Expert: James Yee - 9/28/2009

Question
I have seen in numerous posts on here discussions about how to store cigars.  While I find your posts informative and engaging, I am confused by the topic of absolute vs. relative humidity.  Frequently in your recent posts you have stated that relative humidity should be adjusted for temperature, that is at lower temperatures the relative humidity needs to be increased to maintain the same absolute humidity.  However in your reply to a reader question dated 11.9.2007 you quoted an excerpt from a UCLA professor (derived from Cigar FAQ I believe) debunking the myth of variable relative humidity based on temperature.  That is that relative humidity should be kept constant regardless of temperature and that storage based on absolute humidity is erroneous.  I have seen some reputable cigar manufacturers list the table of relative humidity vs temperature but have also seen numerous data debunking the absolute humidity theory.  The debate is even present on your own site!  A post answered by Bill Finck Jr. on 9.21.2009 recommends to the reader to adjust his humidity based on temperature!  Please help clear up this question to a budding cigar aficionado.

Answer
Hi Mike,

For decades, the idea of compensating low temperatures with more humidity has been discussed and debated thousands of times among cigar smokers.  I think ASC best answers this in their FAQ:

From ASC's Cigar FAQ:

"Many self-proclaimed "authorities" have been making a serious mistake of confusing moisture content with relative humidity lately. At least one well-known Cigar distributor has added strength to this legend by distributing a table recommending different relative humidities at different temperatures. Don't fall for this "urban legend"! Cigars should be kept at 70% RH REGARDLESS of temperature or you WILL ruin them...

The modern myth of varying humidity with temperature is based on an entirely false premise. Cigars don't care about absolute moisture content. They need just enough moisture to keep the tobacco pliable, but not so much to swell it. This occurs at 70-73% REGARDLESS of  temperature.

Tobacco should be kept at a relative humidity which just keeps the leaves pliable without swelling them. Since that pliability is based on the interaction of the cellular membranes with the air surrounding them, *relative humidity*, not absolute moisture content is what's important. This isn't chemistry, it's mechanics - on a cellular level. Ideally, the correct point is 70-73% regardless of temperature. At 70% relative humidity (a measure which by definition is independent of temperature) cigar leaves become pliable without swelling. at 75% or higher, the cells begin to swell. at 68% or lower, they can become brittle. These points are regardless of the ambient temperature or the absolute moisture content.

Does it make any sense to a rational person to keep their cigars at close to 100% humidity at 60 degrees? Anyone living in cold climates can attest to the fact that at 60 deg, their cigars are perfect at 70%, and (as they would at any temperature) their cigars are prone to mold and swelling at humidities above 80%. Those living in the tropics will tell you the same thing - their cigars MUST be kept at 70% humidity at storage temperatures of 80 degrees. According to "the table", those cigars should be at 50% humidity? I'll tell you what... If the humidity drops below 68%, your cigars will become dry and crack - I couldn't even imagine how badly dried out they'd be at 50%!

Try it yourself. The "logic" of varying RH with temp falls apart in the real world."

While the theory of compensating temperature with humidity sounds plausible (even I was taught this when I first started smoking cigars), I believe ASC's explanation is correct.  Unfortunately, this issue is still on-going with many cigar smokers.  (Perhaps the folks at Mythbusters can settle this for us?)

Regards,
James