65% Beads - 62F & 80%RH - Beads are Dry

[Scimmia]

I'd have to dig up some pages again, but as far as I can tell, there is always evaporation and condensation going on on the surface of water. The evaporation is a function of temperature, and the condensation is a function of vapor pressure. As temperature goes up, more water is evaporating, so you need a higher vapor pressure to maintain the moisture; and conversely, as temperature goes down, you need lower vapor pressure. Since relative humidity is a ratio of partial vapor pressure to saturation vapor pressure at a given temperature, relative humidity is the closest measure of net evaporation rates, and the amount of moisture in your cigars.

This is what I've been able to discern from various pages on the net, if someone has any additions/corrections, please speak up.

[RLembke]

That was all very well said...very concise. I like it....up until the last sentence. I agree RH is a ratio of the partial pressure of any gas to the saturation vapor pressure of just that gas in a closed system at that given temp. But does RH really give a measure of net evaporation? If RH gives an indication of a net evaporation, does that mean a closed system can never maintain an RH less than 100%? Does an RH of less than 100% mean water content is escaping our system? In the sense of a global system such as weather, that makes sense. If it's 70% RH, there is a net evaporation from our place of measurement to the greater environment. But for a closed system such as a humidor, there is ideally no net evaporation. I don't think RH is a measurement of net evaporation in our case. I think it is a measurement of the amount of water vapor in the air relative to what it can possibly hold.

As it relates to the amount of moisture in your cigars, assume when we put the cigars in the humidor that they have the ideal amount of water in them already. Now, what closed system conditions would that cigar need to see in order to keep the net evaporation from the cigar itself to be 0?

The thing I keep coming back to in my head is reading that no matter what the humidity is (AH or RH), you can never get enough moisture in air below 60F to keep a cigar properly moisturized (I need to find that link). Another example of that same statement is ice. Even when kept below freezing and in the solid state, ice will still evaporate (sublimate, actually) over time. The reason it is so slow is that the air temp has slowed the kinetic energy of the surface molecules. However, over time, the water molecules still want to go toward the area of less concentration and since air below 32F holds such little water vapor even at saturation, the ice will always evaporate. What makes a cigar at 60F any different than an ice cube at 30F?

The only problem are the conditions that begin to take place near saturation...mold, condensation, etc. If it was solely a question of maintaining humidity in a cigar, I think it's an AH issue.

[Scimmia]

Originally Posted by RLembke

That was all very well said...very concise. I like it....up until the last sentence. I agree RH is a ratio of the partial pressure of any gas to the saturation vapor pressure of just that gas in a closed system at that given temp. But does RH really give a measure of net evaporation? If RH gives an indication of a net evaporation, does that mean a closed system can never maintain an RH less than 100%?

Basically, yes, in a COMPLETELY sealed environment with freestanding water and nothing else to absorb it, the RH would be 100%. (or very close to it, in all practicality)

Does an RH of less than 100% mean water content is escaping our system?

No, it just means that the vapor pressure is enough that the excess vapor is absorbed (or adsorbed, in the case of silica gel) into something. It's an equilibrium, the rate of water evaporating should equal the amount condensing. In using beads or a credo, we can add or remove water vapor to help keep that equilibrium where we want it.

In the sense of a global system such as weather, that makes sense. If it's 70% RH, there is a net evaporation from our place of measurement to the greater environment. But for a closed system such as a humidor, there is ideally no net evaporation. I don't think RH is a measurement of net evaporation in our case. I think it is a measurement of the amount of water vapor in the air relative to what it can possibly hold.

Not really critical to our discussion, but air does not hold water vapor; water vapor is a gas on it's own, and exists completely independent of air. The only place air comes into this discussion is as it affects the temperature of the water.

As it relates to the amount of moisture in your cigars, assume when we put the cigars in the humidor that they have the ideal amount of water in them already. Now, what closed system conditions would that cigar need to see in order to keep the net evaporation from the cigar itself to be 0?

That depends on what that moisture content is. Remember, evaporation and condensation need to be at an equilibrium, so if the moisture content if the cigar is too high, it will give off more moisture than it receives because of vapor pressure at 65%RH, just as free standing water will give off more than it receives at a lower RH. (Hence the term used above, net evaporation. This may not have been the best term to use in a discussion not involving standing water.)

The thing I keep coming back to in my head is reading that no matter what the humidity is (AH or RH), you can never get enough moisture in air below 60F to keep a cigar properly moisturized (I need to find that link). Another example of that same statement is ice. Even when kept below freezing and in the solid state, ice will still evaporate (sublimate, actually) over time. The reason it is so slow is that the air temp has slowed the kinetic energy of the surface molecules. However, over time, the water molecules still want to go toward the area of less concentration and since air below 32F holds such little water vapor even at saturation, the ice will always evaporate. What makes a cigar at 60F any different than an ice cube at 30F?

True, the saturation vapor pressure at low temps is low, and as you said, so is the sublimation rate. Again, though, we generally have very low RH when we're talking about low temps. If you had a higher RH condition at these lower temps, it would have enough vapor pressure to force more of those molecules back onto the ice. Ice is closer to standing water, though, in that it would try to maintain 100% RH, so it is constantly loosing volume to sublimation, just as leaving a bowl of water out is constantly losing volume to evaporation. These cases are different than a substance that absorbs moisture.

The only problem are the conditions that begin to take place near saturation...mold, condensation, etc. If it was solely a question of maintaining humidity in a cigar, I think it's an AH issue.

Replies in bold.

[baglorious]

This thread has been very interesting, and I commend your level of investigation, research, and discussion. I wish I had time to get into it, but being an English major... my studies of physics relative to vapors was, well, uh... there weren't any.

I hate to take it back down to "dumb" level (for folks such as myself), and I hope this isn't entirely unhelpful, but as a "practical" matter, here are a few thoughts:

1. I believe there MUST be some abnormal condition in your setup of which you are not aware, whether it is something with the fridge, something with your pair of hygros, the ambient RH in your basement, some "altered" beads (I don't know if that's possible)... just that SOMETHING is screwy.

2. I only say that because of the countless numbers of folks who are using the beads with absolutely no problem. I have personal experience with leaving my humis in an unused (heating vents closed) bedroom where the temps were low 60s (60-63) degs. The humis, both a "humi" and a coolerdor were holding at 69-70%, using 70% beads, and i had no problems for periods of a week or longer (on several occasions). Further, when the room was going to be used (for guests and such), the vents would be opened, and the temps would be climbed up to 68-70 for a few days, with no crazy changes in hygro readings.

I imagine there must be several other users who have experiences with beads in 60 (and possibly even slightly sub-60?) temps.

Anyway, your discussion is advanced far beyond my practical suggestions, but I'd be interested to see, if you use the same setup, including the fridge, same beads, and same hygros, upstairs in temps around 65-75, if the problem will correct itself... my guess is that it will not.

There are so many ways your problem is screwy, I guess, it almost seems there must be something we don't understand about the function of the beads... but I just think this would have come up before, and 80% is a hugely high RH in what (all other things considered) seems like an environment where it would be hard to reach 80% RH without simply putting a bowl of water in there.

Let us know your results when you make some changes.

Thanks for doing so much discussion and explaining!

(I hope this wasn't an unhelpful, annoying post to you!)

[Hydrated]

Well... I must say that the technical discussion in this thread gives me a big 'ol engineering woody!

But seriously... your research into the physics of this has been helpful, but you need an engineering solution (no offense to the physics crowd)... physicists are great at talking about stuff. Engineers are all about the practical application of science. As a systems engineer, here is the strategy that I'd use to solve the problem.

• Verify that there is indeed a problem. I'm not absolutely convinced that there is a problem, though you took steps toward resolving this when you calibrated your hygrometers and thermometers. We haven't really resolved the issue of how temperature affects RH and how those two variables change the moisture content of your cigars. Your cigars may indeed contain the correct amount of moisture for a given temperature and RH.
• Identify the variables involved in the system. It seems that you have identified RH, temperature, container volume, bead volume, bead vapor pressure, mass of container contents, and I'm sure that there are more.
• Determine which variables that you can control. Further identify those variables that you can EASILY control.
• Change one variable at a time, and record the results.

Solution:
The most easily controlled variable in your case is temperature. That is most convenient, because temperature is also the variable that you suspect as being the root cause of your problem. Be careful to change only one variable at a time, otherwise you may solve your problem and still be unable to determine exactly what the problem was.

Bring the whole system upstairs. Unfortunately, this will change two variables: the ambient temperature and the RH of the system's external environment. Sorry, but that's as close as we can easily get to changing only one variable. And we engineers are all about easy.

Note the changes in your system... if changing the temperature variable fails to solve the problem, then you have problems elsewhere in the system.

[SIZE="4"]Baglorious[/SIZE]... you did just fine for a liberal arts type! We'll turn you into a techno-nerd yet! Hell... I was a journalism major in the days before I discovered computers and electronics...

Bobby

[RLembke]

We'll set that term 'net evaporation to the side for now. That's what had me hung up. I would not tie RH to 'net evaporation' at all.

I disagree on the ice being able to maintain it's solid form in a frozen state. I think the air at any temperature below freezing would not be able to maintain a vapor pressure high enough to keep solid water from wanting to sublimate. That's what I'm saying about cigars and their "proper water content" in a climate below 60F. I think even at saturation, air below 60F doesn't have enough moisture content to keep the cigar at equilibrium with the proper amount of water content.

[RLembke]

Hydrated -

Thanks for the comments and the ideas. I began to do just as you suggested last night - move the whole system to a different ambient environment to see what happened. Unfortunately, my appetite for a science experiment and to determine the true factors of my problem was overpowered by my desire to remove the mold issues and 'save the sticks'. I removed all boxes for some time and let the fridge vent to the environment for quite some time. I'm trying to start over with it now. The best I can do it now try to use all the same equipment (beads, fridge, sticks) at the new temp and see where it equalizes at.

Viper has kindly offered to send a new set of beads to see if that corrects the issue. At the same time, we are trying a few different things with the calibration of a hygro at different temps and seeing if other 2-way humidifcation systems such as the Boveda/Humidipaks react in the same way as the beads at low temps. Initially, my hygro indicated a 'calibrated' 62F/80% this AM down in the basement. I've brought the kit up to the room temp area to see what it says here.

My engineery mind still contends that these products, beads or paks, are at the end of the day nothing more than a passive humidification system that can only do their work by means of attempting to maintain a specific vapor pressure in a system regardless of temp. I'm not sure how a material could account for temp change and adjust the desired vapor pressure.

Baglorius -

Your comments are well taken. Your understanding sounds thorough to me! As for whether there is something screwy here, I'm not convinced just yet. I agree that a large number of people have used the beads with no problem but I haven't seen anyone say they have had their humidors at/near 60F for any given length of time and had the RH stay around 65/70%.

[havana_lover]

why dont you try moving into the house part and not the basment?? with a higher room temp I would think things would return to normal..

goodluck

[Scimmia]

Originally Posted by RLembke

I disagree on the ice being able to maintain it's solid form in a frozen state. I think the air at any temperature below freezing would not be able to maintain a vapor pressure high enough to keep solid water from wanting to sublimate.

But what if you were already at 100% RH? The sublimation would still happen, but you would also be getting an equal amount of condensation (frost), and the ice would keep it's mass. That water has to go somewhere, and you're already at 100% RH, right?

Of course, it is possible to go over 100%, but I don't think we'll get into that right now.

With the beads, they don't "adjust" or anything to compensate for temperature, but at a lower temperature, the evaporation rate is lower, that alone could compensate for temperature.

[RLembke]

Theoretically, you're right. If the system however occasionally lost very small amounts of moisture (such as opening a freezer, humidor, etc), that little bit of moisture lost from the environment would immediately be replaced by the ice/cigar until back at 100%.

I'm just trying to say that the whole "70% at any temperature" argument is flawed. 70% at any temperature does not and cannot yield cigars with moisture content to that if held in a 70/70 environment.

At lower temperature, the kinetic energy of both gaseous and liquid water molecules will be lower. Evaporation rate will be lower but so will the condensation rate, right?

What physical changes would take place on the surface of the media to change whether vapor condenses on the surface or not? I'd suggest nothing changes to the media and the only thing that changes is the surrounding vapor pressure that either makes the water want to evaporate or condense.

[Scimmia]

Originally Posted by RLembke

At lower temperature, the kinetic energy of both gaseous and liquid water molecules will be lower. Evaporation rate will be lower but so will the condensation rate, right?

Yes, condensation rate will be lower, but that is because vapor pressure is lower, not necessarily temperature. I found more than one reference that said that condensation rate is directly related to vapor pressure, not to temperature; this disparity between evaporation rates and condensation rates is what makes RH the better measure of moisture content. You have a certain amount of moisture in your cigar, and at high temperatures, it will evaporate quickly, so you need more vapor pressure to return that high amount of moisture to the cigar. At lower temperature, it evaporates much more slowly, so you need a lower vapor pressure to return that low amount of moisture. RH is the measure of this relationship.

Originally Posted by RLembke

What physical changes would take place on the surface of the media to change whether vapor condenses on the surface or not? I'd suggest nothing changes to the media and the only thing that changes is the surrounding vapor pressure that either makes the water want to evaporate or condense.

Except that vapor pressure has nothing to do with the amount of moisture that evaporates, only with how much is returned in condensation. Temperature is what determines evaporation rates.

Edit: This has been one of the best discussions on this subject I've seen at CS, I'm honored to be a part of it, but we do need someone with some real experience and schooling in this area. Please help! I'm barely an amateur!

[RLembke]

Originally Posted by Scimmia

This has been one of the best discussions on this subject I've seen at CS, I'm honored to be a part of it

Amen, brotha! I was just thinking the same thing I was saying outloud to my wife, "I hope my humidity discussion buddy hasn't too annoyed to stop posting!"

Originally Posted by Scimmia

Yes, condensation rate will be lower, but that is because vapor pressure is lower, not necessarily temperature. I found more than one reference that said that condensation rate is directly related to vapor pressure, not to temperature; this disparity between evaporation rates and condensation rates is what makes RH the better measure of moisture content. You have a certain amount of moisture in your cigar, and at high temperatures, it will evaporate quickly, so you need more vapor pressure to return that high amount of moisture to the cigar. At lower temperature, it evaporates much more slowly, so you need a lower vapor pressure to return that low amount of moisture. RH is the measure of this relationship.

The lightbulb just went on as to what you were trying to say earlier about 'net evaporation' - thanks! I missed the discrepancy between temp affecting evaporation but vapor pressure instead affecting condensation. Now that clicks!

Originally Posted by Scimmia

Except that vapor pressure has nothing to do with the amount of moisture that evaporates, only with how much is returned in condensation. Temperature is what determines evaporation rates.

Understood. I guess the better way to ask my question would be - what about the beads gives them the magic 65%-managing quality, regardless of temperature (supposedly). And, whatever that quality is, going back to the first equations I posted, don't the beads have to make some kind of temperature adjustment in order to maintain this RH-managing trait?

Thanks again man.....this has been a very respectful, well thought-out discussion. I expect you to post a complete "Da Way It Is" when this is over!

[Scimmia]

Originally Posted by RLembke

I guess the better way to ask my question would be - what about the beads gives them the magic 65%-managing quality, regardless of temperature (supposedly). And, whatever that quality is, going back to the first equations I posted, don't the beads have to make some kind of temperature adjustment in order to maintain this RH-managing trait?

Now on that, I really have no idea. I think they're more of a buffer than anything, acting the same way that the cedar or even cigars would, but with a much higher holding capacity; adding moisture when the condensation from vapor pressure can't keep up with evaporation, and removing it when the condensation outstrips the evaporation at that temp.

But really, I don't know anything practical, things start getting too messy in the real world

Originally Posted by RLembke

I expect you to post a complete "Da Way It Is" when this is over!

When this is over, I'm gonna take two asprin and go to bed. Thinking this hard hurts!

[RLembke]

A morning update -

The beads (close to completely dry) were put in the frig yesterday and left overnight. When I opened the frig this AM, the temp was 66 and the RH was 80%. The beads were still dry.

Something has happened to the beads. Regardless of the temperature, they will not adsorb moisture to bring the RH below 80%. Time to look into that whole 'recalibration' or 'resetting' of these beads to adjust to a different RH. I'm wondering if that's not what has happened.

Another thought on the beads as they relate to maintaining 65% RH. Assuming a humidor is a closed system, is it accurate to say that the beads are acting to induce equilibrium in the system by mimicing the vapor pressure of saturation?

On another note, here's an interesting article I found this morning. It talks about "saturation deficit" being the statistic to control in a closed humidity controlled environment.

http://www.blackwell-synergy.com/doi...1926.tb06686.x

[RLembke]

Another interesting read on vapor pressure deficit and how it "is an improvement over relative humidity measurement alone" in the control of greenhouse environments, specifically in maintaining healthy plant growth while avoiding mold and disease conditions.

http://ohioline.osu.edu/aex-fact/pdf/0804.pdf