Because they have plenty of crevices where food particles can collect and fibers in which mold can grow, bamboo placemats need frequent cleaning. You can't just toss one in the washing machine, though, nor should you immerse it in water for any length of time. The fibers in bamboo swell when they absorb moisture, and the mat can literally get bent out of shape. Frequent wiping with a damp rag is preferable to immersion, and when it comes to controlling mold, consider using vinegar. It kills over 80 percent of mold while being 100 percent safe to use.
Shake down each of your bamboo placemats over the sink at the end of each meal. This is the best way to ensure that food particles don't lodge between the strands and create oily stains.
Mix a mild detergent solution by putting a capful of dish soap in a gallon of warm water. Soak a sponge in the solution and wring it out thoroughly before wiping down both sides of the placemat.
Dry the mat thoroughly with a clean rag after washing it to prevent moisture from swelling the bamboo fibers.
Spray both sides of each mat periodically with full-strength white vinegar. Scrub the vinegar into the crevices between slats and around the fringes of the mat, using a toothbrush. Wipe it off with a sponge dampened with clean water, and then dry the place mat with a clean rag.
Remove juice and food stains with a solvent. Try spot cleaning the stain with a rag dampened with rubbing alcohol.
Freshen up the shine by rubbing on a light layer of mineral oil. Don't use any type of non-food-safe wood refinishing oil, such as linseed or tung oil.