Humidity and Temperature relation

[mcease022]

Hi All,

I am trying to understand the relation between temp. and humidity. I have a tower humidor that I am trying to regulate. The bottom is at a higher humidity level (70%) than the top (65%). The temperatures are 72 on the top and 67 at the bottom. These numbers change a bit so dont take them at face value but the point is that the bottom is more humid and has a lower temp.

My question is does the bottom humidity level really equate to 70% given the temperature? I heard that 70% at 50 degrees is different than 70% at 70 degrees. Im just trying to understand.

If I am way off base and dont make sense let me know

Thanks.

[Kurt]

I've got the humidification unit mounted in the top and Xikar wireless one in the top and one in the bottom and I am experiencing the exact same phenomenon. Just for some sanity I have purchased the iCelcius unit with extended probe and will be monitoring from the middle.

My humidor is about 1 meter high and holds around 1000 sticks.

Kurt

[Fugu]

Hi All,

I am trying to understand the relation between temp. and humidity. I have a tower humidor that I am trying to regulate. The bottom is at a higher humidity level (70%) than the top (65%). The temperatures are 72 on the top and 67 at the bottom. These numbers change a bit so dont take them at face value but the point is that the bottom is more humid and has a lower temp.

My question is does the bottom humidity level really equate to 70% given the temperature? I heard that 70% at 50 degrees is different than 70% at 70 degrees. Im just trying to understand.

If I am way off base and dont make sense let me know

Thanks.

Hi,

You might have a look for the discussion in this thread. Same basic problem.

Please keep in mind that you are measuring relative humidity (Edit: so the answer is yes, bottom rH being indeed 70% given your instrument is reading +/-correct). The absolute humidity between bottom and top is about 1 gram per m³ different acc to your figures, with the top holding appr. 13 g water per cbm, the bottom ca 12 g/cbm. Ventilation might need some tweaking.

[Fugu]

Yes, because of the temperature difference the RELATIVE humidity is higher where the temperature is lower...bottom of the humidor. The ACTUAL amount of humidity suspended in the air is higher in the top of your humidor however. This is because warmer air is able to hold more moisture.

This general explanation is correct

I keep the cigars that require higher moisture content in the top of the cabinet.

This is not necessarily correct and depends much on the actual figures of temp and rH. Equilibrium moisture content will depend on relative and much less so on absolute humidity. With a certain influence of temperature as well, on which we are in the middle of a debate in another thread (with PigFish).

So, one needs to be very careful with such generalisations. In the case of the above figures with higher rH and lower temps at the bottom, the bottom cigars will likely be the ones with higher moisture content (despite the abs. water content of the air being about 8-9 % lower).

[garbandz]

got fans?

[PigFish]

There is no line that can be drawn that will define what rH means to cigar storage. Here are some guidelines.

As rH goes up, PMC (percent moisture content) of the cigar goes up

As Temp goes up, the PMC of a cigar goes down.

You must view water vapor bonding in a cigar is a tug-of-war with waters want to be free, or bonded to another substrate. That is all that there is to understand.

What rH is not. 100rH does not equal liquid water... 100rH means that 'space' is saturated with water vapor and that water will coalesce and condense somewhere to prevent over saturation. Just so you understand, 70rH does not mean that 70% of your cigar is water!

There is no direct correlation that can be read from any rH number to determine PMC in a cigar. I just does not work that way!

rH is a means to determine with an instrument how much water vapor is suspended in space. It has a partner and that is temperature. rH data, without temperature data is useless! It is useless in a pshychromatic table as it is in PMC measurement in a cigar. rH can tell you if you will be uncomfortable in a long sleeve shirt! rH represents a general comfort and discomfort range for humans. It also helps environmental controls folks understand the energy, and the energy to heat air to make humans more comfortable.

If you want to know how much water vapor exists in space, it can be determined with a psychromatic chart, table or calculator. Before you get all wet over the idea, you should understand that there is no line on the table that shows you the PMC of you cigars. As a matter of fact, most that enter the realm of absolute humidity aH get more confused than before because now they worry about yet another number that has little to show you about the condition of a cigar, that rH and temperature could not tell you without the calculation!

If you want to get your head around rH, then read about it. Learn that it is simply a definition... It is a ratio of vapor pressures. That is what it is!

If you have specific questions, if I can answer them directly I will try. This is the best I can do on the fly... telling you what rH is not!

Cheers! -Piggy

[TypicalSituation]

I was always under the impression rh went up as temp went up (in a sealed environment like a humidor) . I sit at 60 rh at 67 degrees, and 61 at 68 degrees. 63 at 69 degrees. This is a constant up and down in my humidor.

[PapaDisco]

I was always under the impression rh went up as temp went up (in a sealed environment like a humidor) . I sit at 60 rh at 67 degrees, and 61 at 68 degrees. 63 at 69 degrees. This is a constant up and down in my humidor.

There's a difference between humidity and relative humidity. The relative part is relative to dew point so as temperature increases rH tends to decrease as you get further away from dew point; all other things (available water) remaining unchanged. Your intuition that a higher temperature can support more moisture in the air is correct, but the thing our hygrometers are measuring is rH which is relative to dew point.

[luv2fly]

Get this question a lot here as it relates to mold growth on the floor joists in a crawl space.

The outside air is 90* and the RH is 70%.

When this parcel of air enters the crawl space, it is much cooler in the crawl space. The temp drops and the RH increases. Not adding any moisture to the air.

Colder air cannot hold as much moisture as warmer air so the RH increases. If the dew point is met, condensation can form. I have seen it dripping off of duct work (which is very cold) and if I touch the subfloor insulation it "rains" on me.

Same thing happens when one is outside on a hot summer day with a cold glass of whatever. The glass sweats. The liquid in the glass is cooling the glass which cools the air adjacent to it. It lowers the air temp to the dew point and the condensation forms on the glass.

Same reason there is dew or frost on the grass in the morning although this has to do with radiation cooling.

May be repeating what Piggy and Papa said but I love this stuff. Just remember this from my aviation weather days.

JMHO.

[PigFish]

Get this question a lot here as it relates to mold growth on the floor joists in a crawl space.

The outside air is 90* and the RH is 70%.

When this parcel of air enters the crawl space, it is much cooler in the crawl space. The temp drops and the RH increases. Not adding any moisture to the air.

Colder air cannot hold as much moisture as warmer air so the RH increases. If the dew point is met, condensation can form. I have seen it dripping off of duct work (which is very cold) and if I touch the subfloor insulation it "rains" on me.

Same thing happens when one is outside on a hot summer day with a cold glass of whatever. The glass sweats. The liquid in the glass is cooling the glass which cools the air adjacent to it. It lowers the air temp to the dew point and the condensation forms on the glass.

Same reason there is dew or frost on the grass in the morning although this has to do with radiation cooling.

May be repeating what Piggy and Papa said but I love this stuff. Just remember this from my aviation weather days.

JMHO.

Water exists in space without air! Water behaves the same without air. Take 'air' out of all of this and you are exactly right! It is all about water and heat. Heat changes the energy of water and when it runs out of 'steam' it coasts to a stop somewhere...

[PigFish]

Pigfish is much better equipped to explain the scientific reasons, but without extra circulation fans, the cigars in the top of my 6'6" cabinet are less dry than the ones in the bottom. It seems counterintuitive, but I can only go by my experience.

Posted a bunch of this on another thread(s) many of them.

Air is largely N(2) and O(2). H2O is just that. Check the molecular weight of the 3... The heaviest fall while the lights rise. H2O rises, in a mixture of gasses, largely weighing less [edit] than (dry) air!

-Piggy

[PigFish]

Guys, rH is a definition of a phenomenon. It is the saturation percentage of space at a given temperature. That is all that it is! We use it, with temperature, crudely, to attempt to estimate percent moisture content of a hygroscopic material.

-Piggy

[poorman]

If I keep my humidor at 65% year round, but temp ranges from 14c in winter to 18c in summer, at what time will they have more water content?

[luv2fly]

Local weather guy has had a hard time with snowfall prediction. Did an interesting thing today. Put 3 inches of snow in a cup and 5 inches in another cup. Let it melt. The difference in the liquid water in both glasses was barely undetectable. Not that it has anything to do with the topic but thought it interesting.

Amazing how little amount of water can increase the amount of snowfall.

[SCgarman]

It's funny all the discussion about technical jargon regarding storing our cigars, when in Cuba all they do is store the boxes in glass door cabinets or just out in the open in LCdH stores! Cuba is basically one big natural humidor for cigars. AFAIK, they use no humidification there. I'm sure if somebody who worked in a LCdH in Havana read these type of threads, he would not know what to think!!

[luv2fly]

Bottom line is that my cigars smoke wonderful with my storage situation. All I can ask or hope for. IMHO.

[Fugu]

Pigfish is much better equipped to explain the scientific reasons, but without extra circulation fans, the cigars in the top of my 6'6" cabinet are less dry than the ones in the bottom. It seems counterintuitive, but I can only go by my experience.

Posted a bunch of this on another thread(s) many of them.

Air is largely N(2) and O(2). H2O is just that. Check the molecular weight of the 3... The heaviest fall while the lights rise. H2O rises, in a mixture of gasses, largely weighing less [edit] than (dry) air!

-Piggy

Correct, but now you are going to confuse people completely, Ray....

This is true but only holding for gas volumes of the same temperature (I am aware, you will know your ideal gas laws, but as it goes without saying for you, you didn't mention it). It's a matter of density. Gas density will be affected by absolute moisture (or put more neutral: gas composition) and temperature (and pressure of course, but that we can assume to be constant between top and bottom...). And in most real-life humidors there is variation of both in the vertical. But since mostly the top part is higher in H_abs and in temp, the statement usually still holds.

However, this (and your answer, although being correct) has little to do with Hutch's observation, since this is mainly about rH. Hutch, it might well be different in your humidor, therfore perhaps your deviating observations. But for the very example given by the OP (and this is a rather typical setup), the top shelf cigars will be dryer than those from the bottom shelfs, although the absolute water content in the bottom air will be lower..

The core and "take home" message in Ray's above post are the following two sentences:

"As rH goes up, PMC (percent moisture content) of the cigar goes up

As Temp goes up, the PMC of a cigar goes down."

At 70% rH / 67°F bottom and

65% rH / 72° F top, you can easily deduct which is which with regard to tobacco moisture.

It's about the particular behaviour of a hygroscopic substrate, the equilibrium moisture content of tobacco, and not about the absolute water content of the surrounding atmosphere! (As Ray mentions with some regularity...)

I really recommend reading the post referred to in Post #3, where there is some in-depth examination of all that. I think we, and in particular Piggy, doesn't need to repeat that thread in full here again.

[PigFish]

Correct, but now you are going to confuse people completely, Ray....

This is true but only holding for gas volumes of the same temperature (I am aware, you will know your ideal gas laws, but as it goes without saying for you, you didn't mention it). It's a matter of density. Gas density will be affected by absolute moisture (or put more neutral: gas composition) and temperature (and pressure of course, but that we can assume to be constant between top and bottom...). And in most real-life humidors there is variation of both in the vertical. But since mostly the top part is higher in H_abs and in temp, the statement usually still holds.

However, this (and your answer, although being correct) has little to do with Hutch's observation, since this is mainly about rH. Hutch, it might well be different in your humidor, therfore perhaps your deviating observations. But for the very example given by the OP (and this is a rather typical setup), the top shelf cigars will be dryer than those from the bottom shelfs, although the absolute water content in the bottom air will be lower..

The core and "take home" message in Ray's above post are the following two sentences:

"As rH goes up, PMC (percent moisture content) of the cigar goes up

As Temp goes up, the PMC of a cigar goes down."

At 70% rH / 67°F bottom and

65% rH / 72° F top, you can easily deduct which is which with regard to tobacco moisture.

It's about the particular behaviour of a hygroscopic substrate, the equilibrium moisture content of tobacco, and not about the absolute water content of the surrounding atmosphere! (As Ray mentions with some regularity...)

I really recommend reading the post referred to in Post #3, where there is some in-depth examination of all that. I think we, and in particular Piggy, doesn't need to repeat that thread in full here again.

I try to keep it as simple as possible mate...! -LOL -Piggy

[PigFish]

Bottom line is that my cigars smoke wonderful with my storage situation. All I can ask or hope for. IMHO.

While Fugu and I get a little tangental in the Jolly Jump, this is really all that matters! While there are the rights and wrongs of the topic the bottom line is personal satisfaction with one's own smoking experience. There is no perfect humidor, nor perfect human or machine to monitor it. None of it needs to be perfect to get a perfect smoke in one's own world.

I enjoy the academic discussion for the most part, and I would like to think that I help more than I confuse but it is really all about simply smoking the best cigars you can, and making the most of those cigars buy storing them right and not allowing the weather and water content ruin your smoking experience!

Cheers! -Piggy

[Fugu]

While Fugu and I get a little tangental in the Jolly Jump, this is really all that matters! While there are the rights and wrongs of the topic the bottom line is personal satisfaction with one's own smoking experience.

Always right, but in our complacent self-reflection we should not forget the OP's original questions...

[PigFish]

Always right, but in our complacent self-reflection we should not forget the OP's original questions...

... and what was that again?

[mcease022]

If you want to get your head around rH, then read about it. Learn that it is simply a definition... It is a ratio of vapor pressures. That is what it is!

If you have specific questions, if I can answer them directly I will try. This is the best I can do on the fly... telling you what rH is not!

Thanks for the reply - I always enjoy reading your responses. I just skimmed your reply, and need some time to digest it. But, I have a question that I am not sure can be answered.

If at the top of my humidor the temp is 72 degrees and the humidity is at 65% and the temperature at the bottom is 67 - at what RH will the two be equal? if that makes sense?? If the two temps are different at what RH in each section will they equal since warm air holds more humidity. If this does not make sense at all please let me know.

garbandz

Yes I installed one fan for now at the bottom blowing air up. My humidification device is at the bottom. I will tinker with airflow in the cabinet and see what happens.

I dont want to obsess over this issue - although in time I might because I tend obsess over all of my hobbies. I will definitely try not to and just enjoy the smoking experience.

[CBMC]

If at the top of my humidor the temp is 72 degrees and the humidity is at 65% and the temperature at the bottom is 67 - at what RH will the two be equal? if that makes sense?? If the two temps are different at what RH in each section will they equal since warm air holds more humidity. If this does not make sense at all please let me know.

I doubt anyone will be able to give you an answer to that question. Tobacco retains more moisture at lower Temps. Pigfish has some charts from the cigarette industry that include moisture content in tobacco at different temps.

[Fugu]

... and what was that again?

[foursite12]

Quick Google search yields this for Havana rH. Blue line=average daily high, brown line average daily low.

"The relative humidity typically ranges from 50% (mildly humid) to 97% (very humid) over the course of the year, rarely dropping below 37% (comfortable) and reaching as high as 100% (very humid).

The air is driest around April 14, at which time the relative humidity drops below 57% (mildly humid) three days out of four; it is most humid around October 5, exceeding 94% (very humid) three days out of four."