Conservation of Previous Repairs on Archaeological Ceramics

By Emily Thomas

The Project

As ceramics conservation students on the graduate diploma programme, we were asked to survey a section of the Novium Museum's ceramic collection in storage at the Fishbourne Roman Palace Collections Discovery Centre near Chichester. This is part of an on-going project to document and repackage excavated burials from St Pancras Roman cemetery. Assessment included checking the accuracy of the current documentation, condition assessment of objects and suitability of storage conditions.

The Common Problems

Common problems found in archaeological ceramic collections, such as the Novium's, are due to failing old repairs. Deteriorating fills and weakening/yellowing adhesive can be unsightly and potentially cause more damage to the original material. With so many examples of this kind it was essential to prioritise those objects most in need of conservation. Considerations include:

  • Stability of original object
  • Stability of repairs
  • Storage, eg. is it safer to store separate sherds or one bonded object?
  • Uniqueness of object, eg. will this object be used for public display?

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The Post-Medieval Green Glaze Dish

During the object condition assessments, we came across an unusual, but not unprecedented problem. A post-medieval green glaze dish had been brought to our attention by the Museum's curator. This dish had undergone previous conservation work. Sherds had been bonded and missing areas reconstructed with plaster, which was retouched with acrylics. The overall size of the dish was accurately determined by the profile and diameter. The repair was successful, firstly because it gave the previously disparate sherds a shape, making the object more easily readable, and secondly, the retouching of the fill was done in a sensitive tonal colour, which does not distract from the overall aesthetic but is easily readable as new material.

After the reconstruction, however, another piece of the dish was found. The dilemma now is whether to insert the piece into the fill or to leave it separate. Several things need to be considered including:

  • Potential damage to the object
  • Overall look of the object
  • Safety of the object in storage.

If the sherd were to be inserted into the fill, it could be done in a number of ways.

The Options

Firstly, we might consider excavating an area of plaster in which to bond the section. This method would be complicated as it would involve a lot of mechanical work, which may be difficult to do seamlessly. If the fill is damaged, it may detract from the overall aesthetic of the dish.

Secondly, dismantling the dish, removing the fill and adhesive may cause some of that adhesive and plaster to become trapped in the original body. Both of these options would be very time-consuming and potentially costly.

Both options would require consideration about placement of the sherd, as there is not one area in which it could be incorporated. A certain amount of artistic licence has already been executed with the placement of the other sherds, see figure 1. The positives in both cases, however, are that more of the original material would be incorporated into a whole and it would be less likely that original material would become lost.

Fig.1. (Top left) dish without newly found sherd, (top right) dish with sherd to the left of the fill, (bottom left) dish with sherd in the middle of the fill, (bottom right) dish with sherd to the right of the fill

The third option would be to leave the dish as it is, in its own box, wrapped in acid-free tissue paper, see figure 2.

Fig.2. Green glaze dish in storage.

The sherd sits on top of the dish, taking up no more room in storage than if it were all bonded. More pieces of the dish might be in the collection somewhere and we could not guarantee that, if further conservation treatment was carried out, the same dilemma would not arise in another few years' time.

Whatever the treatment decision here, this case highlights the need for reversible or at least re-treatable conservation work to be carried out on all objects so that we may deliver the best long term care of objects.

Fig.3. Emily Thomas at her workshop bench.