Clarification on beads, KL and SAP

Two points from a very informative earlier thread that I want clarification:

Originally Posted by shilala

I just read what I wrote, and left out a biggie.
"Propylene/water hydrated SAP doesn't adsorb water" is a large point.
If for some reason the ambient RH around a humi is greater than 70%, there's great potential for problems, especially if a humi is leaky.
If someone lived in Arizona or the desert or up in Siberia, it's an excellent choice because those humis require a lot of available water.

How does PG not absorb water? PG is hygroscopic and by definition will absorb excess water out of the atmosphere until equilibrium is reached. Part of what makes PG/water solution so effective is the vapor pressure lowering (of water) effect of PG. At various concentrations around 50% the vapor pressure of water is kept around 70% RH and vapor pressure of PG almost negligible at room temperature (<1%). The SAP acts as a medium to hold the solution similar to foam but one could just as simply leave a cup of PG in a humidor and achieve the same effect as beads. Is it the SAP itself that prevents absorption? As stated above, the advantage of PG/water in SAP is the amount of water that the crystals have. In environments in which the atmospheric RH is significantly less than the humidor and there is some leak, SAP has advantages over beads in providing larger reservoirs of water to release.

Originally Posted by bobarian

Kitty litter will absorb moisture(humidity) that is what they were designed to do. But they WILL NOT regulate or release moisture at a set level. Though they are both the same product chemically. Kitty litter has not been treated to regulate at a specific RH. I believe kitty litter will work well in high humidity areas, but out here in Cali. Heartfelt beads are the best way to go.

I have seen this statement frequently on the forums, that KL will not release water. Why is this so? KL is silica gel and all silica gels are hygroscopic. I will concede the point that plain gel (which is probably what KL is composed) has an M(H) value much lower than treated Heartfelt beads at 70% RH. But nevertheless KL will release as well as absorb water. The key point is finding a buffering agent with the highest M(H) value at the desired RH. Artsorb for example has a very high buffering capacity at RH > 70%. I read with great interest Shilala's experiment with KL and treated beads the amount of each needed. In essence he has derived experimentally rather than mathematically a comparison of M(H) of various substances at 70% RH. However it is still possible to use KL or any silica gel for that matter to maintain a set RH via pre-conditioning. The only question, as Shilala so eloquently answered in his experiment, is how much of each agent is needed and at what price/performance ratio.