The simplicity of water-based steam cleaning can be appealing, but repeated use of too much super heated water can lead to risks of residual staining, mobilisation of salts and corrosion of hidden particles of Iron within some limestone surfaces.

Surface of a Limestone magnified by 120 microns

Steam can penetrate the small cracks and fissures on the surface of the limestone.
This does clean the limestone, but will also embed water into the surface.
Repeated cleaning using a steam cleaner can activate salts and weaken the stone over time. This can also lead to spalling or fragmentation of the surface.

COMPROMISED SEALER?
Surfaces that have been treated with an impregnating sealers can also be compromised. Steam cleaning does not normally remove the impregnating sealer, however repeated use can expose new fissures and capillaries within the stone. The newly exposed and unsealed surface takes in more dirt and becomes harder to clean, which then…