Understanding Percent Moisture Content: A discussion of the relationships between rH and Temperature in Cigar Storage


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What a great thread. Thanks for posting. I now know why my stock is smoking too wet during the winter months. Ray, you wouldn’t happen to have “the math” underlying the charts lying around would you? I ask because I would be more than willing to build it into a spreadsheet that members could use to “plug & play” - meaning if they’re trying to achieve an exact PMC given a fixed temp or RH, the spreadsheet would output the correct settings. Would take a little guesswork out of the process and maybe get more people to start tracking their numbers and getting more familiar with PMC. I think that could help to elevate our discourse on the subject, and hopefully even lead to better smoking experiences.

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  • 3 months later...
On 2/19/2019 at 1:13 AM, JeffreyLebowski said:

I would be more than willing to build it into a spreadsheet that members could use to “plug & play” - meaning if they’re trying to achieve an exact PMC given a fixed temp or RH, the spreadsheet would output the correct settings. Would take a little guesswork out of the process and maybe get more people to start tracking their numbers and getting more familiar with PMC.

Oh man—this would be great!  Especially for beginners like myself.

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  • 1 month later...

This info is fantastic. I recently realized I need to control my temp to avoid RH swings and to have a consistent smoking experience. I have a few questions:

1) What is the ideal moisture content (MC) for Cuban tobacco (seems like this is not well documented)?

- It appears that the answer will be related to a few variables a) What is the ideal MC for aging? b) what MC do I prefer?

- Does anyone have a feel for this so I can pick the temp / RH range to maintain my collection?

2) Is there an instrument to measure moisture content in cigars non-destructively?

- I would like to measure MC to find out what I prefer the most. 

- I have found some inexpensive instruments to measure MC in wood. Perhaps these will work. Suggestions?

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  • 3 weeks later...

Ray, this is interesting stuff, thanks for your effort researching this, and your patience explaining it

I was looking into the debates about relative humidity / temp / absolute humidity / moisture content, and found your posts about all this on the forum. I'm more interested in this out of curiosity than finding the perfect setup (I only have a tupperdor at the moment, so fine tuning temps isn't an option anyway).

I found some abstracts of papers looking into modeling equilibrium moisture content for tobacco, and it seems that models like BET and GAB are a good fit (example here), but I don't understand the equations (I could probably figure them out eventually, but I've already disappeared way too far down this rabbit-hole already :)) and even if I did, there are probably specific values to use for the coefficients that tune the model for tobacco.

The one EMC model that I could find a useable equation for is the Hailwood-Horrobin model from the Wikipedia page on EMC, it's tuned for wood, but the numbers seem pretty close to the graph that you showed in your video (see the graph below). Have you found a better model in your digital travels?

EMC.thumb.png.48200a2404a8a2e93d0ce3ce5aecf213.png

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Can someone (@PigFish?) please explain the science of this relationship to me? This model claims that, to maintain the same moisture level in a cigar at a higher temperature, you need to raise the relative humidity as well. But I thought that the same relative humidity at a higher temperature meant more moisture, since warm air can hold more water...

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1 hour ago, corneliusmaximus said:

Can someone (@PigFish?) please explain the science of this relationship to me? This model claims that, to maintain the same moisture level in a cigar at a higher temperature, you need to raise the relative humidity as well. But I thought that the same relative humidity at a higher temperature meant more moisture, since warm air can hold more water...

You are comparing the bonding of water vapor to a hygroscopic substrate to free water vapor in space. That is the key to most that misunderstand the relationship. They are not the same.

More when I have the time. For now, consider what you know about what happens when you heat water and it boils...

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And if I'm understanding correctly, this model recommends that to retain the same moisture of the cigar,  for each increase in 1dF, you should also raise rH by 0.33%. Correct?

To give an example, if it's hypothetically optimal to keep a certain cigar at 65F / 62%, then to adjust to an environment of 71F,  you would calculate 62 + (0.33 x 6) = 64%.

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  • 4 weeks later...

@PigFish 

That was a great video! I will definitely be sharing this.

Is PMC the main factor that affects cigars? I read that for long term cigar storage people tend to store cigars at cooler temperatures of about 55-65 degrees and 65%rH. According to video this means PMC would be about 14-16%. But I can also achieve 14-16% PMC using higher temperatures. So why do people tend to store cigars at lower temperatures?

Doesn't a lower temperature increase risk of mould? Also at what temperature do cigar weevils / beetles grow?

Thanks!

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8 hours ago, Danny_Cigar said:

Doesn't a lower temperature increase risk of mould? Also at what temperature do cigar weevils / beetles grow?

Mould/mold tends to prefer warm and humid conditions.

And below 18 C is recommended to deter beetle activity at all life stages, which interestingly enough is inline with the 16-18 C degree storage temps that HSA recommends.

https://www.researchgate.net/publication/249887786_Low-temperature_as_an_alternative_to_fumigation_to_disinfest_stored_tobacco_of_the_cigarette_beetle_Lasioderma_serricorne_F_Coleoptera_Anobiidae

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14 minutes ago, sho671 said:

Mould/mold tends to prefer warm and humid conditions.

And below 18 C is recommended to deter beetle activity at all life stages, which interestingly enough is inline with the 16-18 C degree storage temps that HSA recommends.

https://www.researchgate.net/publication/249887786_Low-temperature_as_an_alternative_to_fumigation_to_disinfest_stored_tobacco_of_the_cigarette_beetle_Lasioderma_serricorne_F_Coleoptera_Anobiidae

Interesting. Thanks for this.

Are cigar beetles still a common problem in current times? I read that manufacturers freeze the tobacco or cigars. 

At the moment I'm storing cigars at room temperature of about 73.5f (22.7 C), do you think this is a cause for concern?

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  • 1 month later...
On 7/12/2020 at 10:44 PM, Danny_Cigar said:

Interesting. Thanks for this.

Are cigar beetles still a common problem in current times? I read that manufacturers freeze the tobacco or cigars. 

At the moment I'm storing cigars at room temperature of about 73.5f (22.7 C), do you think this is a cause for concern?

Very interesting read this topic. I am also a bit worried, normally mine is reading between 69 (20,5°C) to about 73 (22,7°C) degrees Fahrenheit, but lately there was a heat wave measuring between 90 and 100 degrees Fahrenheit outside for several days. Although i am keeping them in the basement  for now, there were still some temperature swings up to 75 (23,8°C) - 77 (25°C) degrees Fahrenheit in my humidor. So in normal conditions i keep it at 69% RH (This corresponds roughly with 12 and 3/4 of the PMC value's Y-axis). But with this heat surge, and also following the data on this chart, the hotter it gets, the more the PMC value begins to drop when maintaining a constant RH of 69%. So let's say i want to maintain a certain PMC Value I'd have to up the RH value aswell. So if im reading this chart by MettleMonkey right, an increase of 2% RH is causing + 0,5 (of a percentage) difference on the Y-axis (PMC value) for let's say 70 degrees F on this chart (as depicted). So knowing this and the temperature goes up with 4 to 8 degrees Fahrenheit in my case, and for the sake of keeping it simple, let's say 5 degrees Fahrenheit, this increase of temperature causes a drop of only - 0,125 (of a percentage) on the Y-axis...

This situation was before reading this topic, so i upped my humidifier to reach 71% RH (so 2% up). So if i am getting what you're trying to say with this chart correctly, minor adjustments to the RH value have big effects on the PMC-value? And when it comes to coping with these increases in temperature, adjusting it with 1%RH, would do the trick for a 4 ~ 8 °F increase in my case?

I better go and tone it down a little then tomorrow, up to about 70%RH. Also a bit afraid of having too much humidty, but then again: everywhere on the internet you are reading between 65%RH and 75%RH is between the limits. Too bad i can't regulate the temperature the way i want in here.

 

 

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