How to Seal Natural Stone

02 Oct, 2019

It can be intimidating, and a bit confusing, trying to figure out how to seal natural stone, or even whether you should. After investing in such such a beautiful new product, of course you want to make the right decision, and care for your new stone properly, and ErthCoverings is proud to help guide you in that decision making process.

Should you seal your stone?

ErthCoverings products are virtually maintenance free. Occasional washing to remove dust and dirt build-up is all the product requires, but a professional grade natural stone penetrating sealer may be used on ErthCoverings stone veneers. Indeed, some products should be sealed if you intend to install them outside, or in any application susceptible to staining, to protect the stone and allow for easy cleaning. This is especially important in high traffic areas. Any area prone to oil stains, smoke, soot, dirt, grime or water splashing would benefit greatly from a sealer. 

If you do decide to use a sealer you should make sure it is a breathable one, and that it is suitable for the type of stone you have chosen. Different stone types have different levels of density, porosity, permeability and absorption. Each type of stone is different, and they each need to be treated as such, but because all natural stone is porous, a penetrating and non-film forming sealer should be used so that it can penetrate deep within the stone and repel water from more than just the surface layer. 

Consult the recommended sealer listed for your specific product, or the manufacturer, if you need more guidance when it comes to selecting a sealer. You should take note that sealers may enhance the colour of the stone, and that a sealer may also slow the natural movement of moisture out of the stone, and increase efflorescence and/or spalling. You should always test any application on a sample of stone to determine the desired look and performance before continuing with a larger application.


The application process

When applying the sealer to your stone, you should carefully follow the instructions provided by the specific manufacturer of the sealer you have chosen, but there are some basic guidelines that you can follow.

First, you should always seal your stone before applying your grout, if your application requires it. This is important because, if you don’t, the grout will absorb into your stone just like the sealer would have, and will stain your stone. Furthermore, if you apply sealer to your grout there will be no way for any water that does get behind your newly waterproofed stone to escape, and it will be easier for mildew and mold to grow behind it.

When it comes to the actual application of the sealer, the first step is to clean your stone completely. Use a stone cleaner and a soft cloth to buff them clean, and let the product dry completely. If the stone has darkened during the cleaning process, wait until it returns to its original colour before attempting to seal it, to let the water evaporate completely from within the stone.

Next, pour the stone sealer into a bowl large enough to dip a foam paint brush into, and open a window and/or turn on a fan, because many sealers contain strong fumes. If you are planning to seal stone outdoors, plan to do so when you can guarantee that there will be no rain for the next 24 hours after the application.

Dip your foam paint brush into the sealer and apply it onto your stone in broad, overlapping strokes, working from top to bottom if your stone is applied vertically, to prevent drips, or working in small sections at a time if the application is large enough to require it. The most important thing is to avoid streaks, and to apply the sealer evenly. 

Leave the sealer to absorb as long as the instructions require. Most sealers specify 10 minutes. After the sealer has been absorbed into the stone, use a clean cloth to buff the stone and remove any sealer that hasn’t been absorbed. Use a circular motion, beginning with the stone you sealed first, and clean it until the stone is no longer tacky and the tiles are dry.

Particularly porous surfaces may require multiple applications. You can test your sealed stone to determine if it is completely sealed after 2 hours by applying a drop of water to the surface. If the water penetrates, an additional application is required. Consider trying this on your test stone prior to the full application. Your sealed stone will be ready for surface traffic after 2 hours, but should be kept dry for at least the first 12. It will be fully cured after 24 hours. 

And that’s it! You won’t need to reapply your sealer for a few years. All you need to do now is keep your stone clean like you normally would. The number of years between re-applications varies depending on the stone type, the sealer, and the amount of wear, but testing the quality of your sealer is easy. The same drop of water test that is used to determine whether a second coat of sealer is necessary for your stone can be used to determine when your sealer has worn away enough to need a re-application.