Over the years at Presto Restoration Products & Services, we have witnessed countless commercial buildings with precast sealed with silane. This material performs poorly, causes stains on glass and metal surfaces and is harmful to the environment. Unfortunately, the water repellent most commonly used today to seal architectural stone consists of 40% solid content silane. In our experience, 40% silane is one of the least effective product options available for vertical precast surfaces, especially when flush-mounted windows are present. It is also important to understand the disadvantages of applying silane so informed choices can be made regarding the right product to protect precast: Silane is an organic oil that is UV and heat-sensitive – When the atmospheric elements connect with silane-protected surfaces, their molecules degrade and leach out of the building materials, decreasing the protection on the surface and causes stains on adjacent architectural surfaces. Stone is a breathable, porous material – Stone surfaces that are protected by silane are still breathable and allow the molecules to exit the stone material freely. However, after the stone is heated by the sun and cooled again, it breathes allowing moisture and silane oils that have not bonded with the stone’s silica to leach out and reside on other building surfaces. Then it absorbs dry, airborne materials such as dust and dirt that are also made of silica. This triggers the reaction that causes the silane to turn into a resinous, repellent material on unintended surrounding surfaces. This is a major cause of hard-water stains, the worst type of stain on glass. Surfaces sealed with silane materials offer poor surface protection – Water is allowed to penetrate the surface of the “protected” stone immediately, causing contact with the stone. Under the surface, the stone is protected; however on a high-rise building, it is more important to consider the protection – and appearance – of the outermost layer of the stone material. Silane is organic and breaks down rapidly, attracting pollutants that eventually wash down the building – This waste collects around the base of the building where it resides in high concentrations, often near public seating and eating areas. Building sealed with silane need to be recleaned and sealed every 2 to 3 years while building sealed with LeachStop don’t need to be cleaned for at least 10 years. So What Is the Alternative? High performance silicone precast protection hardens to a silicone caulking like material that takes far longer to break down than silane and thus last much longer for protecting your building. Presto’s LeachStop.® is a more suitable material, has superior surface protection, last 10 times as long and doesn’t cause stains on architectural surfaces, as a matter of fact its designed to help to prevent them by preventing erosion of the precast surface. This product is highly ultraviolet-resistant, repels water, as well as oil and many types of environmental staining. Learn more about Leach Stop® and its superior results for your building and our environment.