Kilns can be classified as either intermittent or continuous, here's the difference: Intermittent kilns are loaded, fired, cooled, and unloaded in batches, such as clamp kilns, scotch kilns, and shuttle kilns. Tunnel kilns are continuous kilns. The pottery is moved through a tunnel, from preheating to cooling zones. The main difference is tunnel kilns are continuous, and other listed kilns are intermittent.