Absolute Humidity.

[Joshtupps]

Currently having a discussion on a Facebook group with a fellow cigar smoker who is under the impression that Relative humidity quote "doesn't mean s**t" and that absolute humidity is what we measure in our humidors. This has confused me and I thought I'd ask the ladies and gentlemen here with far greater minds than me to explain which one we are concerned about as I always thought it to be RH...as in the relative amount of moisture in the air compared to what it CAN 'carry' so to speak.

Thank you in advance.

Tupps

[asmartbull]

This argument has been around for decades and there is a lot written on the subject. Don't waste your time arguing....it is RH

" With your shield, or on it"...

[Joshtupps]

Thanks Bull, It's a rather interesting discussion, which has now become very once sided and rather insulting if I'm honest. People cannot take being wrong these days can they? It's ok to say "I misunderstood, thanks for clearing that up".

Tupps

[gr8eman]

Isn't that an argument for weathermen? What difference does it make with a humidor? I have a large wine refrigerator sealed and lined with cedar with a humidifier I keep set at 70% for aging. If you measure the RH at the bottom it's always going to be different but in the ballpark. Conversely, with a regular box humidor with a moist thing you have to periodically fill with water the Rh will go lower slowly if you're in a normal climate. Either way to me the argument seems irrelevant.

[Colt45]

and that absolute humidity is what we measure in our humidors.

I'm no scientist, but I think if we're using a hygrometer which shows humidity as a percentage then we are measuring relative humidity. My understanding of absolute humidity ( and it's not much ) is that it shows the water vapor in a given volume of air regardless of temp, and is measured as a weight.

Someone will be able to shed more light....

[Fugu]

I always thought it to be RH...as in the relative amount of moisture in the air compared to what it CAN 'carry' so to speak.

Absolute....absolutely correct explanation, Tupps!

[PapaDisco]

Hang on fellas . . . you're all assuming consistent temperatures. If your temperature never changes, then rH will absolutely correlate with the moisture content in your cigars. I suppose that's why this other character is going on about "absolute" water content in the cigars. Yes, that's a better data point to aim for, but it's much more difficult to accurately measure than rH, and as we all know rH is a bit of bear to wrestle down to the last percentage point accurately.

If your temperature is kept stable, or relatively close to stable, then rH is the easier thing to manage to, IMHO.

[Fugu]

That's not actually what Tupps said, PapaDisco. May be that that's what the other guy is alluding to (which, however, I don't reckon, as Tupps cites him with "Relative humidity quote "doesn't mean s**t" and that absolute humidity is what we measure in our humidors"), but still the water content in tobacco is closely related to the atmosphere's rH and not to aH (Piggy would say at this point - please do a search within the forum if you'd like some further edification...).

And yes, temperature does also come into play here, as our hygroscopic matter called tobacco tends to hold slightly different amounts of water (equilibrium moisture) for the same rH at varying temperatures (slightly higher water content for lower temps at a given rH). But this is minimal in comparison and not to be confused with the effect of temperature on relative humidity of a gas.

In actual fact, all current metrology standard techniques (filament, chilled mirror dew point, psychrometer, semicond. sensor) "sense" the physical effects of the relative humidity of gases. The absolute one always has to be recalced from the temperature (and pressure), which has to be closely monitored in parallel.

[PigFish]

What you are really after is percentage moisture content of tobacco. What is it that we say about skinning a cat?

I have always considered aH as a calculation based on rH and temperature (altitude or pressure). I suppose that there are likely different ways to determine it with various instruments that range from costing a lot, to difficult to use! I mean, I know you can use desiccants with known isotherms and perform differential weight calculations (for example). I have never really needed to look outside the box for aH certainly due to the fact that rH is far simpler to acquire. You can see the link by pulling up various psychrometric charts and following and connecting the lines. What those lines don't tell you, is what the corresponding EMC of the tobacco is based on those numbers. It is a whole different science, the study of water activity and hygroscopicity verses psychrometry.

I would have to think on this a while, but my gut feeling here is that he is as much right as he is wrong. aH can be worked into and out of EMC equations the same as rH. It is just a matter of conversion. It is however impractical to do as it either requires additional steps to calculate or more expensive equipment or more complex procedures to simply net the same result. In any case, if the argument is being made that temperature is irrelevant, the person is totally wrong. Hygroscopic materials, even salts will have a temperature component.

I think in some ways, at least on the face of it, this is an argument over the centimeter or the inch. Each is a unit of measurement and the practically of each is part personal preference and part the ease at which you can attain the instruments required to measure it.

The fact is, the knowledge of grains/pound of water in mixed in air is just a useless as the saturation vapor pressure ratio verses that of the ambient, by itself. Neither is going to tell you PMC content, not in tobacco anyway, not without the temperature and an accurate, empirical evaluation of tobacco to reference (an isosteric or isothermal chart).

Frankly, I don't think the argument is worth making, nor me giving any additional though to...

I would have to really get into the numbers here in order to really speak definitively and close the door on this argument, and like I said, I don’t really care, so I don’t think I am going to bother with it.

Here is what I am going to leave you with. It has more to do with Piggy the cynic, than it does Piggy the scientist. Follow along friends and see if this makes any sense to you at all.

Over the years have studied literally hundreds of articles and white papers regarding tobacco as a hygroscopic material. Getting (relevant) data on the subject is not really that easy. Of the many papers that I have read, all run by research scientists, some funded inside and outside of the tobacco industry, not one is aH centric. So I have to ask you, if all the research material that I can lay my hands, where none of it uses aH in place of rH as a means to measure PMC, what does that say for the argument?

If aH, regardless of temperature, or even inclusive of temperature was the magic bullet to tobacco storage, it would be all over the many scientific papers I have read, and it would be a key witness to the processing of tobacco, especially in cigarettes. Let me remind you, cigarettes are a billion dollar industry, where they can afford the best of the best in research. As a cynic, I have to say that the odds are, the guy is out to lunch.

If you want to run back to Farce-book and win this argument, simply ask for the evidence! Ask for an chart where aH is plotted against EMC, where EMC is a factor of aH alone. Ask for the white papers proving the argument. Hell, I would love to have that data!!! Without that data, assuming it is accurate and truthful, the guy is talking out his anus!

Any and all evaluations of EMC I have ever seen are three variable representations of EMC to temperature and rH. I have never seen one at all even referencing aH… It is not really relevant. It might be relevant secondarily when it comes to air conditioning a cigarette plant (as in factory) but beyond the world of HVAC and energy conservation I see no need to consider it for the ‘condition’ of tobacco.

So with that my friends and 5 cents, go get yourself a nickel cigar!

Cheers! -Piggy

[PigFish]

Paul, I was able to find a scaled redraw of a chart of PMC of tobacco to rH and temperature. I know that you have wanted this for a long time. It is in PDF.

I cannot recall if I have your email, so send it to me at my cigarclimatology em and I will get it off to you.

Cheers, -Ray

[Fugu]

Paul, I was able to find a scaled redraw of a chart of PMC of tobacco to rH and temperature. I know that you have wanted this for a long time. It is in PDF.

I cannot recall if I have your email, so send it to me at my cigarclimatology em and I will get it off to you.

Cheers, -Ray

Ray, just seeing this now. Great! PM sent.

Cheers,

Paul