The church was heavily bombed during the Second World War, although Wren's iconic spire largely survived. It was, however, suffering from very heavy sulphation (in excess of 25mm), and SMB was contracted to undertake the removal of this.
Our initial approach was to carry out timed nebulous spraying techniques to soften the soiling prior to using the Therma Tech and Vortech systems. It became apparent quite quickly that the internal sulphation had an insoluble resin like property, unlike the external soiling which responded to the nebulous method. We were able to remove the majority of the soiling using hand tools, followed by the super heated steam to remove any underlying soluble soiling.
The Vortech system was adopted for the removal of the final layers in conjunction with Aluminium Silicate 250 media. Working with three units simultaneously within the confines of the spire was a challenge, with each cleaner needing to to adjust their own pressure and media flow rate to suit the changing tenacity of the soiling encountered.
By adapting the processes to the needs of the building, we were able to make up lost ground and efficiently remove the sulphation whilst avoiding over-saturation of the stone work, thereby preventing rust staining. As a result, the original surface of the stone was once again revealed with the patina and masons tooling marks still intact.
Hopefully through preventative periodic maintenance washing, such excessive levels of soiling will not be encountered by future generations of cleaners entrusted with the task of retaining our heritage.
Our products have been used to restore a wide variety of buildings