The Talbot Hotel in Malton, Yorkshire required gentle cleaning of soot staining from the historic Hildenley limestone frontage during refurbishment in 2012. I used sodium bicarbonate in a technique that was first developed to clean the Statue of Liberty and which is now gaining wider recognition for potential to remove dirt from the pores of stone without abrading the surface of the stone itself.
The sodium bicarbonate crystals burst on impact and thereby cut into the dirt and then laterally disperse taking waste away with the air blast before hitting the matrix of the stone itself. The owners wanted someone who understands stone textures and who could apply the technique effectively but without risking stone or other features. The upper storey came out a slightly different hue, it appears that different beds of stone were used in adding a later floor to the building.
The 18th century palladian New Wardour Castle (below) was converted from a school to private accommodation and music studios in 1994. I cleaned the gallery stone staircase as well as laying new local limestone floors to original standards. This cleaning involved fine abrasives and chemical cleaning to remove paint and adhesive from the limestone treads.
The cleaning below is a recent task – removal of paint from Hereford sandstone cills. The hard synthetic paint and underlying traditional paint is being removed by refinishing the dressing of the stone. This method treats the paint as though it were the last millimetre of original finishing, it can be rubbed to a smooth finish or left with chisel finish as in the images below. This does not lead to an uneven and deeply worn surface which would occur with grit blasting or machine dressing – due to the varying density of paint and stone layers. These cills, all exposed surfaces, were re-dressed by hand in about two hours each. This can come down to well below an air using air tools but the control is less and the cut slightly deeper.