whilst the Tondo was upside down the edges were cleaned using acetone and IMS, which dissolved the excess resin, and a scalpel. The cast was then turned face up to inspect the front and the excess plaster between the old and new areas rubbed down or filled as necessary.

With curatorial support it was decided that the final piece would be painted to create visual harmony with the current exhibition. The original surface was also stained and ingrained with dirt that could not be removed. Chalk paint was chosen, as it was similar in composition to plaster and reversible in water.

A lightweight aluminium honeycomb board was chosen to attach the Tondo to. The aluminium honeycomb board was lightweight but very strong. The positions of the bolts were marked on a Melinex template, which was fixed onto the pre-cut board, and holes drilled.

The board was painted Hague Blue, like the gallery walls and the cast finally bolted to the board for the final time. The front of the painted Tondo received a coat of microcrystalline wax to protect it. This wax also gave the paint a slightly yellow hue, toning down the colour. The cast was then wrapped and transported from Ipswich museum to the Kiss and Tell exhibition in Christchurch Mansion.