Mats for medieval tiled pavement

Last year, English Heritage cleaned the medieval floor tiles in the
Chapter House at Westminster Abbey, London.  In order to protect the
tiles from grit and dust we are proposing to install dust-arresting
matting on the steps leading up to the Chapter House, and as a
walkway round the perimeter of the Chapter House.

According to the manufacturer, the backing of the matting is an
acrylonitrile butadiene rubber with a carbon black filler.  It is
plasticised with a phthalate ester, and other components include
antioxidants, process aids, activators and sulfur-based vulcanising
agents.

We are concerned that there should be no chance of the migration of
any deleterious substances from the backing, either as primary
materials or as products of alteration.  Has anybody had any bad
experiences in the use nitrile-backed mats on historic floor
surfaces, particularly tile or stone?

Dr Barry Knight English Heritage London

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                  Conservation DistList Instance 12:26
                Distributed: Tuesday, September 15, 1998
                       Message Id: cdl-12-26-012
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