Bentonite swells when it’s exposed to moisture. When it dries, does it shrink?
Unless it is non-swelling bentonite.
The swelling type of bentonite is sodium bentonite, which expands when it’s wet. It can absorb several hundred percent of its dry weight in water and is used mostly in the oil and gas industries.
The non-swelling type of bentonie is calcium bentonite and is sold in the (alternative) health market for its purported cleansing properties. One ingests it, where it absorbs impurities and is then excreted. Supposedly. Theoretically.
One would not want to ingest sodium bentonite. And, quite frankly, I’m not sure one would want to ingest calcium bentonite either. 
We used sodium bentonite in the oil and gas industries in Texas back in the '70s when I was involved in those industries in Kingsville, Corpus Christi, and Houston.
For more information: Bentonite
Thanks Russel
Other than using it for ponds for what other applications would you want it?
It does work well for cleansing. It’s very similar to activated charcoal in that respect. It ADSORBS, not ABSORBS. It’s awesome stuff with poisons in the body.
There are indeed two types of bentonite, but most people think of the processed swelling type of bentonite which is essentially from mined montmorillonite clay. It’s commonly used as a slurry for foundations and as a drilling mud for soil borings around my neck of the woods (no oil wells here … lol).
You can ad chemicals to change/limit some of the properties, but if it swells when it gets wet it will shrink when it dries. Mother Nature wins again … 
Where’s Father Nature? Out drinking and fishing with his buddies? :margarit:
I always wondered about that myself … maybe you solved the mystery …
Hi. Robert;
No oil wells around here either.
The only use I have seen Betonite used is for sealing water well holes just prior to setting the steel casing in unstable grounds.
Marcel 