One of the favoured ways of cleaning stone buildings and monuments is with superheated water. It effectively and quickly cleans off all kinds of contaminants, including many paints – and when it removes paint it does so without leaving traces behind embedded in the stone.

The producers of the two main systems used in the stone industry – Stonehealth’s DOFF and Restorative Techniques’ ThermaTech – have both improved their systems.

Restorative Techniques have coupled their system to a recovery system that collectes the superheated water and the dirt it has cleaned off, then condenses and filters the water.

This makes the system particularly clean for use in interiors, as well as considerably reducing the water vapour in the atmosphere that can be a problem in confined spaces. Each system can be used by two operators at the same time.

Stonehealth has redesigned DOFF, making numerous modifications that make it more compact and easier to manoeuvre and use.

These developments and other systems are included in the report on stone cleaning in the November issue of Natural Stone Specialist magazine.