How exactly does the use of Propylene Glycol (mixed with distilled water) aid in the humidification of cigars?
Any solution with a fixed composition has a fixed vapor pressure at a given temperature and total pressure. If the solution has only one volatile component (water), then the vapor pressure is caused by that component only (i.e., you won’t find PG in the vapor phase). By coincidence, the vapor pressure over a mixture of PG and water is about 70%. To put it more simply, PG is a hygroscopic substance – It absorbs moisture from the environment (like a salt shaker does in humid weather). The distilled water evaporates until the ambient humidity approaches 70%. At that point the PG won’t allow any more moisture in the air. Conversely, if there is too much moisture in the air, the PG solution absorbs the excess, bringing the system down to 70% as well. PG is certainly not the only solution which will regulate humidity properly for cigar storage. As several posters have pointed out, a glycerin solution will also work in a credo. Being a thicker substance, I feel that glycerin solutions ultimat
