A method for making a white synthetic carbide lime filler composition of calcium hydroxide and calcium carbonate, wherein the calcium carbonate is in the form of surface carbonation on the calcium hydroxide. The method can include calcining calcium carbonate, hydrating the calcined material under controlled conditions which maintain a low moisture content and fracture the hydrated material into small particles of calcium hydroxide, carbonating the small calcium hydroxide particles to create the surface carbonation of calcium carbonate, and classifying the carbonated synthetic carbide lime particles to separate off oversized particles. The method can use a combined classifying and carbonating process, and a modified classifying vessel can be provided to carry out the combined process.