Water content vs relative humidity


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Just wanted to take a second to say thanks to all who have weighed in on this topic.  No doubt I can appreciate the frustration and feeling of ground hog day when the same questions and fallacies come up over and over but, rest assured, the time you take to respond is much appreciated and is certainly helpful in assisting us in gaining a better understanding of this critical component of protecting and enjoying this hobby. All the instructional videos on lighting and cutting a cigar certainly seem like overkill but delving into this desire to create a relatively stable, ideal RH environment for our cigars to maximize the enjoyment can certainly get incredibly complicated! Nonetheless, with each discussion I read I do learn something new so thank you again to all for taking the time to post!

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14 minutes ago, Schumi5 said:

Just wanted to take a second to say thanks to all who have weighed in on this topic.  No doubt I can appreciate the frustration and feeling of ground hog day when the same questions and fallacies come up over and over but, rest assured, the time you take to respond is much appreciated and is certainly helpful in assisting us in gaining a better understanding of this critical component of protecting and enjoying this hobby. All the instructional videos on lighting and cutting a cigar certainly seem like overkill but delving into this desire to create a relatively stable, ideal RH environment for our cigars to maximize the enjoyment can certainly get incredibly complicated! Nonetheless, with each discussion I read I do learn something new so thank you again to all for taking the time to post!

Amen!  I have read plenty of similar threads, but the repetition of certain information and the inclusion of new information has made it so I may finally be understanding some of it.

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1 hour ago, Schumi5 said:

Just wanted to take a second to say thanks to all who have weighed in on this topic.  No doubt I can appreciate the frustration and feeling of ground hog day when the same questions and fallacies come up over and over but, rest assured, the time you take to respond is much appreciated and is certainly helpful in assisting us in gaining a better understanding of this critical component of protecting and enjoying this hobby. All the instructional videos on lighting and cutting a cigar certainly seem like overkill but delving into this desire to create a relatively stable, ideal RH environment for our cigars to maximize the enjoyment can certainly get incredibly complicated! Nonetheless, with each discussion I read I do learn something new so thank you again to all for taking the time to post!

With a little bit of friendly sarcasm to keep us amused, the forum is filled with all forms of generous people that generally help just about anyone navigate pearlis journey of separating cigar fact from phallicy.

Just don’t start another damn plume thread!

-the Pig

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23 hours ago, bpm32 said:

I'm also delighted to be proven wrong, because it makes for great discussion, and I could totally be wrongheaded in what I've said above, so have at it!

Here we go :P, but I guess a simple glitch here - and you meant to say rH rises...:

23 hours ago, bpm32 said:

I say that lowering the temperature would lower the RH ....

 

> 1. I think we might be talking past each other on the water in the cigars thing. When I mention the total number of water molecules I literally mean every water molecule in the system, including the molecules buried deep in the cigar. They are all trying to attain equilibrium for the given temperature and pressure. I say that lowering the temperature would lower the RH without regard to the water in the cigar because the water in the cigar cannot respond (either give up or suck in more water) to attain equilibrium for the new state of the system quickly enough. This would take something on the order of hours (or days?), and is based on mass diffusion, and could probably modeled on solvent loss in hydrogels or organogels. <

Now, are we talking "concept rH" and its effect on tobacco moisture here, or the forced adjustment thereof in response to temp. changes?

The case in point you had brought up has been the former, therefore, no, this all is not a function of time. In the current approach we are dealing with equilibrium state, i.e. after reaching steady state. In this thermodynamic consideration, we leave aside time and with that any diffusion processes and gradients. That is, gradients of concentration, heat, pressure or convection gradients. This is not factoring in here. Like the freezing point of an aqueous solution is not determined by the duration of chilling, the solubility of a salt in a solvent is not depending on the extent or duration of mixing.

So this conception already is a flawed one.

Methodological, as you notice yourself - all impractical! Well aware of how water content can be determined analytically in a sample. But that is completely missing the point here. As postulated above - non-destructive, practical means! Doesn't help to kill the cigar under observation. This is about storage, not analytics. That's a side-show actually. What we are aiming at in cigar storage, is - less than we need to know what the actual moisture of that tobacco in numbers really is (Piggy and myself are in full agreement that we don't, apart from perhaps to analytically determine temp.-coefficients) - we do need to know how to keep, monitor and maintain it on a stable level. Ultimately, there is no other way than by controlling the storage's climate. Really no other way, and nothing really debatable here.

> You could theoretically have an RH for other solvents (you could determine how much gaseous diethyl ether air can hold at a given pressure and temperature, for instance), but this would sound weird. With concentration or mass fraction you always know where you stand with all gases, not just gaseous water, and I feel it is intuitive. <

Absolutely! Analogous. But we are dealing with hygroscopicity here. Water is it what matters.

And while you have an academic background (that's at least what I read from your posts), your view appears very closely focussed on your own particular field of work. Try and get more disengaged from what hinders you to gain a proper understanding of this very field, which we are discussing here. You'd probably have a different view of it were you coming from meteorology, climatology, life- or food sciences, and/or perhaps one of the basic fields of physics or metrology.

> I have to take issue with the idea that cigar storage isn't like rocket science- <

You'd never hear such from me! :D  (and not what I said)

> 3. What my problem with RH? Well, it's basically a pedagogical one. It is not intuitive that dropping the temperature in a closed humid system would have a huge RH effect, so I have trouble explaining the concept to students. Even Chemistry PhDs look at me blankly at first (basic stuff like this gets forgotten in the path from high school through grad school). <

Granted, it's not exactly trivial. Threads like this prove it over and over again. Still, not overly difficult either. But the fact that the parameter 'relative humidity' doesn't appear intuitive (well, for some it does) doesn't make it wrong, or make it the wrong variable to consider within this framework here. Most quantum mechanics isn't much intuitive either, still.... That's really remarkable reasoning. If today's students can't grasp it, that's not the fault of the parameter. It's more telling about today's students (or perhaps their lecturers ... haha  ;))

No hard feelings, but I think that discussion doesn't really bring us any new conclusions.

 

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On 1/10/2019 at 1:00 AM, PigFish said:

One problem that you are going to have is wet cigars! Why... Because as temperature rises, as you increase water content in space to meet your isotherm for PMC, you load your cigars with water. Then as the temp goes down you ask the cigar to give up water.. Simple right? Not really. The problem is that cigars are far more apt to transfer water at higher temps than at lower temps. This means that you can potentially load a cigar with water, or decrease it for that matter, at a faster rate in higher temps than at lower temps.

This is a really important point that must not be missed! This effect and also the effect that, for a given constant temperature, the water transfer rate for drying and moistening is never symmetrical. That is, its adsorption- and desorption-isotherms are hardly ever equal. Usually working in the same direction as for the above temperature effect - drying/unloading moisture taking longer than loading up.

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1 hour ago, Fugu said:

Here we go :P, but I guess a simple glitch here - and you meant to say rH rises...:

 

> 1. I think we might be talking past each other on the water in the cigars thing. When I mention the total number of water molecules I literally mean every water molecule in the system, including the molecules buried deep in the cigar. They are all trying to attain equilibrium for the given temperature and pressure. I say that lowering the temperature would lower the RH without regard to the water in the cigar because the water in the cigar cannot respond (either give up or suck in more water) to attain equilibrium for the new state of the system quickly enough. This would take something on the order of hours (or days?), and is based on mass diffusion, and could probably modeled on solvent loss in hydrogels or organogels. <

Now, are we talking "concept rH" and its effect on tobacco moisture here, or the forced adjustment thereof in response to temp. changes?

The case in point you had brought up has been the former, therefore, no, this all is not a function of time. In the current approach we are dealing with equilibrium state, i.e. after reaching steady state. In this thermodynamic consideration, we leave aside time and with that any diffusion processes and gradients. That is, gradients of concentration, heat, pressure or convection gradients. This is not factoring in here. Like the freezing point of an aqueous solution is not determined by the duration of chilling, the solubility of a salt in a solvent is not depending on the extent or duration of mixing.

So this conception already is a flawed one.

Methodological, as you notice yourself - all impractical! Well aware of how water content can be determined analytically in a sample. But that is completely missing the point here. As postulated above - non-destructive, practical means! Doesn't help to kill the cigar under observation. This is about storage, not analytics. That's a side-show actually. What we are aiming at in cigar storage, is - less than we need to know what the actual moisture of that tobacco in numbers really is (Piggy and myself are in full agreement that we don't, apart from perhaps to analytically determine temp.-coefficients) - we do need to know how to keep, monitor and maintain it on a stable level. Ultimately, there is no other way than by controlling the storage's climate. Really no other way, and nothing really debatable here.

> You could theoretically have an RH for other solvents (you could determine how much gaseous diethyl ether air can hold at a given pressure and temperature, for instance), but this would sound weird. With concentration or mass fraction you always know where you stand with all gases, not just gaseous water, and I feel it is intuitive. <

Absolutely! Analogous. But we are dealing with hygroscopicity here. Water is what matters.

And while you have an academic background (that's at least what I read from your posts), your view appears very closely focussed on your own particular field of work. Try and get more disengaged from what hinders you to gain a proper understanding of this very field, which we are discussing here. You'd probably have a different view of it were you coming from meteorology, climatology, life- or food sciences, and/or perhaps one of the basic fields of physics or metrology.

> I have to take issue with the idea that cigar storage isn't like rocket science- <

You'd never hear such from me! :D  (and not what I said)

> 3. What my problem with RH? Well, it's basically a pedagogical one. It is not intuitive that dropping the temperature in a closed humid system would have a huge RH effect, so I have trouble explaining the concept to students. Even Chemistry PhDs look at me blankly at first (basic stuff like this gets forgotten in the path from high school through grad school). <

Granted, it's not exactly trivial. Threads like this prove it over and over again. Still, not overly difficult either. And the fact that the parameter 'relative humidity' doesn't appear intuitive (well, for some it does) doesn't make it wrong, or make it the wrong variable to consider within this framework here. Most quantum mechanics isn't much intuitive either, still.... That's really remarkable reasoning. If today's students can't grasp it that's not the fault of the parameter. It's more telling about today's students (or perhaps their lecturers ... haha  ;))

No hard feelings, but I think that discussion doesn't really bring us any new conclusions.

 

Oh, I don't mean to imply that any of my ramblings add any new conclusions, but this is a subject I haven't thought too deeply about before. I am painfully aware that you don't get much out of a rehashed conversation like this, so I do appreciate the time you've taken with your thoughtful responses. Nothing I've mentioned is actionable or would help people store cigars better. I think that's pretty well figured out and right now all that remains to be done is engineering--that is, how to economically and practically hold cigars at stable temperature and humidity indefinitely. 

For assaying water in cigars--same thing. Why do it? No real reason to except it might be interesting if you could put numbers on things, as in "Cuban tobacco typically equilibrates to X% to Y% water by mass if you store them at perfect 65%/65°" or "as time proceeds and oxidative crosslinking predominates, cigar swelling behavior decreases via such-and-such curve for arbitrarily defined temperature and humidity." Actionable though? Helpful even? Nah... 

Regarding today's students--a teacher gets more knowledgeable, but the students reset to a basic level of dumbness every semester. Same case here: we're the students and you're the teacher, but you've got new guys like me who wander in off the street and into this subject. While I suppose cigar guys are in general successful in life (how else could we afford to blow so much money on an unnecessary luxury?), expertise in one subject doesn't translate into knowledge about another. I cannot help but look at the world through the lens of the basic physical sciences, and while that is not factually wrong, it usually isn't a productive or efficient way to look at things. If it were, everything would to reducible to theoretical physics and we wouldn't even have chemistry or biology, let alone climatology or meteorology.

Regarding your question, "Now, are we talking "concept rH" and its effect on tobacco moisture here, or the forced adjustment thereof in response to temp. changes?", definitely the latter. So, say that a novice cigar dude has control over the RH, but not the temperature, and the cigars are allowed to range plus or minus 8 degrees; that is, what does the plot of temperature in that 16 degree range look like vs. equilibrium water content? Is it large enough to matter practically? Obviously these conditions are far from ideal. I could have sworn I saw some old journal articles about this on cigarette tobacco, but now I can't find them. From some brief browsing of plant biology articles just now (always dangerous because I don't know a damn thing about biology), it looks like the temperature dependance on swelling is negligible at ambient temperatures, but then again tobacco might be some weird special case where water content at equilibrium changes a lot.

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Fair enough, and well put! Sorry, I didn't mean to choke off the thread. You are right, there's always new people coming on board keen to learn about and discuss the topic, but having missed the older 'ramblings'. Likewise, it then wouldn't feel right for those in the know to keep a back seat, while watching things going astray to the detriment of other LOTL. So, indeed true, the recurrence of such threads appears somehow inevitable. And still, every now and then even something new to be discovered. In that regard, it cannot be valued highly enough what @PigFish has been compiling over the years, and never tires to repat. Strongly recommended to browse that pool of information (tip: his video tutorials are comparatively "concise" compared to his posts... haha :peace:)

19 hours ago, bpm32 said:

Regarding your question, "Now, are we talking "concept rH" and its effect on tobacco moisture here, or the forced adjustment thereof in response to temp. changes?", definitely the latter. So, say that a novice cigar dude has control over the RH, but not the temperature, and the cigars are allowed to range plus or minus 8 degrees; that is, what does the plot of temperature in that 16 degree range look like vs. equilibrium water content? Is it large enough to matter practically?

Ok, in that case, I can only refer again to what has been said above regarding hysteresis. If one lets temperature swing, and in particular by that much, I say, forget about getting your mind twisted around fine-tuning humidity control algorithms. What then actually happens in the cigar is out of one's control.

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On 1/11/2019 at 11:47 AM, bpm32 said:

Regarding your question, "Now, are we talking "concept rH" and its effect on tobacco moisture here, or the forced adjustment thereof in response to temp. changes?", definitely the latter. So, say that a novice cigar dude has control over the RH, but not the temperature, and the cigars are allowed to range plus or minus 8 degrees; that is, what does the plot of temperature in that 16 degree range look like vs. equilibrium water content? Is it large enough to matter practically?

... I think it does. If I am throwing numbers around, depending on the actual temperature range that you are discussing, it matters a lot. 16F won't matter at the extremes. In those cases water is either locked into the cigar due to relative inactivity, or there is no water in the cigar again due to relative activity.

However in the range that we typically discuss, room temperature, I would say that the equivalent rH is around +- 2.5, meaning 5 rH total swing.

This brings us full circle then. While the rH is dominant factor, temperature is rH (rhetorically speaking) when you look at their relationship to EMC.

If one has a belief that EMC plays a major role in the taste of a cigar, and I do, then it behoves one to control both variables as much as one can afford to control them. If one values their time, and therefore their smoking time, cost of the cigar itself notwithstanding, one should do what one can to make the experience as good as it can be. Controlling PMC is the easiest way I know to do that... with the possible exception of smoking in a strip club!

Cheers! -the Pig

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