Head of Commodus
Object property of The British Museum
Head of Commodus before treatment
Photo property of The British Museum
Head of Commodus after treatment
Photo property of The British Museum
Condition before treatment
The head was loosely secured on a dowel and base as the previous fill material had failed. There was a discoloured previous restoration on the nose area and residues of cleaning material applied in the past in the curls of the hair and the beard. There were various abrasion marks on the neck area and chipped edges on the base. Furthermore, the head rested too close to its base, not allowing for full appreciation of its sculptural quality.
Treatment
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The surface was dry cleaned with brush and vacuum
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The surface was wet cleaned with saliva and deionised water
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The old, discoloured pigments on the nose were removed with swabs of acetone on cotton wool
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The head was removed from the base and the supporting dowel by using acetone on the exterior microballoon fill and by softening the interior plaster with deionised water.
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The crack between the nose and the face was filled in with Flugger (acrylic putty)
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The nose was toned-in using Winsor and Newton acrylic pigments to match the surrounding fabric.
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The square dowel hole in the head was lined with aluminium hydroxide in 20% Paraloid B72 (ethyl methacrylate copolymer): Paraloid B48N (methyl methacrylate/butyl acrylate copolymer) 2:1 in a 1:1 solution of IMS (Industrial methylated spirits (ethanol, methanol) and Acetone, (propan-1-one/dimethyl ketone). The internal surface was given a curved square shape to allow for the subsequent resin fill to ‘lock in’ place.
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The base was drilled from its underside to allow for the use of a nut on the bottom which would secure a threaded dowel in place.
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A new dowel was made by inserting a smaller circumference threaded dowel in a thicker polished dowel and securing it with a pin. The top part of the dowel was scored to allow for futher securing the resin.
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An internal ‘lip’ was created approximately in the middle of the dowel hole on the base. This allows for a removable base so the head can be used for on-shelf display. There are wooden wedges in the interior of the base to secure in its vertical orientation. The gap around the dowel on the base, was filled with aluminium hydroxide filler in 20% Paraloid B72 (ethyl methacrylate copolymer): Paraloid B48N (methyl methacrylate/butyl acrylate copolymer) 2:1 in a 1:1 solution of IMS (Industrial methylated spirits (ethanol, methanol) and Acetone, (propan-1-one/dimethyl ketone).
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The new dowel was secured in the head using Steinkitt (polyester resin). A layer of microballons (silica or phenolic resin) in 20% Paraloid B72 (ethyl methacrylate copolymer) 1 in a 1:1 solution of IMS (Industrial methylated spirits (ethanol, methanol) and Acetone, (propan-1-one/dimethyl ketone) was used as a final fill material to produce the desired finish.
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The fills were toned-in with Winsor and Newton acrylic pigments.
Condition after treatment
The surfaces are clean of any old conservation materials and any unstable areas secure.
The head is now secured on its dowel and base and safe to travel and be exhibited. The removable dowel solution allows for its exhibition either on its current base, or it can be mounted on a shelf or plinth.
An effort to make the polyester resin reversible was made by using aluminium hydroxide filler as a barrier layer between the stone and the resin, so the dowel can be removed if necessary without having to use toxic chemicals.
