April 1993 Issue 07
Mind the gap: conservation of a Delftware bowl
In 1965 several pieces of early English delftware were donated to the Victoria & Albert Museum by a Professor F.H. Garner. Professor Garner had collected the objects during the Second World War, when he lived for a time in London. According to legend he had rushed to the old kiln sites around Lambeth as the bombs were dropping and collected any shards revealed by the disturbed earth! Using extremely rudimentary conservation skills he attempted to assemble the fragments with a paste of animal glue and sawdust and it was in this form that they came to the V&A.
The problems connected with the conservation and restoration of these delftware fragments then fell to the members of the Ceramics Conservation Studio. They were asked by Michael Archer, of the V&A Research Department, to conserve the pieces in preparation for photography for a catalogue on English delftware. By examining the shapes and designs of some of the pieces, Michael Archer had ascertained that they were important early pieces and, as such, merited the extensive conservation that they required. This article outlines the conservation treatment of one of these delftware pieces. Michael Archer believes the bowl to be a sugar bowl, which would possibly have had a cover, based on comparisons with objects in paintings of the same date.
The bowl fragment (Fig. 1), was originally found in 21 pieces. Nineteen of the fragments fit together and two are 'floating' pieces, that is they do not connect to any of the other fragments. About two thirds of the bowl is missing. The previous restoration by Professor Garner was quite crude and this restoration has been reversed. The fragments were cleaned and the 19 fragments that fitted together were bonded (FIg. 2)
The next stage of the treatment was to find some way of making up the missing area, in order that the bowl could be viewed as whole object, rather than fragments. This was concidered necessary not only for the obvious aesthetic reasons, but also because some method of combining the fragments into one object would make them more stable from a conservation point of view, less prone to further damage and easier to handle. In addition, combining the fragments now avoids the possibility of them inadvertently becoming separated later. Several approaches to the reconstruction were concidered.
One method would have been to use dental wax to take impressions of the existing interior and exterior surface. These impressions could then have been used as moulds to build up the missing area. However this would have been very time-consuming and would probably have resulted in an imperfect fill demanding much finishing. In view of extent of the missing area this method was not really appropriate.
In the past, notably in archeaological conservation, a method of reconstruction using a core upon which the fragments are placed and the gaps are filled with plaster has been successfully employed. This involves making a profile of the object, both inside and out. A core is then foprmed to match the inside profile of the object. This core is usually made of a soft substance which can be easilily removed later and in the past plasticine or clay wrapped around cardboard has been used.
Once the core has been formed as accurately as possible, the fragments of the original object are placed on it and the gaps are filled with plaster. Using the exterior template, the plaster, while still wet, is pared down until it is flush with the fragments. When the plaster is dry the core can be removed. The problem with this method is the way the fragments are used in the construction of the plaster fills, which may put them at risk. A variation on this method is to construct a core and cover it in plaster, then while the plaster is still wet, turn the plaster shell against an exterior profile template until a plaster replica of the object is created. The plaster shell can then be cut to 'let in' the fragments of the original object This method can sometimes result in an imperfect replica which requires much sanding down.
The final process which was considered was one suggested by a ceramics tutor at the Royal College of Art, Mr Tony Sims. This method had been used for a long time in the ceramics industry as a method of making presentation and production models and the advantages were speed, quality of finish and the fact that most of the work could be achieved without involving the precious fragments. It was this technique that was adopted for the reconstruction of the delftware bowl, as outlined in the next column:
Measurements were taken of the reconstructed fragment to determine the exact diameter, height and thickness of the beaker
A zinc template was marked up with all the profile information, inside and outside and then cut to the inside profile (Fig. 3)
Plaster was poured into a cup head, or chuck, which was cottled around with plastic. When the plaster was on the point of setting, the cup head was fixed onto a lathe and the plastic was removed, leaving a cylinder of almost set plaster attached to the lathe
The plaster was turned, using the zinc profile, until it resembled the inside profile of the beaker(Fig. 4)
The zinc template was then recut to match the outside profile of the beaker
The cup head, with the now solid core, was removed from the lathe and the core was sized with soft soap, -which would act as a release agent
The core was then cottled around with plastic again and plaster was poured over the core to cover it completely
When the plaster had almost set the cup head was again placed on the lathe and the plastic was removed
This time, using the recut zinc template, the plaster was turned to the outside profile.
When the plaster had thoroughly set the outside shell was removed from the core. This was easy as the core had been well sized with soap (Fig. 5)
Finally the foot ring and the rim of the beaker were trimmed after centring the shell onto a whirler and securing it down with clay (Fig. 6)
The whole process was carried out by Tony Sims at the Royal College of Art and took about five hours. During this time it was possible to produce two plaster shells. The next part of the process was to cut the part of the beaker that existed away from the- plaster replica and fit the original fragments in place. A sheet of dental wax was heated and applied to the inside and outside of the fragment piece. The wax was then carefully trimmed to the edge of the ceramic, removed, then placed on the plaster shell. An outline of the fragment shapes could be drawn on to the plaster shell in this way. It was then possible to cut away these pieces with a dental drill. This was quite a tricky process and it was nice to know that there was a spare plaster shell should the first one break! It was also possible to fit in the two 'floating' fragments by looking at the pattern on the fragments of the original bowl and calculating where the two pieces would have fitted in (Fig. 7).
Fig. 7. Cutting the plaster shell to allow for the 'floating' fragments to be fitted (click image for larger version)
Once the plaster shell had been cut, a base colour was applied to it using an air brush. The shell was sprayed a base colour of bluey - grey with dry artists pigments and an urea formaldehyde retouching medium - Rustins Plastic Coating. The large fragment piece and two small floating ones were attached to the tinted plaster shell with Paraloid B72. Any gaps were then filled with tinted Polyfilla, which was also retouched with dry artists pigments and Rustins Plastic coating (Fig. 8).
Using the expertise of a skilled potter at the RCA meant that the production of the plaster shell was relatively quick and precise. Following on from this initial trial Tony Sims has now made plaster replicas of two more delftware pieces.
There are some drawbacks with this method, notably a problem with using the perfectly circular shells produced on the lathe with the fragment pieces from objects which are not perfectly centred. For that reason this process is best suited to fragments which come from perfectly centred objects or where the majority of the object is missing and only a few fragments need to be fitted in. In addition, no way of dealing with objects with undercuts has yet been developed. Nonetheless, this alliance of modern production methods and old ceramic fragments has proved successful and rewarding and it is hoped that the process will be developed further.