How Sealers Work

• The primary purpose of sealers is to protect the natural stone from staining over time. Since slate is naturally porous, it will retain any moisture that it comes into contact with, eventually soaking up the minerals in water and dyes in other liquids. Sealers work by either creating a protective barrier on the surface of the stone itself, or by penetrating into the stone and creating a barrier that repels moisture over time. The secondary purpose of sealers is to protect the installation itself, because water damage can harm the thinset beneath the slate as well as the substrate beneath..
  
  

Types of Sealers

• Three primary types of sealers are made--topical, penetrating and impregnating. Each type has its own strengths; deciding which one to use is entirely up to personal preference.
  
  Topical sealers create a barrier on the surface of the slate or natural stone. Since they act as a barrier on the surface, they generally create a glossy, polished sheen on the surface. If you are looking to retain the natural look of the stone, you will want to avoid using topical sealers. They are primarily used for interior installations where an individual is going for a polished sheen on the surface but can be used in wet and dry areas.
  
  Penetrating sealers actually work their way into the stone itself, and create a protective barrier just beneath the surface, thus preserving the natural look of the slate. These are the preferred types of sealers used with natural stones--particularly slate--and are used primarily for interior installations outside of wet areas.
  
  Impregnating sealers are generally reserved for exterior installations or installations in wet areas, such as showers, bathrooms, kitchen countertops and backsplashes. They work by penetrating deeply into the stone and creating a bond within the stone itself that not only repels moisture but also protects against mineral buildup.
  
  

Seal the Slate

• You can seal your slate installation in several ways. First, you can simply use a paint brush if you are working with a small enough area. The stone will soak up any excess sealer that is left on the surface, so you do not have to worry about applying an absolutely even coat. Every type of sealer requires additional applications over time to protect the stone and installation fully. Usually, this should take place once or twice a year.
  
  In addition, sealer can also be applied in spray-on format, either through the use of pre-packaged spray bottles or by purchasing a commercial sprayer or pump sprayer as used when spraying for weeds in gardens. Sprayers are usually reserved for large areas where spray bottles or paint brush applications are too small.
  
  Always wear safety glasses, a respirator mask and gloves when working with sealers or chemicals of any kind. Open any doors or windows for additional ventilation if you are sealing an interior area. Be sure to read the label on your sealer container for the precise drying times, as well as recommended re-application times. All your supplies can be purchased at your local home improvement store.