The humidity controller absorbs excess humidity and releases it when sinking. This creates an even climate in the instrument. Please check the humidity again and again. Only moisten the humidifier at low humidity. Optimum humidity for pianos/grand pianos is approx. 40% Zum befeuchten des Stabes empfehlen wir unseren "Füllbeutel " einzeln oder im Set. Mould is caused by calcareous water. To avoid this, it is important to fill the humidifier with distilled water.