OK, so now you folks have gotten me confused.
I tried to understand the hysteresis curve as mentioned above, and assuming your talking about "matric potential hysteresis". My understanding is it shows errors or varience in the potential water content, IE: saturation could be between x% and y% making it hard to measure volumetric water content.
So how does the inability to accurately measure the water content in the beads relate to their abilty to maintain a specific RH?
I wish you hadn't brought this up, I now have more questions than I need about beads. I was happy just knowing they worked.
~Vitis