Conservation of a memorial silver plaque

Hugh Alexander MacPherson (1858-1901) was an important figure in the history of Carlisle, as he was a noted naturalist who spent many years as a curator of what is now called Tullie House Museum, working to increase the range and significance of the collections. After his death in 1901 this silver memorial plaque, showing his portrait in profile surrounded by plants and animals and mounted on an oak supporting frame, was commissioned from Ramsden & Carr, a firm of silversmiths whose work is now greatly sought after. While there were some signs of previous cleaning and restoration work (including the provision of additional fixings to hold the silver to the frame) the plaque appeared to be stable, but was no longer considered displayable due to its appearance.

The silver had become tarnished and unsightly, but it was not possible to clean it effectively without damaging the oak frame. After consultation with the curators at the museum it was decided to dismantle the plaque by removing the silver nails that hold it to the oak. The reverse of the plaque proved to be filled with plaster that once supported the thin silver but which had become fragmented and ineffective with the passage of time. The old plaster was removed and revealed that the central portrait was an electrotype, while the surrounding plants and animals were expertly modelled in repousse silver.

The plaque was cleaned by a variety of methods including solvent cleaning, electrolytic cleaning and traditional hand polishing with Goddard's silver pad polish in order to remove both tarnish and a tenacious organic coating that may have been based on linseed oil or a similar material. The cleaning was followed by a coat of acrylic lacquer to prevent direct handling of the silver surface and delay the formation of fresh tarnish while on display.

The oak frame had been waxed in the past, leaving it dull with unsightly streaky residues in the grain. These were removed with a stiff brush and the wood was revived with applications of traditional shellac-based furniture polish. The supporting plaster at the back of the silver plaque was replaced with more flexible but equally reliable silicon rubber, and the object was carefully reassembled, replacing each silver nail in its original position.

The plaque before treatment The back of the plaque showing damaged plaster support The back of the plaque showing the new silicon rubber support The plaque after treatment and reassembly