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

[Scimmia]

hmm, you could be right, but how can we just add a random amount of water to our beads and it keeps the humidity at a very consistant RH? You would think they would need measured or something if they were strictly buffer.

Edit: After some more reading, I'm thinking you're right; maybe the amount of water we're adding just isn't high enough compared to the adsorbtion abilities of the silica gel to make that much difference, and maybe that's where you got in trouble.

[RLembke]

I did a little playing around with those VPD equations this morning and put together a chart showing the VPD equivalent RHs for a range of temps. This shows what RH would give the equivalent vapor pressure deficit of 70F/65% or 70F/70% across the temperature range.

Scimmia or anyone else...if you'd be interested in seeing the speadsheet, shoot me a PM with your email and I'll send it over.

Here's the chart.

Edit - following the VPD logic, my 60F/80% environment would be equivalent to 70/86%! And from the Padron I had last night...yeah, not good at all.

[Scimmia]

You know, I think I'm going to have to see if I can find any more info on VPD, both VPD and RH take into account the relationship between temperature and vapor pressure, but the more I think about it, the more I wonder if VPD is correct; the papers talk about using it because of mold/disease issues, not specifically moisture content, and that article on silica gel specifically states that RH is what effects moisture content. Plus the fact that if your cigars were really at 70F/86% equivalent for a couple of days, I would expect them to be completely split open.

Very nice chart, though, I love how it's more of a direct relationship vs the inverse relationship with RH that's always posted in the AH tables.

[Hydrated]

Originally Posted by RLembke

I did a little playing around with those VPD equations this morning and put together a chart showing the VPD equivalent RHs for a range of temps. This shows what RH would give the equivalent vapor pressure deficit of 70F/65% or 70F/70% across the temperature range.

Scimmia or anyone else...if you'd be interested in seeing the speadsheet, shoot me a PM with your email and I'll send it over.

Here's the chart.

Edit - following the VPD logic, my 60F/80% environment would be equivalent to 70/86%! And from the Padron I had last night...yeah, not good at all.

[SIZE="5"]Owwwww!! My brain... it burns... make it stop!![/SIZE]

He used charts!!! Stop... owwwww...

Excuse me while I go claw my eyeballs out...

[madurolover]

Originally Posted by Hydrated

[SIZE=5]Owwwww!! My brain... it burns... make it stop!![/SIZE]

He used charts!!! Stop... owwwww...

Excuse me while I go claw my eyeballs out...

[RLembke]

Originally Posted by Scimmia

.....and that article on silica gel specifically states that RH is what effects moisture content.

I keep trying to find a good explanation of that theory.

I do this the AH argument is over now that we found this VPD value and it does seem to make more sense but now the question comes up, which is the better way to think about the VPD - as a percentage (which is RH) or as a specific value not to be varied by temperature.

[Isombitch]

We have to assume your hygrometer is correct and it really is 80% RH. Next step, measure ambient RH just outside the fridge.

1. If it is dry, you have something in the fridge giving off H2O. Find it or get a coolerdor.

2. If it is humid outside the fridge. You have a serious seal problem. (my bet)

Steve

[kjd2121]

Originally Posted by Isombitch

We have to assume your hygrometer is correct and it really is 80% RH. Next step, measure ambient RH just outside the fridge.

1. If it is dry, you have something in the fridge giving off H2O. Find it or get a coolerdor.

2. If it is humid outside the fridge. You have a serious seal problem. (my bet)

Steve

I would eliminate the fridge altogether and see what happens in a cooler. -

[Scimmia]

Ug, everything I'm finding says that there is disagreement on whether RH or VPD is the best way to measure atmospheric moisture for plant growth; I can't find any information on actual moisture content.

My head's starting to hurt again...

[RLembke]

This is a pretty amazing article I just found.

Full link - http://www.microcool.com/cooling/bro...ityControl.pdf

"Humidity Control Algorithm in the Greenhouse" - Michael A. Dixon, PhD, University of Guelph (Ontario, CA)

Here's the 'juicy bits" -

Before I continue with a description of some of our experiments, it seems appropriate to add a
brief discussion of the terminology associated with the study of humidity. To a certain degree, many of the
misconceptions and inaccuracies related to the interaction between humidity and plants have been fostered
by the way we measure and talk about humidity. The average individual uses the term “relative humidity”
with confidence and ease. Humans have a general “feel” for this assessment of atmospheric moisture that
makes it relevant to their relationship and interaction with the aerial environment. It seems natural,
therefore, to continue to apply this measure of humidity in research associated with greenhouse humidity
control or in attempting to outline a management strategy of humidity control in the greenhouse.

Relative humidity, as we are all reasonably well aware, is a measure, in percent, of the amount of
water vapor in the air compared to the total amount of water vapor that could be in the air at a given
temperature. Of course, as the air temperature rises, its capacity to hold water vapor also increases and,
conversely, as air temperature falls it will hold less and less water vapor. So, arriving at this common
measurement of aerial moisture requires knowledge of the relationship between water vapor concentration
(or partial pressure) and air temperature. This allows us to predict the absolute maximum quantity of
moisture that the air will hold at a given temperature which we then divide into the actual quantity of
moisture present at the time of our measurement and multiply by 100 to arrive at “percent relative
humidity”. Sadly, mental arithmetic is a lost art in this age of the computer so the trusty hand held
calculator (or its equivalent in the circuitry of most solid state sensors) helps us to the final answer.
Unfortunately, even the most sophisticated, genetically manipulated plant species has yet to master the
simple calculator or even simpler mental arithmetic to achieve this evaluation of humidity.

Plants cannot respond to or detect moisture that is present in the air (until it condenses or falls on
them) but instead respond to atmospheric demand for moisture, which is another way of defining the
moisture that is not present in the air. That is the vapor pressure deficit and is the difference between
the actual concentration or partial pressure of water vapor in the air and the maximum possible
concentration at that temperature. It doesn’t require that the plant have any knowledge of arithmetic or
predictive relationships. The plant simply opens its stomatal pores as the sun rises and permits the
evaporation of water from the leaves in response to the atmospheric demand established by prevailing
ambient conditions. If the atmosphere becomes too demanding, plants exercise a variety of mechanisms to
cope and still maintain physiological functions. Viewing humidity from the plant’s perspective was the
first step in approaching a rational strategy of humidity control.
Therefore, all of our measurements of humidity which were to be correlated with plant
physiological and growth responses were evaluated as vapor pressure deficit (VPD) rather than relative
humidity (RH). Our greenhouse environment control responded to VPD feedback and our set points were
established in units of millibars (mb) which is a pressure unit. Concentration units (eg. g/m³) are also
common. To put the units in perspective, a VPD of 10 mb at a temperature of 20 C represents a relative
humidity of about 56%, 10 mb at 30 C is closer to 76% RH. TO make the point about atmospheric demand
more clearly, 80% RH at 20 C represents a VPD of about 4 mb. Raising the temperature to 30 C but
maintaining the same 80 % RH results in a VPD of 8 mb. Thus, even though the relative humidity
remained unchanged, the atmospheric demand for moisture felt by plants was doubled.

[Scimmia]

Been looking around a bit more, and I found this page for moisture content of wood:
http://www.csgnetwork.com/emctablecalc.html

It shows the same basic thing as your graph. I'm calling it, I think you've got it, time for YOUR "Da Way It Is" post!

Edit: We should have been looking at Equilibrium Moisture Content all along!

[Malik23]

So, someone want to put all of this into layman's terms and give us concrete guidance on how we should handle temperatures outside the 65-75 range using beads or otherwise?

[Scimmia]

Many of the people who talk about 65% RH have said to use 65%/65F instead of 70%/70F. If you look at the graph, they would BOTH have very similar amounts of moisture in the cigars. Interesting...

Malik, basically follow the chart that RLembke posted, most likely using the 70%/70F line as a reference. Any method you want to use to control RH should be fine, beads included.

Hopefully he'll make one big post with a quick summary of everything that can be stickied (unless the FOGs can find issue with all of this) and we can avoid getting the ridiculous absolute humidity charts posted all of the time.

Edit: out of curiosity, what is the VPD at 70%/70F?

[Malik23]

Hmm, I guess the one thing I am really taking from this discussion is that regardless of what humidity option I use, temperature control is essential to the storage of cigars.

[RLembke]

I was out of town for the weekend and it provided a nice time to think about how to proceed from here.

This thread really has two topics going right now. The one I wish to continue now is the VPD vs RH measurement of humidity and which is best for cigars. I will start a new thread for that shortly. The second topic concerns the ability and function of the beads and I'd like to work this through with David (Viper) until we come to a conclusion on what going on.

For the layman's terms break-down, look for a new thread shortly. I'd really like to get more FOGs involved in this discussion.