[shilala]

They're made of a semi-permeable osmotic membrane that's tough as nails. You should be able to rehydrate them for years, as Adam has already proven.
I'm not so sure all the ink will stay intact, not that it matters, I was just wondering. A guy could pretty easily gather up the membrane and salts to make these himself, were he so inclined.
When I developed the HCM beads I also created a salt permeated SAP that I intended to offer as a recharging device, but couldn't find a readily available PVC container that would keep the salt-creep in check. If you've ever had a saltwater fish tank, you're familiar with salt creep. Salt will climb right out of any kind of container when it's in solution, given enough time. It makes a huge mess. PVC is the only surface material that salt can't climb (that I know of). I made containers of PVC pipe fittings and screw caps, but they looked like crap. Plus the salt would crust on the surface of the SAP and required regular stirring.
The whole idea was sound, but the implementation sucked and I soon gave up on it.