Topical sealers are some of the most commonly available on the market today, and can be used in a wide variety of interior installations. They are generally only used for polished marble installations, given that they work by adding a layer of sealant on the surface of the marble that acts as a protective layer.
This layer, while adding protection, also creates a glossy finish that works well with already polished marble surfaces. Unfortunately, it tends to wear off fairly quickly, so if you use a topical sealant in a heavy-traffic area you will need to reapply the sealant periodically throughout the year.
They are readily available at your local home improvement store.
Penetrating sealers are used more frequently than any other type. They work well in both interior and exterior applications, and rather than forming a protective barrier on the surface actually penetrate into the stone to create a barrier that repels moisture from the surface.
It also allows the stone to retain its natural look. Penetrating sealers are commonly used in areas such as entryways, kitchen countertops, bathroom floors, or backsplashes.
They usually need to be applied every six months or so to protect against moisture, and can be used in both interior and exterior installations. Like topical sealers, they can be purchased at your local home improvement store.
Impregnating sealers are the most durable sealers available, and are used in areas where heavy traffic and moisture are prevalent, such as exterior walkways, showers, bathtub surrounds and steam showers. They penetrate into the stone itself and actually bond with the elements within the stone, repelling not only water but mineral absorption as well.
Similar to penetrating sealers, impregnating sealers do not affect the color of the marble, and can usually be applied once a year, although every six months is recommended for areas where traffic or moisture is prevalent. These are the most expensive sealers available, and while they can occasionally be purchased at your local home improvement store, they might only be available from a flooring store, depending on where you live.