Sandstone has a porous structure that naturally absorbs water, making it the perfect material for beverage coasters. Conversely, its absorbent surface also makes it a challenge to clean, as it quickly absorbs and sometimes retains spills. The final sandstone coaster product also poses additional challenges. Some sandstone coaster manufacturers cut or etch the sandstone with patterns that easily retain dust, dirt and other debris; paint the sandstone without a sealant leaving painted images exposed to moisture and wear; or back the coasters with felt, cork or tiny feet that can also retain debris and stain, tear or fall off.
Place under cold running water, if your coasters have cork, rubber or silicone backings or feet, to rinse away any dust or light dirt.
Wipe with a clean microfiber cloth or sponge, if they have felt backs, to rinse.
Remove dirt, dust or other debris from felt backings with a soft lint brush or tape-style lint remover roller.
Set your coasters aside to air dry.
Wash your coaster(s) with a small amount of mild soap/detergent and water if coated in a sticky beverage or stained. Although fresh spills can come out of sandstone easily with plain water, using mild soap guarantees that you have completely removed any sugar that could attract insects.
Gently scrub any tough stains, or dirt, food or other debris lodged in any etched artwork or cracks in the sandstone, with a soft-bristled brush.
Remove any remaining soap residue by rinsing your coasters for at least five minutes under running water.
Air dry your coasters.
If a sandstone coaster stops absorbing water, the pores of the stone have likely clogged. Dry-dust your coasters at least once a week and immediately clean spills to prevent this from happening. If your coaster does get clogged, wash it with a mild dish detergent and a brush to break up any dust and dirt that may have combined with natural oils from your skin or other debris. Rinse with clean running water and air dry (at least overnight). If you have a fresh ink stain on a sandstone coaster, blot immediately with a paper towel, apply a small amount of hydrogen peroxide to the stone to break up the ink, wash the area, rinse and air dry.
Always use a microfiber cloth, sponge or other non-textured cloth when wiping sandstone as textured cloth can catch on the sandstone leaving behind textured materials such as lint, fibres or thread. Don't scrub any images printed on your sandstone coasters as you can rub them off unless the coaster manufacturer pretreated/sealed the image. Never place sandstone coasters in a dishwasher as the heat can not only damage or break down cork and felt backings, but can also melt the adhesives that hold the backings or feet to your coasters. Never use undiluted bleach on your sandstone coasters to remove germs or kill bacteria as the bleach can damage/break down the porous stone and destroy cork or felt backings--a mild detergent can provide enough cleaning power.