When thinking of the different types of protective coatings offered in the industry, it’s easy to assume they are all the same.
As long as the water rolls off the glass when it comes into contact with the applied surface, it should be okay, right?
Although the sole purpose of any water-repellent coating is to keep water from sticking to the glass, there are certain characteristics any glass fabricator, applicator or consumer should be looking for when considering a protective glass coating.
In this post, we will focus on two characteristics that precisely measure the performance and effectiveness of your protective glass coating: Sliding Angle and Contact Angle.
1. Sliding Angle
In its simplest explanation, sliding angle measures the slickness of a surface – whether coated or not. For years now (and even today), determining the performance and effectiveness of a protective coating has been done by using contact angles measured in degrees of its water repellency.
And while contact angle is a good standard measurement, to determine how easy to clean a surface or coating is we must look at its sliding angle.
Here’s an idea of how it works:
Put a drop of water on a piece of glass and slowly start tilting the glass. The quicker the drop of water slides down the tilted surface, the lower the sliding angle is. The lower the sliding angle is, the slicker the glass surface must be. And the slicker the glass surface is the easier it is for water to slide right off.
However, if you’re more of a visual learner, think of how water easily slides off of a lotus leaf. The water comes into contact with the leaf and because of its hydrophobic characteristics, the water immediately beads up and rolls right off.The same concept applies
This same concept applies to your glass treated with a water-repellent coating.
So, how does this help you and what does it mean in terms of performance?
Sliding angle is a great measurement that indicates how easy it will be to clean the water or debris that sticks to the surface of the glass or glass-like surface. And not only how easy it is to clean, but also how often you’ll have to clean the surface.
Think about it. The slicker the surface of the glass, the less often water, dirt and other contaminants can stick, and so the less often cleaning is required. So when comparing coatings, the lowest sliding angle is the easiest to clean.
Conversely, and worthy of note, is that if a glass surface has a higher sliding angle (not as slick), then the surface will be stickier – resulting in a harder to clean surface, that you’ll have to clean more often.
So, make sure that any protective coating you apply to your glass has a low sliding angle.
2. Contact Angle
For those of you who are unfamiliar, contact angle simply measures how high a bubble of water stands on a surface.
Accordingly, the more water-repellent a surface is the higher the contact angle will be, making it easier for water to bead off the glass and harder for minerals and contaminants (such as body oils, soap, etc.) to be deposited on the glass.
While both contact angle and sliding angle are individually good measurements for the effectiveness of water-repellent coatings, when considered together, they become much more powerful.
A higher contact angle tells how much less a surface will be stained, while a lower sliding angle tells us how easy it will be to clean the surface, as well as lower the number of times you have to clean the glass.
So next time you are considering which type of protective glass coating (water-repellent coating) you want on your glass, remember to ask your sales representatives about these two important characteristics.