Should you "spot treat" with Lightning Cleanze AFTER applying Bio Cleanze? (Part 1)

September 25, 2018

The short answer, in our experience and understanding, for the most part is No - treat with Benz Lightning Cleanze first, until the surface is as clean as reasonably possible, then treat with Benz Bio Cleanze.

Quick tip: Our knowledge of chemistry, on which this article is based, came from an in-depth conversation with a senior industrial chemist back in 2015.

Where did the idea of spot treating come from?

We think the idea of spot treating with Lightning Cleanze after treating the entire surface with Bio Cleanze emerged from a well intentioned desire to minimise the use of sodium hypochlorite.

And we further believe that this practice arose from a mistaken impression that, because Lightning Cleanze contains sodium hypochlorite, it is as dangerous as using illegal, unapproved, high available chlorine hypo mixes.

The truth is that, correctly applied at the correct dilution, Lightning Cleanze is not a threat to our environment. So let's look a little deeper at the chemistry of softwashing.

Why treat a surface with Bio Cleanze after treating with Lightning Cleanze?

The the aim of treating with Bio Cleanze is to kill any remaining spores that Lightning Cleanze may have left behind, as its chemical nature enables it to penetrate surfaces more deeply. It continues the cleaning action begun by Lightning Cleanze over several months and imparts a level of residual protection against re-colonisation.

The reason for thoroughly rinsing Lightning Cleanze from a surface prior to treating with Biocidal Wash is to remove as much of the remaining surfactant as possible. If left, the surfactant can chemically react to, and inhibit the action of, Biocidal Wash.

So, because of the chemical nature of the two biocides, it makes no sense to put Lightning Cleanze on top of Biocidal Wash. The only exceptions – other than sand and cement render (see below) – which will be rare, would be if this was absolutely essential because of a demand by a customer, a mistake during application, or some other unforeseen circumstance.

Quick tip: Fairly obviously, if a few dark patches or streaks remain after treating with Lightning Cleanze, it's fine to spot treat those areas prior to treating with Bio Cleanze.

The problem with spot treating

We've never been happy with the procedure of spot treating with Lightning Cleanze after treating a surface with Bio Cleanze. Contractors who do this are ignoring the fact that no difference will likely be seen for 12 months or so.

But at around this point in time the algae growth on the areas that were spot treated will almost certainly be greater than on the surrounding area. This is because the first application of Bio Cleanze will be mostly gone after another application and rinsing of Lightning Cleanze.

Doing this will have largely negated the residual protective effect of Bio Cleanze, which will have been minimised in the areas that were spot treated, allowing the increased re-growth of algae on those areas.

The hidden costs of spot treating

If knowledge of the chemistry involved is not enough to deter you from spot treating as a matter of course, let's consider the "hidden costs" of spot treating.

Having to travel back to a job to re-treat it doubles up on fuel costs and wear and tear on your vehicle. There's also the time cost involved in traveling: setting up and packing up your gear twice, cleaning up your customer's property twice, and so on. This all consumes time that you could have spent getting paid for working on another job.

And let's think about the environmental cost. Motor vehicles are one of the largest polluters of our planet, so when a contractor has to drive to a customer multiple times the cost to our environment of the added pollution from the vehicle is also multiplied.

The one exception: sand and cement render

The exception to the rule of treating of treating with Lightning Cleanze first and Bio Cleanze second is when softwashing a sand and cement render that should have been painted (painting helps protect the sand and cement render from colonisation by biological growths).

These unpainted renders are often heavily colonised and require deep cleaning before painting. Because of the porous nature of sand and cement renders, they can be tough to clean when they've not been touched for several years, which has allowed the deep colonisation of biological growths such as algae and lichen.

Because of its low surface tension, and hence better "wetting" characteristics, Bio Cleanze will soak deeply into the render, killing spores that other biocides can't reach. Then follow up with a treatment of Lightning Cleanze diluted 5:1 a couple of months later.

This approach has proved to be both the most effective and the easiest method, ensuring the surface is as clean as possible just prior to painting.

Important: Ideally the surface of a sand and cement render must be rinsed a few days prior to painting, or at the very most a week or two before. This ensures the surface is as clean as possible, dust and cobwebs are removed, and the surface has time to dry out.

Not rinsing would leave traces of softwash chemicals and organic matter. Therefore it's best to rinse once, just before painting, and let nature do the heavy cleaning for you via Bio Cleanze. This approach means much less chemical and hard work will be needed.

Here's the sequence for softwashing sand and cement render

  1. Remove any loose organic material by brushing or a very light pressure wash.
  2. Apply Bio Cleanze at 25:1.
  3. Wait a couple of months for the surface to self-cleanse through natural weathering.
  4. Apply Lightning Cleanze at 5:1.
  5. Rinse thoroughly as close to the time of painting as is practicable.
  6. When dry it will be ready for painting. All biological growths will be gone, as will all traces of softwash chemical – leaving a sterilised surface ready for the painter.

In summary, except for softwashing sand and cement render (and a few, very rare instances where a "less than perfect" cleansing effect is achieved from the first treatments), we can find no valid reason to spot treat with Lightning Cleanze after treating with Bio Cleanze.

Applying Lightning Cleanze again to spot treat small areas will only inhibit the residual protective effect of Bio Cleanze in those areas. In general, the correct procedure is to apply Lightning Cleanze first and Bio Cleanze second.

We hope this information is helpful.


Ben, Leo & Fiona

PS: Click here to read a Benz Trade Tips article on the how-to of soft washing painted surfaces

Click here to explore the full range of Benz 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

How to safely soft wash asbestos roof slates, tiles & sheeting
How to safely soft wash asbestos roof slates, tiles & sheeting

September 15, 2021

Many soft wash contractors can be unsure of the safest way to soft wash asbestos roofs. So in this post we lay out the best practices we've learned from running a soft washing business since 2013.

Click the link on this page to learn how to treat asbestos ...

View full article →

How to soft wash natural slate roofs
How to soft wash natural slate roofs (video)

September 08, 2021

Ben demonstrates how to scrape moss and lichen from natural slate roof tiles and treat the biofilm to kill all the growths on this natural slate roof.

Click the link on this page to watch the how-to video ...

View full article →

Soft wash brush application
How to protect lead flashing & roofs when soft washing (video)

September 02, 2021 2 Comments

When soft washing it's vitally important to protect surrounding building materials. e.g. lead flashing. And not to create "clean streaks" – from overspray and run-off – on surfaces that are not part of your contract.

Click the link on this page to watch how we achieve this when soft washing a chimney ...

View full article →