Memory foam can take quite a while to dry—anywhere between 10 and 24 hours—because it’s such dense material. The thicker the topper, the longer it will take to dry. It’s important though, to let your mattress topper dry completely before re-covering it or placing it back on your bed. If you replace it while it’s still damp or wet, the moisture can lead to mold and mildew. The best way to dry your topper is to let it air dry somewhere with good airflow. Avoid placing it in direct sunlight which can damage the topper. You can also use a hairdryer at a distance with settings on low. High heat can damage the memory foam’s cells and structure. Wringing, squeezing, or tumble drying it in a dryer will also ruin the topper and you should never do this.