I can't find the answer to it anywhere. I'm using PG 50/50 in my humidifiers and I assume that it is the H20 that evaporates. Does that mean I should only add H20 to recharge it or add more 50/50 PG?

No questions are dumb questions 😛

Yes, you only need to add distilled water, but need to recharge the humidifier with 50/50 every .... 1.5 months (some say 1, some say 2, so I just take the average one).

The PG solution acts as an absorbant (sp?) of excess moisture, and also as a preservative (anti-bacterial). (in case you didn't know that, but if you do, I apologize for being repetitious).

Just add distilled water ... you only need to recharge with 50/50 about once every three months.

Oro,

Welcome.

You are correct. Add distilled water, regularly, and 50/50 about every 6 mo.

Later

Dave (A.K.A. Homebrew)

While all these gentlemen are correct... Err on the side of caution. Keep adding only distilled water until the humidity doesn't stabilize well, then ad some 50/50. Could be a while before you need any.

ajeroth

From 1 month to 6 months... see the variation? I think it depends on the size of your humidor/cooler/tupperware.

All that will happen with PPG ... is that it will help regulate the humidity.

Viscosity increases and water solubility decreases with increasing molecular weight.

It makes no difference on how small or large your humidor is, as far as the PPG goes, because it will absorb excess moisture as it goes above 70% Rh, and release it as it goes below 70% Rh.

That's not to say that you won't need a larger (or more) humidifier(s) for a larger humidor ... all I'm saying is that the properties of PPG doesn't change with the size of your humidor.

In a closed system, such as a cooler or humidor, water in a container or water from a saturated sponge will evaporate until an equilibrium condition exists. That equilibrium condition, represented by the "relative humidity", is governed by the partial pressure of water vapor at a given temperature.

As we all know from experience, the partial pressure of water vapor (the relative humidity of the system) is way too high for storing cigars. When we add propylene glycol to the mix, we "interfere" with the ability of the water to evaporate from the sponge. In essence, the partial pressure of the water vapor is REDUCED by adding a material which inhibits the ability of the water vapor to evaporate.

The identity of the interfering material is really not important - it can be ethylene glycol, glycerin, or even common table salt - but the amount in the mix certainly IS important. At a 50-50 mix of propylene glycol to water, the equilibrium vapor pressure of water at 70 deg. F will yield a relative humidity of some 72% RH.

As more water tries to evaporate from the sponge, to take care of dry cigars, for example, or because the humidor is not really a truly closed system, it becomes increasingly difficult for the water to evaporate because the relative concentration of propylene glycol increases in the remaining mix. The propylene glycol is a non-volatile material and will not evaporate from the sponge. Once charged, the sponge should be replenished only with distilled water to restore the original 50-50 mix, if that is what is desired.

I prefer to keep my cigars at 67% relative humidity. To achieve this, I charge a sponge with a mixture of 58% propylene glycol and 42% water. As water evaporates from this system and the sponge struggles to raise the RH above about 64%, I add water at this time. The sponge will still feel "heavy", because it is then only loaded with PG.

Think of the amount of proylene glycol in your initial charge as a "humidistat" for your system. Here are the values to use for a given desired relative humidity, assuming a 70 deg. F storage temperature:

Desired RH %PG %H20

65 60 40

66 59 41

67 58 42

68 57 43

69 56 44

70 54 46

71 52 48

72 50 50

The astute observer will notice that the relationship between relative humidity and %PG in the system is not linear, but begins increasing sharply below about 55% PG in the system. This is why so many people struggle to get the %RH in their coolerdor down below 70%, even though they are using 50-50 mixes.

I swiped that from someone else btw..

YIKES!!!

My explaination said the same thing ... only much easier to understand ... LOL!

Thanks much guys. I feel like I know what I'm doing now.

What mrtelcom said..................