How to softwash red algae stains on render

May 30, 2018

Benz Softwash supply softwash chemicals to the professional softwash cleaning trade

We've been asked about the best way to softwash red algae stains from wall render.

After softwashing, light red algae will go from wall render in a few days in warm weather and up to two weeks in winter.

Heavy dark red algae on render can be problematic as it often has multiple layers of black algae underneath. So be prepared to give multiple softwash treatments.

Benz Bio Cleanze – when used as a stand-alone softwash treatment at up to 25:1 dilution – will clean red algae from wall render in a few months. A second application after a month or so is often advisable to remove any remaining red algae stains.

The fastest results come from softwashing the worst of the red algae with Benz Lightning Cleanze at 5:1 dilution (go to 4:1 if test results indicate this to be necessary but take care and use full ppe as it is getting quite strong at that dilution).

Then follow up with a treatment of Bio Cleanze, after thoroughly rinsing Lightning Cleanze from the wall render, at 40:1 dilution. Biocidal Wash will continue cleaning the red algae through time and impart residual protection against recolonisation.

Click here to learn more about softwashing wall render on our dedicated render page

Click here to read a more in-depth article on softwashing red algae from wall render

We hope this information is helpful.


Ben, Leo & Fiona

Click Here to explore our popular softwash cleaning products

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

Leave a comment

Comments will be approved before showing up.

Also in Benz Trade Tips

Softwash chemical application kit
Are pencil jets or fan jets best for soft washing brushes?

July 21, 2021

We use pencil jets in our brushes because we've found they don't clog or break as much as fan jets.

In the case of the Gardiner 45cm brush we use four of them. We turn the pump down so the flow rate is acceptable and does not produce much run-off.

Flow control at the pole is still critical however. Click the link on this page to learn about the solution we've found to be so successful ...

View full article →

Soft washing at heights - your problems solved! (how-to video)
Soft washing at heights - your problems solved! (how-to video)

July 15, 2021

Watch Ben use his innovative pole trigger to safely and efficiently treat wall render. This patent pending trigger enables you to  work more efficiently, with less effort and far less strain on your body. Click the link on this page to watch our how-to video >>>

View full article →

Benz Bio Cleanze, DDAC based softwash biocide
Do you know why we add IPA (Isopropyl Alcohol) to Bio Cleanze?

July 10, 2021

Some customers have wondered why we add IPA (Isopropyl Alcohol) to Benz Bio Cleanze. So we thought we'd clear this up and clarify the situation once and for all.

Click the link on this page to read the full Trade Tips post ...

View full article →