There are a few different types of flagstone sealers to use, and a few different flagstone sealers to avoid. The best flagstone sealer for your flagstone comes down to what you want your flagstone to look like once sealed, and what you need the flagstone to offer in terms of performance.
Penetrating sealers are the most popular category of flagstone sealers. They penetrate into the flagstone where they create a hydrophobic barrier within the pores. They don’t leave a visible surface film, and there isn’t a coating to maintain. Surfaces sealed with a penetrating sealer are better protected against damage and deterioration caused by water absorption such as crack, spalling, staining, and the growth of mold and mildew.
Under the category of penetrating sealers, there are a few different sealers to choose from. There are Silane-Siloxane water repellent sealers like the Armor SX5000 and Armor SX5000 WB. These sealers won’t change the look or color of the flagstone. The second type of penetrating sealer is the Armor WL550. The Armor WL550 works entirely below the surface, but it will also slightly enhance the color of the flagstone to bring out any dull and faded coloring.
A second type of flagstone sealer is an acrylic sealer. Acrylic sealers aren’t commonly used on flagstone however because they have a high failure rate. The flagstone doesn’t offer a good bonding surface, and they differ greatly from acrylics when it comes to expanding and contracting due to temperature differences. Often times applying an acrylic sealer to flagstone will result in delamination and coating failure, and the acrylic sealer will have to be removed. Everyone loves a glossy surface, and acrylic sealers offer that, but if you choose to apply an acrylic sealer to flagstone, be away that it may need to be removed if it fails.
The best way to determine which flagstone sealer you want is to apply the sealer to a test area. This will show what the sealer will look like when applied to your flagstone. If you still have questions, feel free to contact a Foundation Armor technician.