It’s strange to me that since the bentonite content is usually only 10% of a sand mix for green sand that the amount of money would be an issue here. A 25 lb bag of bentonite is maybe 25 dollars . It’s milled to the right size and is consistent . It’s intended use is to bind the sand by retaining moisture . You don’t need more than a spoonful in a small mix of sand . Why not just use what foundries use ? You’re not like outsmarting anyone by ‘this one weird trick that foundries HATE’ or even making an improvement. Cat litter is sodium bentonite but there are two different types of bentonite sold and you have no way of knowing which you’re buying with cat litter. Also they add stabilizers and fragrances that can affect the sand and cause fuming and porosity. I’m not sure why it is unpopular to use the right materials ? It seems INsANE to argue about a fact (not opinion) just to be lazy about your foundry practice . But hey if you feel better destroying a coffee grinder to make your own powdered cat litter tinfeel like you’re doing something then knock yourself out,