This informal CPD article, ‘The Science Behind Softwashing – Why It’s More Than Just Cleaning’, was provided by SoftWash UK, who offer professional softwashing services. They are committed to advancing the field of softwashing through continuous innovation, education, and reliable customer service.
Introduction
Softwashing is advancing exterior cleaning by offering a safer, and potentially more effective alternative to pressure washing. This method not only cleans surfaces but also eliminates organic growth at the root, preventing rapid regrowth. Unlike traditional pressure washing, which relies on force to remove dirt and biological growth, softwashing utilizes specially formulated cleaning agents that break down contaminants at a molecular level.
The effectiveness of softwashing is based on science—specifically, the chemistry of cleaning agents, the role of surfactants, and the correct application techniques. By understanding how these elements work together, professionals can achieve long-lasting, environmentally responsible results without damaging delicate surfaces.
In this article, we’ll explore the key scientific principles behind softwashing, including the chemistry of its cleaning agents, its best application practices, and important environmental and safety considerations.
The Chemistry of Softwashing
The primary reason softwashing is an effective alternative to pressure washing lies in the chemistry behind its cleaning solutions.
The Role of Sodium Hypochlorite (NaOCl)
- The active ingredient in most softwashing solutions is sodium hypochlorite (NaOCl), a powerful oxidizing agent. It effectively eliminates organic matter such as:
Algae – The green or black discoloration commonly seen on roofs, patios, and render. - Mold and Mildew – Fungi that thrive in damp conditions, particularly on shaded walls and decking.
- Lichen and Moss – More stubborn growths that attach deeply to porous surfaces like stone and concrete.
How Sodium Hypochlorite Works
When applied to a contaminated surface, sodium hypochlorite breaks down organic material at the cellular level. It disrupts the biological processes of algae and fungi, killing them at the root rather than just removing their surface layer (as pressure washing does).
Once the organic matter is broken down, a low-pressure rinse removes the debris, leaving a cleaner and longer-lasting finish. Because the spores and root systems of contaminants are eliminated, surfaces remain cleaner for months or even years without the need for frequent re-treatment.
The Role of Surfactants in Softwashing
Surfactants are another crucial component in softwashing solutions. These compounds lower water’s surface tension, allowing the cleaning agents to:
- Adhere to surfaces longer – This prevents the solution from running off too quickly.
- Penetrate porous materials – This ensures deep cleaning rather than just surface-level removal.
- Break down stubborn grime and oils – Making it easier to rinse away.
Surfactants are often used to help softwashing solutions spread more effectively over surfaces, particularly on vertical structures like walls and roofs. By improving adhesion, surfactants ensure that the cleaning agents stay in place long enough to fully break down organic contaminants.
Application Techniques and Best Practices
Softwashing requires a very different approach compared to pressure washing. High-pressure jets can cause damage to surfaces, particularly on delicate materials like:
- Render and stucco – Can erode or crack under high pressure.
- Roof tiles and shingles – Can be dislodged or have their protective coatings stripped away.
- Wood and composite materials – May splinter, warp, or suffer water damage.
Softwashing eliminates these risks by using low-pressure spray systems that gently apply the cleaning solution.
The Importance of Dwell Time
One of the most important factors in successful softwashing is the dwell time—the amount of time the cleaning solution remains on the surface before rinsing.
Dwell time varies depending on the surface and contamination level:
- Light organic staining: 10–15 minutes.
- Moderate algae or mold growth: 20–30 minutes.
- Heavy lichen and black spot removal: 45–60 minutes.
Allowing the solution to dwell properly ensures that contaminants are fully broken down rather than just partially removed. However, it’s important not to let the solution dry on the surface, as this can leave streaks or cause uneven cleaning.
Rinsing and Post-Cleaning Treatments
Once the dwell time is complete, the surface is rinsed with low-pressure water. This removes the broken-down contaminants while protecting the surface from damage.
To extend the longevity of the clean, many professionals apply a biocide after softwashing. Biocides such as DDAC (Didecyldimethylammonium Chloride) can prevent regrowth of algae, mold, and moss for up to a year or longer.
Pressure washing only removes surface dirt
Environmental Considerations and Safety
Softwashing, when done correctly, is a more environmentally friendly alternative to pressure washing. However, improper chemical handling can pose risks to plants, wildlife, and water sources.
Best Environmental Practices
- Use biodegradable surfactants to minimize chemical impact.
- Control runoff to prevent chemicals from entering drains or water sources.
- Pre-wet surrounding plants to dilute any accidental chemical exposure.
By following these steps, professionals can ensure that their softwashing practices are effective while also being environmentally responsible.
Safety Measures for Softwashing Operators
Softwashing solutions contain strong chemicals that require proper handling and safety precautions. Operators should:
- Wear protective gloves and goggles to prevent skin and eye contact.
- Use respiratory masks when working in enclosed areas or with high concentrations of chemicals.
- Store chemicals properly in a cool, dry area to maintain their effectiveness.
Additionally, proper training is essential for anyone using sodium hypochlorite-based cleaning solutions. Understanding correct dilution ratios and application techniques prevents overuse, surface damage, and unnecessary chemical exposure.
Softwashing vs. Pressure Washing – Why Science Matters
Many property owners assume that pressure washing is the best way to clean exterior surfaces. However, pressure washing only removes surface dirt—it does not address the root cause of organic staining.
Key Differences:
Softwashing:
Method: Uses low-pressure chemical application.
Effectiveness: Kills algae, mold, and bacteria at the source.
Surface Safety: Safe for delicate materials like render and roof tiles.
Longevity: Provides a deep clean that lasts months to years.
Pressure Washing:
Method: Uses high-pressure water jets.
Effectiveness: Removes surface grime but doesn’t prevent regrowth.
Surface Safety: Can cause erosion or structural damage.
Longevity: Often requires more frequent re-cleaning.
By applying scientific principles—specifically oxidation, surfactant action, and controlled application—softwashing can outperform pressure washing in both effectiveness and long-term results.
Conclusion
Softwashing is more than just an exterior cleaning method—it is a science-based approach that ensures long-lasting, deep-cleaning results while protecting delicate surfaces. By understanding the chemistry of sodium hypochlorite, the role of surfactants, and the importance of proper application techniques, professionals can deliver cleaning services safely and effectively.
More than just removing dirt, softwashing prevents regrowth, reduces the need for frequent maintenance, and provides a sustainable, environmentally friendly solution for exterior cleaning.
As more professionals embrace the scientific principles behind softwashing, the industry continues to shift toward a safer, smarter, and more effective cleaning standard.
We hope this article was helpful. For more information from SoftWash UK, please visit their CPD Member Directory page. Alternatively, you can go to the CPD Industry Hubs for more articles, courses and events relevant to your Continuing Professional Development requirements.
