Beading Versus True Protection
We see the ads on TV, the internet, and from suppliers to the chimney industry showing great beading. See how the water beads off that wall, floor or chimney? That means that the water repellent must work great. It’s protecting the building. It’s protecting the chimney. But does it provide good water resistance and offer true protection? The answer is simply, “No!”
Beading Is Not the Same as Water Resistance
Unfortunately, beading is not the same as water resistance and those who are experienced in the industry are well aware of this difference. Chemists who have designed and evaluated silicone water repellents know they are not the same and generally not related. The highest performing 100% silane-based sealers designed to protect bridge decks provide excellent water resistance and poor beading. Their performance is demonstrated in difficult testing performed according to the NCHRP (National Cooperative Highway Research Program) and Alberta DOT (Department of Transportation) standards. They protect our highways in the most difficult environments using what are called silane-based water repellents. They don’t provide good beading and they don’t care because true protection is their goal.
Conversely, silicone water repellents for car care are designed to provide outstanding beading, but do not need to reduce water penetration. Here, causing water to sheet off or bead and rum off cars is the objective. They use different kinds of silicones to effectively shed and bead water.
Fortunately, it’s possible to provide both beading and water resistance if the right materials and processes are used. If true protection is your goal, it’s important to know the difference and see the test data that demonstrate water resistance.
Water Resistance in the Field (on the Chimney)
For decades, water resistance has been demonstrated on structures using RILEM, Karsten and MAT tubes. They look alike and provide similar results. Essentially, a tube with volume markings is attached to the structure using caulk, water is added to the tube, and the time is measured for the water level to drop. Products that provide only beading allow the water to penetrate quickly, so quickly that it’s hard to keep the tube filled. Products that provide true protection maintain the water level in the tube with much slower water penetration.
Well-designed water repellents that allow slow water penetration are also designed to allow water vapor transmission so the small amount of water that does go in comes back out when the structure dries (water vapor transmission will be discussed in another blog).
Water Resistance in the Laboratory
It’s also important to be able to measure true protection in the laboratory so we can design and develop excellent water repellents, and more accurately measure the difference between them. Then we can know what water repellents provide true protection.
As noted previously, the toughest methods come from the NCHRP and Alberta DOT organizations. That level of performance is needed for bridge decks and highways, but not for buildings and chimneys. Additionally, the water repellents for those applications need alkalinity from the concrete to cure, which is not always available on walls and chimneys requiring slightly different approaches.
A market leading DIY (Do-It-Yourself) manufacturer has successfully used a test method called the SS-W-110c to evaluate and promote products. Some commercial water repellent manufacturers have also adopted this method. In 2000, this approach was adopted by ASTM becoming ASTM D6532. Essentially coated masonry cubes are placed in ¼” water for 72 hours and the reduction in water uptake versus untreated masonry cubes is determined. This test can work well for DIY products, but it isn’t tough enough to evaluate true protection needed for commercial applications including chimney protection.
To evaluate true protection in the laboratory it’s common in the water repellent industry to utilize a modified version of the NCHRP 244 Series II test. In this case known amounts of water repellents are applied to masonry cubes that are placed under a 1” headspace of water. This is much tougher than placing 2” cubes into ¼” of water. Also, instead of measuring water uptake at 72 hours, this testing involves measurements up to 21 days. It is much more rigorous than ASTM D6532. Water repellents that work well in this testing are far superior and provide true protection. The chart below shows results for commercially available water repellent products for chimneys. At least one of the products that provided no reduction in water uptake has been reported to have >90% reduction in water uptake using ASTM D6532. The chart also contains beading evaluations showing that high beading doesn’t relate to high water resistance or true protection.
Water Resistance and Beading
It is possible to make water repellents that provide both water resistance, true protection, and beading by incorporating the materials into products that already provide the needed performance. While it’s likely that the best beading products will not provide true protection, good beading can be achieved in high performance water repellents.
Why This Matters on the Roof
This discussion may sound academic until you translate it into what happens in a real job. By combining the right silicone chemistries, it becomes possible to design coatings and sealers that provide long-term protection to chimneys. At SaverSystems, our goal has been to bring that level of coating and sealer expertise into the chimney industry through ChimneySaver products.
Winning Matters
Coatings and sealers are chemistry under your brushes and sprayers. When we understand that chemistry, we elevate protection to the rooftop.