The larger than average, 2.8m from end to tip, mineralised tusk of a male mammoth on display at the Willis Museum Archaeology Gallery under went a lengthy conservation process in 2014.
The mammoth tusk was found at Lodge Farm, North Warnborough, in 1973, and had previously formed part of the old Willis Archaeology Gallery display. Historic restoration work – well intentioned, but carried out with non-sympathetic materials - had begun to age and fail, causing damage to the remaining original tusk material.
In order to reconserve the tusk, the damaging old fills and surface coating had to be removed. They had been inflexible, and also stronger than the tusk itself. As the tusk had flexed with changes in humidity and temperature, the fills and surface coating had not. This had caused lifting of the surface, and pulling away of small fragments from the edges of the cracks – which were now much larger than before.
Removal of the fills and old coating was carried out using mostly mechanical methods, with some solvent to remove stubborn residues. It was decided to also remove the old painted plaster fill at the tip of the tusk, which actually covered up several inches of original tusk, and had been an aesthetic addition rather than a structural necessity.
The cracks in some cases were very deep, and full of dirt, dust, old fill and loose fragments of ivory which had split away. The fragments were removed so that no loose material remained to affect the application of new fills. Where the original positions of fragments were known, they were bonded back in place with reversible, conservation grade adhesive.
Once clean, it could be seen that the tusk was structurally quite fragile. However, the condition of the remaining patinated surface – though bare in places – was reasonable, and the true colour and texture had been revealed beneath the thick, yellowing coating.
The fills needed to be replaced, but this time with a sympathetic material that would be flexible, yet supportive, and not stronger than the mineralised ivory. Fills also needed to be conservation grade, easy to apply and remove, and – particularly given the size of the object - cost efficient!
Various tests showed that the most appropriate fill was a sort of conservation-grade papier-mache, using acid free tissue paper and a very flexible, low tack adhesive. Using paper as the bulk of the fill meant costs could be kept down, and the advantage of the papier-mache meant it could be packed down in the voids easily, providing complete support within the tusk.
Space was left for a thin skim of the same flexible adhesive, mixed with a bulking agent of glass micro-spheres and acrylic paint, to be added. Though these fills are obvious on close inspection, they should not now draw attention away from the object itself.