All natural stone is porous because of the sheer number of capillary pores that liquids and gases can move around. There are many types of natural stone, such as; sandstone, limestone, marble, travertine, slate, granite and basalt; all have porous materials that act like hard sponges, and soak up liquids, dissolved salts and minerals over a long period of time.
Sandstone is considered a very porous stone as it absorbs liquids fairly quickly, whilst the more dense igneous stones like granite are much less porous and can take an hour or more to absorb water-based liquids and oils.
Natural stones like Sandstone, Limestone and Marble are used in a variety of places around the home, as well as in public areas. Because stone has excellent durability, strength, insulation properties it has been a popular material for building and decorating since ancient times.
Although the variety of colours, and types of stone make it a truly versatile landscaping and building material, you must seal this type of stone to prevent damage from staining.
Back in the ancient Roman times, Natural Stone Sealer Sandstone and natural stone were sealed with Olive Oil which provided some protection against general weathering from the elements. Later, during the Renaissance period, Europeans decided to use topical sealers and varnishes made from egg whites and natural resins. These were clear in colour and when applied wet they formed a protective layer and hardened the stone.
Nowadays, modern stone sealers are split into the following three types; Topical sealers, Impregnating sealers and Penetrating sealers.
A topical sealer is effective at preventing stains but as it is exposed on the surface of the material it can tend to wear out fairly quickly, more so if the flooring is used frequently. The slip resistance and look of the stone will change significantly, especially when it is wet.
Topical sealers do not allow the escape of gasesor water vapour, so they will not be effective against salt crystallising on the surface.
Topical Sealers are generally made from polyurethanes or acrylics.
Penetrating sealers are breathable to a certain extent, but can only penetrate to just under 1mm
into the surface of the stone – just enough to secure the material to the surface. Generally this type of sealer lasts longer than the topical sealer, but they do not change the appearance of the stone, and the slip resistance on the stone surface can wear fairly quickly. This type of sealer is not suitable for preventing salt crystallising on the surface.
Special cleaners are often used alongside the penetrating sealers to clean and top up any repellent ingredients left on the surface of the stone.
Most penetrating sealers use siliconates, fluoropolymers and siloxanes.
Impregnating sealers are a type of penetrating sealer which infiltrates deep into the stone, and soaks it with the molecules that bond with the capillary pores. It then repels water and oils from within the material. Some silane sealers have been modified to impregnate deeper into the stone which protects against salt crystallising on the stone surface, as well as providing crucial protection from traffic and weathering.