Church Bell Clapper
University of Lincoln
Condition
The clapper of the Stickford church bell is a composite object constructed of wrought iron mounted to uncoated ash wood secured by iron straps and bolts.
The wood suffered extensive damage from insect infestation including an area of loss. It split along the grain beneath the metal straps as a result of the different thermal and moisture expansion rates of the wood and metal. Tannin staining of the wood occurred around the iron straps. The iron surfaces were all actively corroding with light pitting and akaganéite present in some areas.
Treatment Aim
To preserve and protect the materials of the clapper while restoring the visual understanding of the object for public display in an uncontrolled environment at St Helen’s Church, Stickford.
Treatment
Insect treatment
The clapper was wrapped in plastic and placed in freezer at -30°C for five days to kill all stages of infestation.
Wood Consolidation
Cyclododecane was applied as a barrier layer to the wooden surface to prevent discolouration during consolidation. Cocktail sticks were used to keep the flight holes open for consolidation injection. The wood was pre-wetted with acetone to prevent reverse migration before two injection treatments of 10% Paraloid® B72 in acetone/ethanol (50/50) and two injection treatments at 15%. Between treatments the cyclododecane surface was swabbed with acetone to remove excess consolidant, then wrapped in plastic film to slow its sublimation and the evaporation of the solvents. Once the consolidation treatment was complete, the cyclododecane was wicked from the wood surface using a heated spatula and tissue to speed up the sublimation time. After a week, the remaining cyclododecane was thin enough to be brushed from the surface using a stiff fibre brush.
Metal Treatment
Corrosion was mechanically removed using steel, brass and glass bristle brushes. The corrosion dust was removed using a white vinyl eraser before sealing with paraffin wax. Paraffin wax was chosen for this treatment as it performed better than microcrystalline wax in a high RH environment during testing. Efficiency of the moisture barrier was considered to exceed the reversibility of treatment when returning this item to an uncontrolled environment where RH above the recommended level of 40% for metals is extremely likely.
Gap Filling
The timber splits were filled with a flexible fill of Arbocell® BC100 in solution of 7% Klucel G in IDA / distilled water (90/10) to allow for continual movement of the timber when displayed in an uncontrolled environment.
A detachable fill was constructed from shaped balsawood for the area of wood loss. It was cut in strips, built up incrementally and fixed together using Paraloid® B72. Irregular recesses unable to take the balsawood fill were initially filled out with the Arbocell® BC100 and Klucel® G mixture to create a level surface.
