Archaeological pottery
Object property of UCL Archaeology Collections
Object before treatment
Object after treatment
Condition before treatment
Past conservation treatment has failed and the object comes in a fragmented state, the slip layer is loose.
Treatment
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Removal of past adhesives:
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The smaller joints were taken down using with cotton wool strips which were fed with acetone using a pipette. Aluminium foil was placed on both surfaces (interior and exterior) to delay the solvent evaporation. The joints came down easily as adhesive was very brittle, but the bigger joints needed to be put in a solvent atmosphere.
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The object was padded with acid free tissue paper and the joints were secured with clamps and padded wooden skewers placed to counter any potential movement once the adhesive has softened.
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Consolidation: A 10% solution of Paraloid B72 in acetone with added fumed silica was selected as an appropriate consolidant for the vessel. This was applied with a soft brush in uniform sections across the surface. In areas where there was significant slip loss, the surface was first saturated with ethanol applied with a pipette to avoid the formation of tidemarks by slowing down the evaporation of the acetone.
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The bowl was reconstructed using 50% w/v Paraloid B72 in acetone.
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Two small fills were done for structural support of some weak joints which were in-painted with watercolours.
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The bowl was placed on a tray of Correx, padded with 30mm plastazote sheet. A base for the bowl to be placed upon was created with two ethafoam rings which are held in place with wooden skewers and secured with cotton tape. The surface of the mount is lined with a sheet of Tyvek fabric to prevent any abrasion between the slip and the ethafoam rings.
Justifications
Removal of past adhesives: This was done with a combination of methods as due to the size of the object and its friability, it was difficult to place all the fragments in a single container to create a solvent atmosphere.
Cleaning: The surface of the object was not cleaned as this would cause further damage to the delaminating slip.
Consolidation: Other materials tested:
8% Mowital B30H in ethanol - this was good but did not provide sufficient tack to keep the flaking slip into place
5% Paraloid B72 in xylene was penetrating deep into the ceramic fabric, so not enough tack was created on the surface where it was needed for the slip flakes to be stabilised.
10% Paraloid b72 in acetone with added fumed silica; this was selected because of the fast evaporation of the solvent the adhesive remained on the surface and provided enough support for the flaking slip
The surface is now saturated and there is some darkening as expected after a consolidation treatment - this was necessary as there was continuous loss of the slip layer
