what makes clumping cat litter clump?

Clumping cat litter contains bentonite clay, which swells and forms clumps upon contact with moisture.

Clumping cat litter clumps because it contains bentonite clay, a naturally absorbent mineral that expands when it comes into contact with liquids. This swelling action binds the wet particles together into a solid mass, which makes it easy to scoop out waste without replacing the entire litter box contents. Bentonite clay is favored for its superior clumping ability, odor control, and convenience in daily cleaning. Some newer clumping litters use alternative ingredients like corn, wheat, or tofu, which also clump but may not form as hard or fast-binding clumps as bentonite does. Regardless of the material, the ability to clump improves hygiene and user convenience.