The Yellowing of Aberdeen

We've already commented upon the disgusting yellowing of some buildings in Aberdeen, and the possible mechanism which is causing it.

Unfortunately, the more you look, the more you see...

Yellowing window and door architraves in West End terrace

Albyn Grove - tenement flats yellow, commercial unit below (uncleaned) grey.

Bon Accord Street. The rough finishing on the blocks has taken on a mottled yellow appearance. It looks like lichen from a distance. But it isn't - the stone itself has changed colour.

Holburn St, shop units and 1st floor yellow. 2nd floor (uncleaned) grey.

By chance, we were looking at Aberdeen City Council's Local Plan, where we found in Chapter 3, Policies (PDF) that abrasive, chemical or high pressure water cleaning of listed buildings or buildings in conservation areas will require special permission under Policy 15 of the plan.

Is it the case that - this explicit policy referring only to abrasive, chemical and high pressure cleaning techniques while omitting laser-cleaning techniques - it has cleared the way for unrestrained laser-cleaning of these buildings? The yellowing effects of imperfectly-tuned laser cleaning systems are well known, and, indeed were studied in the 1990's by Aberdeen's own Robert Gordon University.

It is regrettable that the words 'laser-cleaning' were omitted from the Local Plan policy. The disastrous effects are clear for everyone to see.

Perhaps we are wrong, we're certainly not claiming any expertise on stone-cleaning techniques and their effects. But one thing is certain. Something has gone horribly wrong.