Xikar’s Propylene Glycol (PG Solution) maintains 70% RH. Distilled water evaporates quickly and creates humidification fluctuations. Xikar's proprietary mix of PG Solution is calculated to match the water absorption rate with the rate at which PG biodegrades, resulting in a humidor that will not over saturate with PG. Always maintain 70% RH for the best results. Competitive mixtures of PG Solution often contain an incorrect mix resulting in a clogged humidifier.