That's what I'm guessing from a first quick scan, but my guess is that SOME variety of hydrogel exists that has a stronger affinity for water. It just isn't a mainstream commercial product.
The agro varieties need to "let go easily" so they don't steal water from the plants.
Probably the ideal "medium strength" desiccant is Oil Dry (oil-absorbent Bentonite clay containing montmorillonite). Dave pointed it out, maybe during a podcast, and suggested looking for it in an Auto Supplies store or that isle of a big-box store. 40 pounds for $8, and you can regenerate it at 150F!
http://garden.org/blogs/view/R...
(I'm working that blog entry up to be an article, but I need photos first.)
