We've been using indicating silica gel loose beads that we got from https://www.silicagel.com.au/silica-gel-beads-loose/
. But that was before we knew about those cheaper kitty litter products (we don't have a cat). I've now tried a bentonite kitty litter. It needs to be activated in the oven before use as it comes in a paper bag and has been sitting around absorbing the ambient moisture in the shop and in transit. I used the same time and temp as I'd do for silica gel and that seemed to work.
When I use silica gel I've found that unless the seed is already fairly dry I need about the same volume of silica gel as seeds and the smallest container I can get them both into and then it takes about a week to stabilise the moisture between absorbent silica gel and the see.ds. I haven't done enough trials with the bentonite yet but I expect it will be less efficient so I might need more bentonite to seeds.
The down side with the bentonite is that it doesn't tell you when it has absorbed as much moisture as it can and needs to be reactivated. That is a big advantage with the indicating silica gel. You can easily see when it has become ineffective as the colour of the beads changes.
I'm using 6 spot humidity indicator cards inside the jars with the seeds and absorbers so I can see when the moisture level stops changing and have a rough idea of how dry the seeds are - https://www.silicagel.com.au/categories ... tor-Cards/