Any tonewood may warp or rupture when dry. The ideal humidity for ukuleles is therefore 40 to 60 percent. In cold climates, this value can easily be undershot if the room temperature drops and the air can therefore absorb less moisture, or if room heating removes moisture from the air. To avoid this, humidifiers should be used. They are usually hooked into the device through the sound hole and in a controlled manner release moisture into the interior of the body.


Paul Marchese: DIY Instrument Humidifiers for your classroom! (2018)

Oasis Ukulele Humidifier

Oasis manufactures humidifiers specifically for ukuleles. They consist of a tube of moisture-permeable textile fiber in which moisture-binding (hygroscopic) crystals of humigel are located. The tube is filled with distilled water with a supplied syringe. Humigel ensures that the water becomes semi-liquid in a short time. This protects the ukulele from leaking water and provides a controlled, long-lasting release of moisture. However, Humigel must be replaced from time to time if it has lost its moisture-binding effect. Distilled water must be refilled approximately every 7 to 10 days.