Granite can also be cleaned with a pressure washer. However, there are some properties and sensitivities to be taken into account that come with this natural stone. The nature of the surface also plays a role. Polished granite indoors reacts completely differently than rough fencing and patio slabs outdoors.
Opinions range from rejection to recommendation
Cleaning granite with a pressure washer is not without controversy among experts. While some voices recommend a cleaning that is as deep as the pores, others warn against the creation of additional pores and a washing-out effect.
In general, the pressure must be adjusted when cleaning natural stone with a high-pressure cleaner. Granite can suffer mechanical damage if the water pressure exceeds 150 bar. Ideally, 100 bar should not be exceeded and an attachment brush should be used.
Cleaning agents and additives
Granite is extremely sensitive to almost all acids. An exception is aminosulfonic acid, which helps against lime stains on granite. However, it should only be used in very diluted form and, if possible, in a horizontal direction. Otherwise, only alkaline cleaning additives can be used, which can be added to the water of the high-pressure cleaner.
The following procedures protect granite and ensure more effective cleaning results with the least possible use of force:
- Clean only at ambient temperatures of twenty to thirty degrees Celsius.
- If necessary, switch on the heating function of the pressure washer.
- Distribute the force on the stone as horizontally as possible.
- Intensify the cleaning effect by exposure time (caustic solution) and only “rinse”.
- Allow reaction times of up to two hours
- Alkaline cleaning agents and additives should have a pH value below 10.5
- Sealing and impregnating granite is just as controversial as high-pressure cleaning
- Many dishwasher tabs are a helpful home remedy for cleaning
If larger granite surfaces are found outdoors, it may be worthwhile to hire or purchase a scrubber-dryer instead of a pressure washer. The cheapest machines cost from around 300 pounds. With special PPN round brushes, granite can be cleaned much more gently than with a high-pressure cleaner. A pressure washer should not be used for more than two cleaning cycles a year. A scrubbing machine can be used every few weeks without any problems.