Abstract: A pH-indicating material capable of undergoing a clearly visually detectable color transition at a desired pH, e.g., at a pH at or below about 5.6 and/or at a pH at or above about 7.6. When the pH-indicating material is wetted on its surface with liquid animal dross, particularly animal urine, such as cat urine, the pH-indicating material will undergo a clearly visible color transition at a urine-problematic pH, e.g., acidic or alkaline. The pH-indicating material is maintained on an inert carrier, separate from the cat litter material itself, so that the cat litter material does not chemically interfere with the urine pH-induced color transition provided by the dye(s) in the coating material, and so that the color transition is an exclusive result of the pH of the contacting animal urine, without pH interference from the litter material.