NPL Investigates Effectiveness of Wax Coatings at Protecting Westminster Abbey's Stone Floors

The National Physical Laboratory (NPL) has taken part in a City & Guilds of London Art School project to investigate the effectiveness of wax coatings at protecting the stone floors of Westminster Abbey.

With the number of visitors to historic sites increasing year on year, conservation efforts are crucial to preserving and enhancing the UK's cultural heritage. Ledger stones, which mark places of burial and cover the floors of many cathedrals and churches, are particularly vulnerable to damage from high footfall, with inscriptions and decorative carvings disappearing underfoot.

Current policy at Westminster Abbey is to not reinscribe ledger stones, making their effective protection essential. This can be attempted in various ways: floors can be protected by barriers or covered with mats; stones can be repositioned in less busy areas, or removed completely and placed in a museum.

Alternatively, protective coatings can be applied. Conservation Studies student Rebecca Davison undertook a project to assess ten wax formulations for use as protective coatings on polished limestone floors, such as those found in Westminster Abbey and many other historic buildings.

Waxes were applied to Tournai 'marble' (actually a black limestone) samples provided by Westminster Abbey at City & Guilds, and a micro-tribometer was then used at NPL to simulate the abrasion caused by dirt and grit brought in on visitors' shoes.

Ten microcrystalline wax formulations were tested for their abrasion resistance, formulated with varying amounts of polyethylene additives and dispersed in different hydrocarbon solvents. Abrasivity was measured by means of 3D confocal microscopy. Experiments were also carried out in Westminster Abbey itself, where the waxes were applied to a typical ledger stone and assessed for longevity eight days later.

None of the ten wax mixtures tested was found to offer protection against abrasion or promote longevity under heavy footfall, but the results confirmed that the addition of polyethylene wax lessened the tendency of visitors to slip on the surface. The research recommends that regular vacuuming, as well as the use of mats at all entrances - especially from the Cloisters, where there is severe weathering of Yorkstone flags - achieves better protection of historic floors than the wax coatings tested.

Source: http://www.npl.co.uk/

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