As long as we're on the subject about humidity control....
I don't know if this has been posted on any of the myriad of threads on the beads/humidity subject before but I found it interesting.
C&P from Smoke Shop Magazine:
As an article in Smokeshop ("Fresh Cigars Keep Sales Fresh," April, 1999) pointed out, cigars react indignantly to alternate drying and humidifying. They pout in a sense, at least at the foot, where they swell and split. In that story, Howard Ingber, a chemical engineer and creator of Cigar Oasis electronic humidification devices, contributed much to the knowledge of what happens when a cigar dries down or is rehumidified. Prior to his breakthrough research, the industry knew little about the process. How did moisture escape and enter a cigar? Did moisture pass uniformly through the wrapper, or via the open foot? Why did otherwise intact cigars swell and crack at the foot? Most importantly, how could tobacconists prevent the loss of expensive inventory this caused?
Ingber, whose work benefited the industry, experimented with drying down cigars from 70% relative humidity to 55% RH, and humidifying them from 55% to 70%. The results settled the debate as to whether the moisture entered or exited through the wrapper from head to foot, or only from the open foot. Well, sort of. Both occur, depending on the relative humidity in the room and inside the cigar itself, if the two differ. During dry-down from 70% RH to about 65% RH, moisture exits the open foot exclusively, and the wrapper is impervious to the transfer of the moisture in this humidity range. It does so in a matter of minutes, to boot. As the cigar's humidity drops below 65%, the wrapper leaf becomes porous, allowing moisture to escape right through the leaf. The cigar then dries down more slowly, until it reaches the relative humidity level of the surrounding air - 55% in Ingber's experiments.
The problem was much worse when Ingber humidified a dry cigar from 55% RH to 70% RH. Up to 65% RH, the process is reversed, with moisture entering the cigar uniformly along its wrapper's length. But above 65%, the wrapper loses its permeability and acts as a barrier to the transfer of more moisture. Only the open foot allows the entry of humidity, and a severe humidity gradient between moist foot and dry head occurs. Disaster! The humidified foot swells more than the rest of the cigar ... as the foot swells, the wrapper splits in that area.