Expert: James Yee - 11/9/2007

Question
QUESTION: hi,
I live in Scotland, and it's quite chilly here at the moment. I keep my humidor in a room without central heating so the temperature does not vary too much. I am using a Xikar Crystal Humidifier (with PG and distilled water) and Xikar Digital Thermo-hygrometer, which has been calibrated and is accurate.

In my humidor the temperature is 61F and RH78%. Most of my small cigars seem OK, but the really big ones feel a bit crackly. I have read that it is not possible to have equivalent moisture in the air to equal 70/70 at 60F. What should I do? Every part of my house will be at this temperature for at least most of the day, and this temperature is likely to drop considerably over the next few months.



ANSWER: Hi Michael,

The humidity in your humidor MUST be between 69-73% humidity, regardless of humidor temperature.  Even though your cigars may appear fine at 78%, prolonged exposure to this much humidity can cause mold growth.  If the humidity is consistently at 78%, you may want to fine-tune the 50/50 PG solution by adding a few extra drops of PG (no more than 2-3 drops of PG).  This will lower the humidity closer to 70%.

In terms of temperature, if you can relocate your humidor to a warmer room, the humidity in your humidor will be more effective for your cigars.  At colder temperatures, humidity in your humidor is less effective and harder to maintain so it’s important that the humidor temperature is also in a reasonable range (68-74 degrees Fahrenheit is the safe range) for your cigars.  If possible, try moving your humidor to a room with an ambient temperature between 64-70 degrees Fahrenheit and that should boost your humidor’s internal temperature to a reasonable level.

Keeping your humidor near a natural light source (such as a window) during the day should slightly increase the humidor’s temperature to a more reasonable level.  Do not let the humidor sit in direct sunlight but instead, nearby and close enough to slightly feel the warmth of sunlight.  Placing your humidor near a window in direct sunlight can raise the temperature as high as 80 degrees, which is not good.  

Hope this answers your question. If you have any more questions, please feel free to just ask and I’ll be happy to help.

Regards,
James


---------- FOLLOW-UP ----------

QUESTION: thanks for your quick response.
although humidity is 78 my cigars are actually a bit DRY! here is a different answer I found for this problem

"Although humidity levels are almost always referred in terms of Relative Humidity, the actual value that is important is the amount of water vapor present in a given volume of air, known as Absolute Humidity. As air will hold varying amounts of water vapor at different temperatures, no discussion
of humidification would be complete without a discussion of temperature and it's effect on absolute humidity. Relative humidity is an easily measured value that relates the measured humidity to the maximum humidity that is possible at that temperature. Thus, 70% RH at 70 ºF is not the same as 70% RH at 80 ºF.

We are aiming to maintain the same amount of water (mgm/liter) around our cigars as seen at 70% RH at 70 degrees F (which is 13.15 mmHg water vapor pressure).

So, to be able to know what is happening with our cigars at temperatures other than 70 degrees F, we must use a table of adjusted relative humidity values to make sure that our humidors keep our cigars in the peak of condition.


Temperature, water vapor pressure and relative humidity required to equal 70% RH at 70 degrees (13.15mmHg).
    

Temp
  

Water Vapor Pressure
  

Relative Humidity
    

66
  

16.37
  

80.33%
    

67
  

16.95
  

77.58%
    

68
  

17.55
  

74.93%
    

69
  

18.17
  

72.37%
    

70
  

18.79
  

70.00%
    

71
  

19.45
  

67.61%
    

72
  

20.11
  

65.39%
    

73
  

20.81
  

63.19%
    

74
  

21.51
  

61.13%
    

75
  

22.25
  

59.10%
    

76
  

23.00
  

57.17%

It is not possible to attain an absolute humidity level that will keep cigars from drying out at temperatures below 60 degrees F. This observation will put to rest the fallacy that the refrigerator is a good place to store cigars. Not only do we have to worry about our premium cigars beginning to acquire the flavors from left over foods but the cigars will dry out and become essentially unsmokable. The freezer is an even worse place to store cigars. The humidity becomes virtually zero, and the loss of moisture from cigars will accelerate to produce a bone-dry smoke."

Im a bit confused...

ANSWER: Michael,

Here’s an excerpt from ASC cigar group’s FAQ that explains how low temperature should not be compensated by high humidity:

“The "Variable Humidity Myth...

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. Moisture content is NOT why we keep cigars at 70% humidity...

Here's a more scientific explanation debunking the myth of varying humidity from David E. Patton, Ph.D. at the Department of Physiology, UCLA School of Medicine...

"There has been extensive discussion on A.S.C. concerning the effects of temperature on humidity and its application to proper cigar storage. Much of the confusion concerning these concepts comes from not understanding what is happening at the molecular level.  My goal is to explain some of the revalent concepts and then to put the concepts together in such a way as to give an intuitive understanding of how they relate to cigar storage.
    
Cigars are made from tobacco leaves.  Tobacco leaves (like most plant material) consist primarily of carbohydrates and proteins.  Protein and carbohydrate molecules contain many binding sites for water molecules.  A certain proportion of the water binding sites need to be occupied by water molecules in order for the tobacco leaves to be adequately pliable, to burn properly and to age properly.  So when we think about humidity as it relates to cigar storage, the most revalent factor to consider is: are the correct proportion of water binding sites occupied?  Water molecules bind to other molecules via hydrogen bonds. Van der Waals interactions also participate. This applies to water bound to protein and carbohydrate molecules (e.g. tobacco leaves) or to other water molecules (e.g. liquid water). For the purposes of this discussion, water bound to tobacco leaves will be treated like liquid water.

Temperature is the main factor determining whether a water molecule will be more likely to be in either the gas or liquid (or bound) phases. This is because at higher temperatures, water molecules (like any other molecule) will have more kinetic energy.  The more kinetic energy a molecule has, the higher its probability of being in the gas phase.  This is because it will have sufficient kinetic energy to  break out  of the hydrogen bonds and Van der Waals interactions that would otherwise keep it bound. At lower temperatures molecules have less kinetic energy so when they collide with a carbohydrate molecule, for example, its kinetic energy is insuficient to break away from it. The important point here is that at higher temperatures, a water molecule is more likely to be in the gas phase and less likely to be bound.  At lower temperatures a water molecule is more likely to be bound and less likely to be in the gas phase.

Another point that needs to be explained here is the concept of relative humidity.  Simply stated, relative humidity is the ratio of the concentration of water in the gas phase divided by the maximal concentration of water the air can hold (the saturating concentration) at a given temperature.  Air holds more water at higher temperatures.  Therefore, if you hold the relative humidity constant and increase the temperature, the concentration of water molecules in the gas phase will increase.  If you think about this superficially you may think that because the concentration of water molecules increases in the gas phase as you increase the temperature (holding relative humidity constant)that your cigars will become over-humidified.  This is WRONG.  Remember, as you increase the temperature, the water molecules are less likely to be bound to the tobacco and more likely to be in the gas phase.  Thus, to keep the same proportion of water binding sites in the tobacco occupied by water molecules, the concentration of water molecules in the gas phase must be increased when temperature is increased.

Again, cigars should be stored at 70 - 73% relative humidity, regardless of temperature. Period.”


---------- FOLLOW-UP ----------

QUESTION: thanks again, this is excellent information, particularly with all the conflicting info onthe web.

BUT... any suggestions why my cigars are brittle despite being overly humidified?

Answer
Hi Michael,

It may be possible that your larger cigars (the brittle ones) are not receiving enough humidity; especially if you have a large humidor and a large collection of cigars where they can be obstructed by other cigars.  Try rotating your cigars periodically - maybe once every 1 to 2 weeks  - and allow the larger cigars more exposure to humidity.  If you've added the larger cigars recently, allow them more time to adjust to the humidity.  If the cigars are in cigar tubes or plastic wrappers, remove the caps from the cigar tubes and untuck the opened ends of the wrappers so that more humidity can pass through.

Also, make sure that the humidification device is not placed directly next to the hygrometer or facing it in close proximity.  Some digital hygrometers can be extremely sensitive and give off false/incorrect readings when it is placed directly next to a strong humidity source.

Hope this answers your questions.

Regards,
James