Sodium bentonite swells up to 15 times its dry volume when hydrated, producing the high-viscosity, low-permeability gels required for rotary drilling fluids and borehole sealing. Calcium bentonite swells much less and is generally unsuitable for drilling-grade applications without activation (treatment with soda ash). Buyers specifying API-grade drilling bentonite should confirm the sodium content and swell index in the certificate of analysis.

Bentonite used as a fining agent in wine, juice, or edible oil processing must meet food-grade purity standards and is subject to FDA review as a food additive or GRAS substance. Importers supplying food-processing customers should obtain food-grade certificates and verify that the material complies with applicable FDA specifications. Consulting a licensed customs broker and reviewing FDA guidance is advisable before entry.