For moisture and dust control on clay tennis courts, there's no better option than magnesium chloride or calcium chloride flakes. They absorb moisture from the air before clay court surfaces are overly affected by humidity. They also have anti-ice properties due to being types of salts, making them ideal for all climates. The presence of magnesium chloride and calcium chloride serves to increase water hardness, so they also reduce erosion. Both are 100% environmentally-friendly.