New? RH question

[Powderfinger]

If I had a air tight non-permiable container at 70 degrees temp, with a properly calibrated hygrometer inside the container reading 70% humidity, and I dropped the temp. to 50 degrees would or should the RH change? If the answer is yes, is there a temp/RH compensation chart?


Rich

[ashauler]

I think yes the rh goes down if temp goes down. I don't know of any chart.

[spiffykyle]

Yes, the RH is dependent on temperature...and pressure.

Basically, in a closed system like you are describing, with a set amount of water in the air, if the temperature drops, the RH will rise.

Do a search for Relative Humidity on wikipedia and you should find a decent explanation. However there are way to many environmental factors involved to give you a simple RH vs Temp chart, like air pressure and vapor pressure. Remember that in a sealed system, if the temperature changes and the volume doesn't, then the pressure will also change.

Why do you ask?

spiffy

[ashauler]

Yes, the RH is dependent on temperature...and pressure.

Basically, in a closed system like you are describing, with a set amount of water in the air, if the temperature drops, the RH will rise.

Do a search for Relative Humidity on wikipedia and you should find a decent explanation. However there are way to many environmental factors involved to give you a simple RH vs Temp chart, like air pressure and vapor pressure. Remember that in a sealed system, if the temperature changes and the volume doesn't, then the pressure will also change.

Why do you ask?

spiffy

Wow, was I wrong ......I thought colder air had less ability to hold moisture and therefore the rh would drop at lower temps.......hmm, off to wikipedia I go.

[Powderfinger]

The reason I ask is because I am still struggling to understand what is going on with my hygrometers. Someone suggested doing the salt test in a clear fliptop lucite airtight container. I got one of these at Walmart, and did a salt test with my new calibratable digital hygrometer. After it seemed to equalize at 68% humidity at 68 degrees temp. I always thought that the colder at container got the less humidity their would be. This I thought was why they do not recomend putting cigars in the fridge. I was wondering if the fact that being at 68 degrees temp was changing the RH reading. I will now try the Humidipak one-step calibration kit to see what that reads. I am just concerned that if it reads lets say 72% RH at 68 degrees temp, am I really getting true accuracy if I adjust the hygrometer to 75 % RH


Thanks Rich

[nhcigarfan]

I used to be hung up on RH, trying to keep it dialed in,checking it daily, etc., but it's a waste of time. I really wouldn't worry about it. Anything between 55% and 70% is fine. I like around 60%.

[spiffykyle]

The reason I ask is because I am still struggling to understand what is going on with my hygrometers. Someone suggested doing the salt test in a clear fliptop lucite airtight container. I got one of these at Walmart, and did a salt test with my new calibratable digital hygrometer. After it seemed to equalize at 68% humidity at 68 degrees temp. I always thought that the colder at container got the less humidity their would be. This I thought was why they do not recomend putting cigars in the fridge. I was wondering if the fact that being at 68 degrees temp was changing the RH reading. I will now try the Humidipak one-step calibration kit to see what that reads. I am just concerned that if it reads lets say 72% RH at 68 degrees temp, am I really getting true accuracy if I adjust the hygrometer to 75 % RH


Thanks Rich

You are thinking actual humidity, or absolute humidity, instead of Relative Humidity (RH). The RH basically dictates how much water can be released from and absorbed into the air. Which is why the RH adjusts with temperature. Your hygrometer reads RH and temp. In terms of how "hydrated" your cigars will get, 70% RH is the same at any temperature. So if your hygro reads 70% at 68° and 70% at 72°, then your humidification system is doing its job, and you have nothing to worry about. This is why beads are great since they can absorb extra humidity if the temp drops, and the re-release it back into the humidor when the temp comes back up.

To answer your question ahauler, your are kind of correct. The colder air doesn't need as much water to be "hydrated", which is why in a closed, sealed system, with a constant amount of water in the air, as the temp drops the RH increases. It needs less water to have the same RH as a system at a warmer temp.

spiffy