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The Truth About ‘Self-Cleaning’ Glass: How It Works & Why You Need It
The Truth About ‘Self-Cleaning’ Glass: How It Works & Why You Need It
Category: Glazing Guide / Home Maintenance
Reading Time: 8 Minutes
📌 Key Takeaways
- It’s Not Magic: “Self-cleaning” is a slight misnomer. It requires daylight and rain to work effectively, but it significantly reduces maintenance.
- Dual Action Science: It uses UV light to break down dirt (photocatalysis) and water to wash it away in a sheet (hydrophilicity).
- Gravity Matters: The glass requires a minimum pitch (usually 10°) to allow the water to sheet off effectively.
- Ideal for Conservatories: Perfect for large glazed roofs and skylights where manual cleaning is difficult or dangerous.
Nobody enjoys cleaning windows. It is time-consuming, often requires ladders, and inevitably, streaks appear the moment the sun comes out. For owners of conservatories or orangeries with expansive glazed roofs, keeping the glass pristine can feel like a never-ending battle.
It is no wonder that the concept of “self-cleaning glass” sounds almost too good to be true. Is it a marketing gimmick, or genuine innovation?
The answer lies somewhere in the middle. While it won’t completely eliminate the need for the occasional clean, it is a revolutionary technology that drastically reduces maintenance. In this comprehensive guide, KJM Group breaks down the science, explores the market-leading options like Pilkington Activ™, and manages expectations about what it can do for your home.
Table of Contents
1. The Important Caveat: Managing Expectations
Before we dive into the science, we must address the name. The term “self-cleaning” is perhaps a little optimistic. A more accurate description might be “low-maintenance glass”.
For the glass to clean itself, it relies on two natural elements: Daylight (UV rays) and Rain.
If you live in an area with very little rainfall, or during long dry spells in summer, the glass cannot wash itself effectively. Furthermore, heavy, stubborn dirt—like a large amount of bird mess sitting for weeks in dry weather—might still require a quick hose down to help the process along. However, compared to standard glass, the effort required is significant lower.
2. How It Works: The Science of Clean
Self-cleaning glass looks exactly like standard glass, but it features a microscopic coating of Titanium Dioxide fused onto its external surface during manufacture. This coating is integral to the glass and lasts the lifetime of the unit—it won’t wash or wear off.
This smart coating works using a dual-action process:
1. The Breakdown: Photocatalysis
When UV rays from natural daylight hit the glass, it activates the Titanium Dioxide coating. This triggers a chemical process called photocatalysis. This reaction actively breaks down and loosens organic dirt that lands on the surface, such as tree sap, pollen, and bird droppings.
Crucially, this process works even on cloudy days, as UV light is always present during daylight hours.
2. The Wash-Off: Hydrophilicity
This is where the magic happens. Standard glass is “hydrophobic,” meaning water forms into droplets or beads on the surface. As these beads roll down, they leave streaks and dirt trails behind.
The self-cleaning coating makes the glass hydrophilic (water-loving). Instead of beading, rain water spreads evenly across the surface, forming a thin, continuous sheet. As this sheet slides down the glass, it easily rinses away the dirt residues loosened by the photocatalytic process.
3. Reduced Streaking
Because the water spreads into a thin sheet rather than clinging droplets, the glass dries much faster and with significantly fewer streaks, leaving a clearer view.
3. The Importance of Angle (Minimum Pitch)
One critical detail often overlooked is gravity. For the hydrophilic “sheeting” effect to wash dirt away effectively, the water needs gravity to pull it down the glass.
Therefore, self-cleaning glass works best on angled surfaces. Industry standards typically recommend a minimum pitch of 10 degrees. While it can still offer some benefits on vertical windows, it is most effective on conservatory roofs and skylights where the angle and exposure to rain are optimal.
4. Leading Brands: Pilkington Activ™ & Saint-Gobain
Several leading glass manufacturers offer this technology. Saint-Gobain offers the excellent SGG BIOCLEAN range, while Pilkington Activ™ was the world’s first self-cleaning glass, pioneering the dual-action process.
The Pilkington Activ™ Range
- Pilkington Activ™ Clear: Ideal for windows or north-facing conservatories where maximum light transmission is required.
- Pilkington Activ™ Blue: A popular choice for conservatory roofs. Its attractive blue tint offers excellent solar control, helping keep the space cool on hot days.
- Pilkington Activ™ Neutral: Offers the same dual-action cleaning and solar control benefits as the Blue version but with a neutral appearance for more natural light.
5. Dos and Don’ts of Maintenance
Even self-cleaning glass needs care. To preserve the microscopic coating, follow these simple rules:
| DO | DON’T |
|---|---|
| Spray with a hose during long dry spells to help the cleaning process. | Use abrasive cleaners, scouring pads, or steel wool—this will strip the coating. |
| Use soft cloths and warm soapy water if manual cleaning is absolutely necessary. | Allow silicone or solvent-based products to touch the glass surface. |
Frequently Asked Questions
The hydrophilic (water-sheeting) property works 24 hours a day. However, the photocatalytic (dirt-breaking) process requires UV light. While it doesn’t actively break down dirt at night, the coating stores a level of charge from the day, allowing it to continue functioning effectively overnight and into the next morning.
If there is no rain, the UV light will still break down the dirt, but it will remain loose on the surface of the glass. To clear it, simply spray the window or roof with a garden hose. The water will sheet off, carrying the loosened dirt with it.
The coating is fused into the glass surface while it is still molten during the manufacturing process. It is not a spray-on film that can peel off. As long as you do not use abrasive cleaners that physically scratch the glass, the self-cleaning properties will last for the lifetime of the glazing unit.
Yes, you can, but it is most effective on angled surfaces (like roofs) where gravity helps the water sheet off. On vertical windows, the effect is less pronounced, but it will still stay cleaner for longer than standard glass and allow for clearer vision during rain showers.
📚 Explore Our Glass Knowledge Hub
This article is part of our comprehensive series on modern glazing. To see the bigger picture and understand all your options, start here:
🚀 The Ultimate Guide to All Window Glass Types
Or dive straight into our other detailed guides:
- ☀️ Energy Efficiency: The Comprehensive Guide to Low-E Glass
- 🌡️ Summer Comfort: The Complete Guide to Solar Control Glass
- 🛡️ Safety Standards: The Ultimate Guide to Toughened Glass
- 🔒 Security & Silence: Laminated Glass Benefits Explained
- ✨ Low Maintenance: The Truth About Self-Cleaning Glass
- 💎 Crystal Clear Views: Low-Iron Glass (Optiwhite) Explained
Upgrade Your Conservatory Today
Mark Pearce is a highly experienced specialist in the double glazing industry, having built his knowledge from the ground up through hands-on experience in installation, manufacturing, sales, and business management. Beyond his role at KJM, Mark is a keen blogger, writer, and traveller, often sharing insights on the latest innovations in the home improvement industry.
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