Best practices for soft wash cleaning sandstone

September 03, 2019

Best practices for soft wash cleaning sandstone

If patios and paths have been neglected for many years, lichen can grow deeply into the surface and be very hard to remove.

Because sandstone is a relatively soft stone it is not advisable to use high pressure jet washing. This can damage the surface layer of the sandstone and if live growths are present will rip out the roots, further damaging the soft sandstone.


Soft washing sandstone with Benz Lightning Cleanze & Tornado Cleanze

1. Give the sandstone a light, low pressure, power wash prior to treating with Lightning Cleanze biocide. This will clear loose matter from the surface and remove some of the more shallow-rooted growths. Preparing sandstone for a soft wash treatment like this will allow the "perfect partners" of Lightning Cleanze and Tornado Cleanze to work together, faster.

2. Treat the sandstone with Lightning Cleanze biocide (5:1) to kill the algae and lichen that are usually responsible for making sandstone look "dirty".

3. Apply Tornado Cleanze liberally by brush – as a post-treatment "spot cleaner" – to areas of deep residual staining and leave for 15-60 minutes to activate. Use a medium soft brush to brush-in Tornado Cleanze. A 9 inch brush can be useful for awkward areas. For very heavy staining (e.g. by black lichen, "black dots"), you may find a slightly stiffer brush useful.


Quick tips:

  • Set your jet washer to low pressure if you have a variable control, and/or fit with a fan jet, and hold well back from the surface.

  • We've found that a light jet wash is more effective than sweeping the surface clean of loose matter, or using a blower.

4. Giving a biocidal treatment with Benz Lightning Cleanze biocide, to kill the growths and sanitise the sandstone prior to cleaning with Tornado Cleanze, can produce the most effective results. This also serves to pre-wet the surface, making the application of Tornado Cleanze easier, quicker and more effective.

5. Sandstone can be slower to come clean than hard stone like granite. This is why some "less than ethical" contractors employ high pressure washing, and dangerously high concentrations of sodium hypochlorite, to quickly produce a "Wow!" result that impresses customers who know no better.

In their pursuit of a fast buck they ignore the damage they do to their customer's property and the harm that long-term chlorine exposure does to their, and their employees, lungs. They rarely get repeat business ...

6. Complete the treatment of sandstone with an application of Benz Bio Cleanze (Max 50:1 if children & animals will walk on the sandstone, otherwise apply at up to 20-30:1 dilution).

Determine the strength at which to use Bio Cleanze by assessing factors such as a) how long since the sandstone was last cleaned b) how bad the colonisation of the sandstone is c) the local environment.

Quick tips:

1) Bio Cleanze continues to deep clean porous surfaces such as sandstone for several months following a treatment.

2) Bio Cleanze imparts a degree of residual protection against re-colonisation to sandstone that neither jet washing nor any sodium hypochlorite product/mix can offer.

Click here to get more practical soft washing how-to tips

How to find answers to most soft washing questions: Simply enter a relevant "keyword" or short phrase – e.g. keyword for the above link = "how to" – into our in-site Search Engine (magnifying glass icon on the main menu).

You can order Benz Softwash chemicals & equipment online or by phone:

GB (England, Scotland, Wales)

Phone: 0800 70 74 222 


Ireland and other countries

Phone: 00353 214 622 978


Lines open Monday - Friday, 9am – 5pm

Please note: The above numbers are for orders only (click here for tech support)

We hope this information is helpful and sincerely wish you great success in your soft washing business,

Ben, Leo, Fiona, Stevie & Anthony

PS: After completing the first soft wash treatment, put your customer on a "Clean & Maintain" ongoing maintenance programme. Your customers will enjoy a permanently clean property and you will enjoy a steady stream of repeat business.

This is clearly a win-win arrangement for both customer and contractor.


Click here to explore the extensive range of Benz softwash cleaning chemicals & equipment

Benz Softwash Bio Cleanze DDAC biocide & Benz Softwash Lightning Cleanze SH sodium hypochlorite biocide

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