There is no PG (Propylene Glycol), salts, or silica in HCM beads. HCM Beads work using the simple principle of equilibrium. They have a much higher affinity for gathering and releasing water than silica beads; the construction of HCM beads allows for a far greater reservoir of water to be made available for use in a humidor.
In a sealed humidor, they are by far the fastest and easiest way to control humidity. They also scavenge and hold free ammonia. The physical properties and principles behind HCM beads allow them to maintain the RH in a humidor.
Propylene glycol is hygroscopic, but only so far as its volumetric nature allows it to gather water, and the capacity of PG to absorb water is very minimal when compared to HCM beads. From an article on Liquid Desiccant Drying Systems
Glycols function much like hygroscopic salts, but require higher concentrations to achieve equilibrium and may also evaporate. Glycol concentrations may be as high as twice those of hygroscopic salts, requiring a significantly larger amount of solution to work as a desiccant. Due to the potential for evaporation, the solution may need to be periodically replaced...
When PG is combined with water or SAP (Super Absorbent Polymer), its hygroscopic properties are instantly defeated because you have just created a saturated solution. Saturated as in "I can no longer gather water because I am saturated, thus PG is no longer hygroscopic until the absorbed water has been reduced below its capacity to hold water.
Mixed with water or SAP, PG will only release water at a rate equal to 70% RH. That is good because in a saturated solution you can control the release of water, holding it at 70%. So in this instance, you have got a great opportunity to use it where a lot of water is needed to maintain a humidor. This makes PG and SAP a good choice for very dry places or leaky humidors.
However, if your humidor sits in an area where the ambient RH is higher than 70%, the humidor is going to assume the higher ambient over time, whether it be through frequent opening or an inherently leaky humidor. That is the problem with PG and SAP. PG is hygroscopic except when it is already saturated. Even when it is not saturated, its ability to soak up water is nominal at best.
A desiccant gathers water until it reaches equilibrium with the ambient environment. If the beads are treated with a PG solution those beads will release water until they have achieved 70% RH.
Untreated beads will try to gather water until they reach their equilibrium (whatever that may be) regardless of the ambient RH. This means you have untreated beads trying to absorb water and PG treated beads trying to give up water. This results in a medium that will release water and absorb water, that has little to do with the hygroscopic nature of PG. The result is beads "battling" each other.
This does allow some control over RH by both gathering and releasing water at a particular RH. This is easily put out of balance by overwatering the beads. Once the beads are saturated, you have just turned them into the same thing as a pg/water/sap medium.
Inversely, we can keep the beads totally dry and they will simply adsorb water until they have reached equilibrium, which would be the 70% that the PG dictates. Then they will need to be dried out to continue absorbing water.
There is one thing that no humidification product -- HCM beads, silica or SAP can defeat, and that is a leaky humidor. Whether because it is warped, has a poor seal around the lid or door, leaky seals around glass, or it is a wine cooler and the drain is not plugged.
A person is far better off with a Rubbermaid™ container or a Ziploc™ bag than a leaky humidor. The biggest problem is that many commercially available humidors leak. The good thing is most can be fixed!
An 8 oz bag can handle a 2.5 cubic foot (4,320 cubic inch) humidor; that is approximately 12" x 18" x 20". Most use an 8 oz bag for a 50 quart coolidor although it is twice what is needed. Three 8 oz bags seems to be the perfect amount for Vinotemps or Edgestars.
You get a bag with a measured amount of HCM beads. The bags are permanent and made of 100% fusible nylon knit interlacing that is very sheer and allows for excellent transfer of humidity between the beads and the air in your humidor. They will last a lifetime with proper care and work at least 800% better than any other passive humidification product available. They do not break, turn color, collect odors or wear out. They also grab and hold any free ammonia that comes off of your cigars -- especially important for Coolidors (that do not have wood to absorb the ammonia) used for aging cigars.
All the bags are handmade and come in the following sizes (by weight; physical sizes may vary slightly):
One ounce of beads will easily handle 500 cubic inches (5" x 10" x 10") -- a small or medium sized cigar caddy.
We recommend that you use twice the required amount.
We sell hygrometers that can easily be calibrated to 65% RH. If you need to calibrate one yourself we recommend using the 65% Boveda pack rather than the salt test (easier to do and less mess). We also sell the 65% Boveda Packs.
Whatever RH you decide upon -- that is the RH at which to calibrate your hygrometer. A hygrometer calibrated at 75% may be accurate at or around 75%, but not quite so accurate at 65%. It is best to calibrate for your desired RH.
It takes a long time to dry out (or hydrate) cigars. Not hours or days or sometimes even weeks. It can take months. Patience is the name of the game.
The HCM beads will (in a sealed environment) absorb water vapor until they reach equilibrium with their environment. This means that if all your cigars are at 70% the beads will absorb the water vapor until they reach an RH that is equal with the cigars.
This means that they will absorb the moisture from the cigars, and the beads themselves will be at a (slightly) higher RH. You should periodically check the RH of your beads by putting them in a Ziploc™ bag with a calibrated hygrometer for a couple of hours. If the beads are too high you can put them in your refrigerator until the RH comes down to where you want it. When you take the beads out of the cold environment you need to immediately put them into a Ziploc™ bag with a hygrometer until they warm to room temperature. Otherwise water will rapidly condense from the surrounding air onto the beads -- defeating the whole drying-out process.
Never add water or wet HCM beads! If you want to increase the RH of the beads, put them in a Ziploc™, Tupperware™ or other sealed container with a damp sponge -- making sure that the sponge does not touch the beads -- and a hygrometer. Once the beads are at the desired RH, take the sponge out and seal the bag and let it sit for a time to verify that you have a stable RH.
Watersorb® is just SAP (Super Absorbent Polymer). It simply gives off and absorbs water, there is no control over RH levels. It will not absorb water from the air once it is wet either. It only works in one direction, and that is to give off water. If you hydrate WatersorbÂ® with a 50/50 PG (Propylene Gycol) solution then you can keep your RH at 70% in your humidor. You have to supply ample surface area though, and that is tough when you have a big humidor as Watersorb® will take up a lot of space.
Get a Ziploc™ bag, a screw-on bottle cap (or other small container), a small amount of regular table salt, and water.
In order to get the same humidity buffering benefit from kitty litter as from HCM beads, a person would need to use 9 to 14 pounds of kitty litter as compared to one pound of HCM beads. At $50 for a pound of HCM beads and $28 for 14 pounds of kitty litter, it appears at first to be a "value". The problem is, in order for the Kitty litter to work as well as one pound of HCM beads, it needs to be arranged so as to provide 910 square inches of surface area as opposed to 65 square inches of surface area for HCM beads. Are you willing to spare that kind of space in your humidor?
Even at that rate, the kitty litter is far slower reactively than are HCM beads. They can handle the buffering and provide the volume needed, but they take much longer to recover the RH of the conditioned space.