Going Green: Using a Limestone Sealer

Wondering why you should use a limestone sealer for more eco-friendliness? Well, natural stones like limestone are porous and easily absorb oils and water-based liquids, which stain and mar the longevity of a product. To prevent the stone surface from retard staining, sealers are applied. Staining, salt spalling and efflorescence; acid attacks from food and “frame” effect are the most common damages that occur if the surface is not sealed. The ancient Romans used olive oil to seal their stone, it provided some protection against the ingress of water and general weathering, but stained the stone permanently. The Europeans during the Renaissance used topical varnishes and sealers manufactured from egg white and natural resins and silica. These could be applied wet and upon drying formed a hardened protective skin.

Limestone absorbs these products deeply into its capillaries, where it is impossible to reach and remove; thus affecting the luster, longevity and performance of the stone. To protect limestone from damage and improve its longevity and increase its usefulness there are primarily 3 types of modern sealants available: topical, impregnating and penetrating sealers.

Modern Sealers

Topical sealers: Made from polyurethanes or acrylics, this limestone sealer is effective at arresting stains; however, applied on the stone surface tend to wear out quickly. Additionally, these sealers are ineffective against salt attack that includes efflorescence and spalling. Since it does not allow the escape of water vapur and other gases, it sure changes the lustrous look of the stone and makes the surface less slip resistance, especially when wet.

Penetrating sealers: It is manufactured from liquid repellents like fluoro-polymers, siliconates and siloxanes. It penetrates the stone surface deeply and anchors the material to the surface strongly. Penetrating sealer is long-lasting than topical sealers and alters the anti-slip characteristics of the surface. It requires special cleaners to clean and top up the repellent ingredients on the stone surface. Even though this sealer is breathable to an extent, yet it is not effective against salt attacks.

Impregnating sealers: Silanes or modified silanes are used to create this type of modern sealer. A step further ahead than the penetrating sealer; impregnating sealer penetrates deeply into the stone bonding the capillary pores and repelling water and oils from within the material. Some modified silane sealers provide protection against efflorescence, spalling and picture framing. Other impregnating sealers offer protection against weathering.

Sealing Limestone

Limestone being soft and porous is sensitive to acidic attacks and can be easily destroyed upon contact with acidic products. Therefore, it must be sealed to provide adequate protection against damage and improve its shelf-life.

The Sealing Process of Limestone

It involves the application of sealant on a completely dried stone surface. The stone surface must be vacuumed and wiped dry with a tack cloth to erase the slightest sign of dirt and dust. Prior to application the surface must be subjected to drying for up to 72 hours, and covered with mask tape to avoid the sealer’s penetration.

Pour limestone sealer into a shallow pan, and evenly paint the countertop with liberal amount of sealer. Allow it to penetrate the limestone surface for an hour before applying the second coat. The limestone sealer would last up to 5 years if properly applied.