Above, Victorian statues in medieval niches on the lavish West Front at Beverley. The Minster escaped the worst excesses of Reformation and Civil War. Below, the building seen from the south, its traditional setting largely intact
put sulphates and other salts derived from pollution into suspension,which would then re-crystalise at or near the surface of the stone as evaporation and drying progressed. This could lead to efflorescence or, in extreme cases, loss of surface material, forced off by expansion of the crystals as they formed. It is doubtful thatwewould use the same technique now. We did use an alternative technique on delicate internal sculpture, whichwas based on poultices of
attapulgite clay, applied wet and keptmoist for some time. This softened and loosened the surface dirt and, as slowdrying out was allowed under controlled conditions, salts and pollutants were drawn out into the clay, which was then removed and the stone rinsed. Clearly this is a laborious process that produces large volumes of waste product, which could never be suitable for large areas of plain surfaces. Recently a newcleaning technique has become
available,which has been used to startling visual effect on the interior of St Paul’s Cathedral, Kelvingrove Art Gallery andMuseum in Glasgow and a small area in Ripon Cathedral, apparently without detriment. It is
based on natural rubber latex with a complex chemical entrained, ethylene diamine tetra acetic acid, known by its acronym, EDTA. This material can be brush- or spray-applied in a very controllable manner. The active chemical “digests” the dirt but, as the latex sets in a fewhours, becomes entrapped and ceases itswork. The latex is then peeled off, completewith dirt. Persistent soiling can be re-treated. Sponging down with clean water is usually necessary to remove any residues. This seems to be a very promising technique for interiors, which uses very little water, no abrasives and is silent in application. Sadly it does not seemto work externally, and our limited trials inside the Minster have not been hugely successful.
ALL the roofs of this great building are covered in lead, as they almost certainly always have been. This is an expensive material both to buy and lay, but, if properly laid, its long life makes it more economical than other materials in the longer term. It also looks stunning. Formore than a decadewe had a rolling programme of roof repairs, and much of the lead wewere dealingwith was last re-laid in the 1820s, so it did not owe usmuch. Virtually all the lower level roofs of theAisles and the Vestries have been relaid, as well as the Central Tower roof and the West slope of the NorthQuire Transept. The technique employed has been to strip the old lead, take it away to the workshop, melt it down, augment the volume as necessary, re-cast it as newsheets on a sand bed on a casting table and refix it on the repaired carpentry of the roofs. Few firms still carry out this highly skilled casting process. Most newlead these days is milled–that is, rolled out cold like pastry.We have used all the available firms over the years,Norman & Underwood of Leicester, Anglia Lead ofNorwich, CEL of Peterborough, who have taken overAnglia Lead after the sad death of their admirable Bob Bangay, and
Cornerstone, Vol 32, No 2 2011 51
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