Anti-stone cleaning myopia

relevance in the context of the Venice and Burra Charters. Nor can dirt have invested in it qualities of historical evidence, as some would have us believe. There is no virtue in filth, whether it be applied to the stonework, the paintwork, or the glazing of a building. The same ethical objections to the cleaning of stone are not — as a matter of course — applied to other elements of our historic past, such as paintings, sculptures, manuscripts or books; archaeological finds are cleaned prior to their conservation, study and

display.

One of the formal objections by Historic Scotland to the granting of consent for the cleaning of the Scott Monument was that “the visual effects of cleaning are unlikely to last”. The logical extension of such an argument would be for the AA or the RAC to promote the advice that car owners should not wash their vehicles because they will only get dirty again, or for Pilkington Glass to offer similar advice to purchasers of their products.

Dirt symbolises neglect, the unloved, the unwanted. It encourages the view that old buildings have a finite life and that their conservation is an anachronism. The unnecessary retention of dirt on old buildings is a passive form of vandalism that inspires the active.

Dirt hides decay; it conceals fractures, de-lamination, defects in detailing, old repairs undertaken using incompatible materials, the migration of iron (rust staining) caused by weathering or plumbing problems (which in turn may result in timber rot to structural elements behind). It is precisely because cleaning, correctly defined, removes dirt and shows up such items that it will not make an old building look new; but neither does it cause these defects, as is claimed. The cleaning of heavily soiled buildings is an essential pre-requisite to their proper repair and conservation, irrespective of whether the dirt itself is causing any damage.

Perversely, and this is another of the formal objections to the cleaning of the Scott Monument, there is a faction of the anti-cleaning lobby which objects to cleaning precisely because the end result would not be like a new building. Namely, cleaning would reveal a weathered building which showed variations and discolourations which are currently disguised. So the retention of dirt is justified in order to provide an even mantle to camouflage what is behind. Is this really what the authors of the Venice and Burra Charters had in mind?

Of course, undeveloped knowledge and skills and the over-enthusiastic application of certain cleaning methods have, in the past, damaged the stonework

of buildings. In Edinburgh, the abrasive method applied to Robert Adam’s Register House led to ioss of surface and detail; the chemical cleaning (presumably hydroflouric acid in too high a concentration) of the Palace of Holyroodhouse has introduced a dark brown colour which cannot be attributed to the original stone. These and other historical examples dating back over several decades should not be taken out of context and used to state or imply that the cleaning of sandstone is always damaging.

The cleaning industry has moved on, frequently in advance of the methods which have been officially supported in the past. Trials have taken place with poultice methods, though personally I am not convinced of the results. Trials have yet to take place using the range of highly controlled abrasives that are common elsewhere in Europe, and are favoured in France on limestone instead of our obsession with water (the excessive application of which can lead to non- reversible staining).

Prior to the 1992 Stone Cleaning Conference my practice successfully cleaned buildings in Edinburgh’s Royal Mile without the use of either abrasive or hydrofluoric acid treatments, the two methods which the anti-cleaning lobby had presumed were the only ones available for sandstone. I simply used, after wetting, a low-dwell-time degreaser (Neolith HDL) as effective cleaning agent followed by acetic acid substitute (Neolith 907) to neutralise it.

Recently (June 1993) I learned that the chemical consultant to the supplier of the chemicals used in that instance applied, but was not given the opportunity, to present a paper at that Conference.

Much has been said recently about algal colonisation. Algae have their origins in dampness, not geology, chemistry or other scientific specialisms. They may result from building or detailing defects, but are more likely to be climatic in origin. After a succession of mild, wet winters and cool, damp summers it is hardly surprising that algae can be seen in abundance on buildings in Glasgow, where they do not discriminate between dirty old, cleaned old and new stonework. They are green (not black) because of the Clean Air Acts: they are not an invention of the stone-cleaning industry. Indeed, one of the finest examples of algal colonisation in Edinburgh may be seen (if you visit it soon, before a cleaning contract removes it) on the angled stonework on the north face of the National Library building (phase I) in Causewayside: its construction was only completed in 1987.

In all of this one detects a determination to adopt all and every technical argument in an attempt to prove that stone cleaning is damaging, to ignore or deny current and historical sound practice, and to over-ride the whole technical debate with a philosophical argument which attempts to redefine the word clean to something other than its correct use within the English language.

There is also a complacency here about the public support for building conservation. Fashions come and go. Currently it is fashionable to denigrate stone cleaning. It is barely 20 years since we were still ripping the hearts out of many of our historic cities, in no small measure because it was fashionable to destroy soundly built housing stock solely for its lack of serviced amenities. It is only the current recession that has halted new waves of destruction in certain of our cities.

We must avoid playing Russian roulette with our heritage by undermining public confidence in our established environments. We cannot afford it economically, architecturally or socially. We must recognise that cleaning, properly defined, has contributed enormously to enhancing the perceived and real value of our historic buildings, thereby directly affecting the availability of the money to repair and maintain them. We can, and must, learn the technical lessons, and keep an open mind on the issues of principle.

The attempt which is currently being made in Scotland to deny the value of cleaning as a direct and essential contributor to practical conservation, and as an essential psychological partner to a conservation-orientated philosophy, is to fail to see the wood for the trees. It is a highly dangerous, intellectually purist, myopia.

One of many hopeful signs in this debate is that English Heritage — which, in the North of England, must be concerned with just as much sandstone building as is Historic Scotland across the border — does not share this myopia. Nor do conservationists in North America and Continental Europe. Indeed, the more feedback I receive from abroad the greater my realisation that the anticleaning lobby in Scotland is not so much a branch as the root and stock, operating to its own agenda. How long Historic Scotland can sustain its support for this lobby remains to be seen.

Dennis Rodwell presented a paper at the 1992 Conference on stone cleaning in urban conservation. He also made representation at the Scott Monument public local inquiry upon the environmental case in favour of its cleaning, and has spoken at a number of events organised by the construction industry to debate the merits and sound practice of stone cleaning.