Summer 2001 Issue 38
A Chinese Figure in Unfired Clay: Technical Investigation and Conservation Treatment
A rare Chinese portrait figure was recently acquired by the Far Eastern Department of the Victoria and Albert Museum (V&A No. FE 24-1999) (Fig. 1). It depicts a man lounging on a wooden bench and dates from around 1740. The figure is made from unfired clay over an armature and is painted.
In 1952, whilst privately owned, it was named 'The Model of an Unknown Man', and mistakenly attributed to the Chinese modeller Chitqua who worked in London from 1769 to 1772. Other than Chitqua's work, who was active outside China, portrait statuettes of Europeans were solely manufactured in Canton, from 1700 to c.1800.
These depicted western merchants and officers as perceived by oriental viewers. Due to the nature of unfired clay, few examples of such figures survive. They bear similarities to the V&A figure, suggesting the same provenance. In particular, their size is small (heights range from 10 to 30 cm according to posture), the clay is grey-white, unfired and supported by a bamboo or wooden armature. The heads of some are detachable, implying a possible practice of adjusting the portrait to a ready-made body.
The figure was in a poor state of preservation. The proper right hand, the left foot, fragments from the neck and the cravatte, and half of the book were detached, whilst the other half of the book was missing. The head, the right foot and the lower part of the garment were loosely held, exposing the deteriorated clay. Surprisingly, the clay failed to provide a durable substrate, leaving the paint layer unsupported in those areas only. The bamboo armature was visible in the broken area of the neck. The prominent right hand had been modelled on a bronze armature that was oxidised, and had been attached to the body with a rusting iron dowel.
The statuette bears old interventions and restorations. The proper left hand had been adhered with a darkened brown resin, possibly shellac, which had shrunk and distorted the clay substrate. Transparent resin residues are present at the backside of the neck and in the hand. Various materials have been used for filling, especially in the lower part of the garment and in the shoes where only a small area of the original material survives. Moreover, overpaints were found on most of the surface, and in the case of the cushion, a fine red decoration had been completely hidden.
The wooden bench is well preserved and bears a few symmetrical holes, possibly from nails holding a fabric. Chinese inscriptions on the legs indicating their position, verify that it had been constructed in China, to accompany the figure.
The technical investigation of different aspects of the figure provided further, useful information on the manufacturing technique of such objects.
Microscopic observation revealed the physical condition and the stratigraphy of the figure. The exposed clay was in a very poor state and fibres were present in the ground layer of the polychromy indicating the presence of fabric or paper. However, the clay in the rest of the statuette seems to have survived in a good condition.
Pigment samples and cross sections of the polychromy were examined by Sasa Kosinova under polarised-light microscopy. Overall, chalk and gypsum are present as ground layers, azurite of high quality is the original blue, whilst original red is vermilion. Dark blue overpaint is Prussian blue and there are also 20th C. blue and red present, most likely as part of past restorations.
The figure was also examined under infra-red radiation, in order to distinguish possible fibrous materials in the ground with negative results. Under raking visible light, cracks became apparent on the skull of the figure. The object was also x-rayed, and the armature and older fills were fully exposed to view (Figure 2).
Finally, it was examined under ultra-violet radiation. Later fills in the garment fluoresced, whilst the unfired clay did not. The technique was also intended to trace any further lettering on the book, but no writing other than the existing was visible.
To sum up, the figure was manufactured as follows: White clay was modelled around a bamboo armature, while for the prominent hand, the more flexible bronze was used as support. In the lower part of the garment, a fibrous material covered the clay, most probably for modelling the drapes. The head may have been executed separately and attached to the body with bamboo sticks. A yellow ground layer was applied to the surface, followed by a finer white layer on which polychromy was executed in the final stage.
Due to the fragile materials of the statuette, we had to take into consideration diverse factors. Firstly, unfired clay is a material susceptible to humidity and some areas had already irreversibly deteriorated. Secondly, the structure needed strengthening in various places and the original paint layer was flaking and required immediate consolidation, while overpaints affected the appearance of the figure and the preservation state of the original polychromy. Finally, different types of fills were required, according to aesthetic or structural purposes.
Initially, heavy dust was removed by soft brushes. Solubility and consolidation tests were carried out in order to determine the effect of solvents on the polychromy. Azurite and Prussian blue were found to be affected by water, acetone, IMS and isopropanol. 1-methoxypropan-2-ol did not have an effect on them, whilst white spirit slightly dissolved Prussian blue, but did not dissolve azurite. The white overpaint on the cushion was dissolved by ethanol and water, the latter however did not affect the original white layer. The red paint layer was dissolved by IMS but remained unaffected by white spirit and water.
Solvent cleaning was applied selectively in areas of accumulated dirt. The head was cleaned with white spirit, the hand was cleaned with a poultice of ethanol and water and the overpaint on the cushion was removed mechanically and with the aid of water. The remaining overpaints were not removed because the preservation of the original materials could not be guaranteed.
The aim of the consolidation treatment was to secure the unfired clay and the paint layer while avoiding any optical change of the surface. Consolidation tests were performed in areas of loss by using different solutions of Paraloid B72 and Aquazol 500. Since the use of purely water-based treatment was excluded as too risky for the unfired clay, those two acrylic resins were chosen because they polymerise by solvent evaporation. Moreover, Paraloid B72 is dissolved in a wide range of solvents, is readily available, displays long-term stability and is widely used with satisfactory results.
On the other hand, Aquazol™ [poly(2-ethyl-2-oxazoline)] is a material that had not been used by our studio before and we wished to assess its suitability for use on sculptural material. More specifically, it can be dissolved in a range of solvents, is stable, does not cross-link during ageing, it depolymerises though, and is recommended bibliographically for the conservation of complex painted surfaces. Additionally, it does not cause discolouration which contributes, in theory, towards its advantages.
Various concentrations of solutions of Paraloid B-72 and Aquazol 500 in IMS were tested. It was decided to use a solution of Aquazol 500, 4% in mixture of water/IMS 1:2. Although this introduced small amounts of water, it was considered acceptable and suitable for the consolidation of both the unfired clay and the polychromy as it provided enough strength without causing darkening or swelling.
Moreover, water permitted softening and flattening of the preparation layer while IMS in the solvent mixture increased permeability and accelerated evaporation. The lifted flakes were indeed successfully flattened and where necessary, Aquazol 500 solution, 5% in IMS only, was afterwards applied for faster and firmer adhesion to the substrate. The loose and detached pieces of the neck were adhered with thick solution of Aquazol 500 in IMS (20%).
Old fills in the boots and the lower part of the garment, were removed, unveiling the unfired clay in a very bad state of preservation. Distorted areas were softened with Aquazol 500, 4% in mixture of water/IMS 1:2, and where required, paint flakes were supported with Japanese paper in order to preserve original polychromy onto the new fill. Fills of structural strength were required in the area of the neck and the right hand, and were executed with whiting mixed with Aquazol 10% in water. Restoration fills of the garment, the boots, the book and the fingers, where strength was not necessary, were made with whiting mixed with isinglass.
Retouching the fills was performed with pigments and Aquazol 500, 10% in water, as medium. The areas of the figure where the polychromy was missing but the substrate still existed were not colour matched but left. This was due to the complexity of the original materials, in case of a future retreatment, and for displaying the manufacturing technique.
The silk hat that is recorded to be worn by the figure and survives in pictures in the archives of the National Portrait Gallery, is to be reconstructed by the Textiles Conservation Studio in order to restore its original appearance.
The rarity of such figures renders preliminary examinations and ethical decisions very important. Moreover, the introduction of Aquazol 500 in various stages of the treatment had very satisfactory results, in accordance with the conservation bibliography. In particular, Aquazol 500 served as a consolidant, filling and retouching medium, thus it enabled us to achieve the desired results while only introducing a single material into the object.
I would like to thank Verity Wilson, Charlotte Hubbard and Nigel Bamforth for their advice, and the staff of the National Portrait Gallery Library and the Royal College of Physicians for allowing access to their archives.