Polishing and Honing: The primary purpose of a 4000 grit stone is to refine the edge left by coarser stones (like 1000 or 1200 grit) and create a highly polished, very sharp edge. It's an intermediate finishing stone, often used before moving to even finer grits (e.g., 6000 or 8000 grit) for a true mirror finish.
Achieving Razor Sharpness: While not the absolute finest grit available, a 4000 grit King waterstone will produce a very sharp and smooth edge suitable for many cutting tasks, especially for kitchen knives.
Removing Scratches: It helps remove the fine scratches left by the previous, coarser sharpening stages, resulting in a cleaner and more effective cutting edge.
Maintenance: For knives that are not severely dull or damaged, a 4000 grit stone can be used for regular maintenance to keep the edge keen.
