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The Renaissance Hotel, which was previously the Midland Grand Hotel that opened in 1873 is attached to St Pancras Station and its front façade is often mistaken for the station. Over its life span the structure has been exposed to endless industrial pollutants mainly from coal burning activities resulting in ‘smogs’.

This impressive building has particularly suffered from the railway station where the Barlow Shed contained high concentrations of smoke from the coal burning steam trains. Coal burning creates sulphates, nitrates, ammonia, sodium chloride, carbon and mineral dust. When the Midland Grand Hotel was cleaned in the early 1990’s by Stonehealth’s JOS system (which has now been superceded by the improved TORC system) it was evident that there was considerable salt activity throughout the whole façade.

Other methods of cleaning which were tested at that time included those of chemical or the use of voluminous amounts of water which activated the various salts hidden in the pores below the surface. These salts then migrated to the surface producing unsightly, unacceptable levels, of efflorescence.

Dormant latent salts can also be activated if the environmental equilibrium is altered by temperature or humidity. It is therefore expected that where there is a concentration of salts below the surface, as there is at what is now known as the Renaissance Hotel, even when they are removed efflorescence can subsequently reoccur. Poulticing is the traditional conservation method of removing salts but this would be an expensive, long and arduous process which could be inconvenient for the hotel. Regular use of the Stonehealth DOFF system will gradually assist the reduction of salt activity, possibly eventually to a level where it will no longer be a problem.