July 2013
Over the last few months, the Conservation Department has been preparing objects for Thetford Ancient House Museum’s exhibition ‘Lost Tudor Sculptures’. The stonework, a mixture of sculpted figures and architectural fragments, are from monuments planned by Thomas Howard, 3rd Duke of Norfolk. These tombs, which were meant for himself and Henry VIII’s illegitimate son, were never finished. The exhibition, which is the culmination of a large research project, aims to reunite fragments held by the British Museum, English Heritage and NMAS for the first time since they were excavated.
Above: Architectural fragments
Although the stonework was in a stable condition, it required significant surface cleaning as the fragments had accumulated a lot of ingrained dirt. The fragments are made from a soft chalky material often referred to as ‘clunch’ and are both porous and fragile. Careful consideration had to be given before deciding on a cleaning technique that wouldn’t cause any surface damage. An additional challenge was that some of the pieces were polychrome. Polychrome is a term used to describe the practice of decorating architectural elements, sculpture, etc., in a variety of colours. This was common practice in medieval Europe, where religious sculptures and interiors of church buildings were often brightly painted.
Above: The image on the left shows a figure that has lost all but tiny traces of polychrome whereas the image on the right clearly shows the once vivid reds that would have adorned the sculptures. Even the book the figure holds is decorated.
All the objects were first cleaned using a soft bristled brush and a museum vacuum cleaner. This is often the first cleaning treatment for objects, as it is gentle and fairly non invasive as the vacuums suction can be controlled. After testing a few cleaning methods, latex sponge was chosen for the non-polychrome objects. Even this soft squidgy material proved too abrasive for some of the objects and was certainly not suitable for those with polychrome surfaces. In order to ensure the painted surfaces were cleaned without disturbing the pigments, saliva was the final cleaning method chosen.
Left: A small cotton wool swab, which has been moistened with saliva, is used to gently lift dirt from the painted surface.
Although it may sound disgusting, and certainly not suitable for all objects, saliva has long been used as a conservation cleaning agent for all kinds of materials, especially gold leaf, and paint layers. Although it is generally agreed that it is the enzymes (particularly lipases and hydrolases) present in saliva that break down dirt and grease, the biological make up of saliva is complex and varies from individual to individual which makes its cleaning power difficult to evaluate. A great deal of research has been done in order to capture the cleaning properties of saliva and recipes for synthetic substitutes can be used.
The objects have been powerful teaching aids to explain the ethical considerations behind our treatment choices.
Above: Discussing conservation of polychrome material with a young visitor, Thetford Ancient House Museum, Archaeology day event 13th July.
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