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.
Btw: Our knowledge of chemistry, on which this article is based, came from an in-depth conversation with a senior industrial chemist back in 2014.
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.
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.
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.
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 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.
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.