There are several methods you can use to clean stonework, including walls. Which one will be most appropriate will depend on the location of your stone wall, what degree of cleaning is required and what kind of stone we’re cleaning.
There are five main techniques we use for cleaning stone:
- Sand jet cleaning
- Dry ice blasting
- Superheated steam cleaning (aka DOFF)
- Sandblasting
- Plain pressure washing
When would you use sand jet cleaning?
Sand jet cleaning works at a low pressure, which makes it ideal for cleaning the stone walls of listed buildings because it causes minimal to no damage to the underlying stone.
The other advantage to sand jetting is that it is a “damp” system, which means the water picks up both the dirt and the abrasive being used to clean. This minimises the dust that’s generated through the cleaning process.
When would you use dry ice blasting?
Dry ice blasting is often best used when we’re cleaning indoor areas because it is probably the most dry dust-free method available – although there will be some dust (all your contaminants will have to go somewhere), there will be less than is created by other cleaning approaches.
This technique works by blasting the surface with solid CO2 particles (the dry ice). The thermal shock is what cleans the stone beneath. Because the ‘abrasive’ evaporates on impact, the process produces less dust.
When would you use superheated steam cleaning?
Superheated steam cleaning (aka DOFF) is suitable for most stone cleaning where risk of damage needs to be minimised and water runoff isn’t an issue.
It works by heating water to temperatures up to 150 degrees C, which softens most paints and provides a powerful cleaning action.
It’s a great way to remove grime, moss and lichen from a wall and we have the ability to adjust the pressure of the steam cleaner, which can make it a gentler process if needed.
When would you use sandblasting?
Traditional sandblasting is a dry technique, which is often most useful if you’re cleaning internal stonework like a floor. Although this approach creates a lot of dust, because it’s dry it is relatively easy to clean up once the cleaning process has finished.
When would you use Pressure Washing?
Traditional pressure washing also has its place in stone cleaning if algae (and, indeed, some paint) needs removing. It is a rapid process, but it can be very aggressive on soft stone, and very destructive on pointing, particularly lime pointing.
