[SeanGAR]

Pretty much anything will absorb and release water, as will kitty litter and that old wool sweater you received for Christmas in 1986. The key is getting something with enough moisture absorptive capacity so you don't need to recharge once a day and the proper hysteresis curve so you maintain the humidity you seek. I use and recommend beads, the humi care jars get moldy on me after a few months unless I spike them with benzoate or something.