A sharpening stone is essential to keeping your knives sharp. To keep your sharpening stone in good shape, you must clean it adequately after every use. The short investment of time it takes to clean the stone will pay off in the long run, as your stone will stay in top shape, enabling you to keep your knives in top shape as well.
Glossy gray streaks on your sharpening stone indicate debris buildup. What you use to clean the stone depends on the type of stone you use and what you use while sharpening your knife. Make sure to put a towel under your sharpening stone during the cleaning process to catch excess particles.
Decide what you will use to clean your sharpening stone. You can use honing oil to sharpen your knife and to clean the stone. Honing oil provides lubrication for sharpening your stone, reduces friction and keeps metallic particles from embedding into the sharpening stone. To clean your stone, apply a small amount of oil, and rub it in a circular motion down the length of the stone. You'll see metal flecks rise up from the pores, and as this happens, wipe the stone with a rag or paper towel. Rinse the stone under running water and then dry it with a paper towel or rag.
If you use a water-based honing oil, clean the sharpening stone with warm, soapy water. You can use an old toothbrush or a green scrubbing sponge to scrub the stone clean. Use the same motion lengthwise, circular motion.