^ I thought the same thing when thinking about it yesterday but I wasn't gonna say anything, cuz it seemed more than just a little bit weird. Great minds, eh?

To answer your question, no it doesn't precipitate the tannins. Bentonite or activated carbon will ADsorb the tannins and other insolubles. Adsorption is not absorption. Adsorption is a surface based bonding process whereas absorption occurs through permeation or solvation.

Perfect

I bow before your incredible knowledge.

My partner has cat litter made of bentonite, I wonder if that would work (unused, of course).

Blessings
~ND

Yep, just make sure it's only bentonite and doesn't have silica gel or anti caking agents. It it does, soak it in cool water then filter to collect the bentonite alone.

I know this isn't vegan but I have a question.

My original comment I thought egg shell was used instead of egg whites, could powdered egg shells be used in the same fashion as bentonite? They do have a stain/dye absorbing ability in the presence of tannin rich foods, red wine and coffee for example. If you wanted to keep things food grade at least.

They, very possibly, could. Only way to know for sure is to do an experiment.