Natural stone is a material that is quarried from the earth. There are a wide variety of types of natural stone that can be used in drink coasters. Caring for and maintaining these different types of stone requires different precautions based on the chemical makeup of the material being used. Not all stone is the same, and it is important to understand the exact nature of the type of stone used, in order to understand how to care for its natural properties.
The classic stone for beverage coasters is marble. Elegant, refined, and sophisticated, marble is a material that has graced the architectural and artistic masterpieces of the human species for centuries. When used in drink coasters the material is generally polished smooth, although it is possible to get them ina less slippery tumbled finish.
Caring for marble drink coasters is one of the most difficult types of stone to maintain. This is because marble is a solid base, in the acid base relationship. That means that if any acidic substance comes in contact with the marble, that a chemical reaction will occur, causing the stone to discolor. Luckily most marble coasters are treated with an invisible chemical sealant to prevent this, however that does not deny the fact that the sealant can wear down over time, leaving the coasters vulnerable.
The best way to wash marble coasters is to simply use a scratch free cloth, along with mild warm water. Do not use soap or other chemical cleansers as these are often acidic in nature. If you have a natural cleansing product that is not acidic, or a marble cleaning product, those can be used.
Slate is a much more rugged, more durable material, that is often used in beverage coaster manufacturing. In general, slate wont need much maintenance. Unlike marble, slate does not react quite as obviously as marble to acidic substance, although if something acidic does get on the coaster you should wipe it down immediately, as over time stains can form.
Sandstone is one of the most popular stone coaster materials available. It is highly absorbent, and so when you put a sweaty glass down on it, the moisture absorbs into the stone, remaining locked within the material until such time as it can be evaporated away into the air.
The only problem with sandstone is that it absorbs all moisture, not just condensation. That means that if a colorful fruit juice is spilled on the stone, the liquid will penetrate the surface of the material, and stain the stone from the inside, causing a mess that is almost impossible to remove.