The problem

A team of SSH conservators and masons were tasked with addressing the deteriorating stonework through the removal of sulphation crusts and deposits, stabilising the decaying stonework and mortars, and re-establishing weathering’s in order to slow future decay. The biggest challenge for this project was the sulphate skins (or carbonation crusts) which commonly occur in sheltered positions where the building design prevents natural wash-down by rainfall.

The solution

Restorative Techniques conducted trials prior to the works beginning on site, and returned again to advise on the quantities of materials and systems to be used.

ThermaTech was used initially, but due to the high levels of crustation and the soft nature of the stone a nebular spray system was then used. This achieved better results in this case; lifting crustation and offering a very controllable cleaning solution, the nebular spray also reduced the amount of poulticing required.

The outcome

SSH conservators purchased a nebulous boom system and poulticing products. By adapting the processes, the sulphation was efficiently removed whilst preventing over-saturation of the stone work. As a result the original surface of the stone was revealed without damage to the building.

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