Dead skin will build up in the pores of the stone as you use it, so you'll want to clean the stone after use. Use a scrub brush to scrub the stone while holding it under running water. Add a bit of soap to help clean the stone completely. This way  your stone will be clean and ready to use next time you need it. Set the pumice stone in a dry place so that it doesn't stay damp in between uses. Some pumice stones come with a string attached that allows you to hang the stone to dry. If you let the stone stay wet, bacteria could grow in the pores, making it unsafe to use. Every once in a while, you'll want to give the stone a deep cleaning to make sure it isn't harboring bacteria. Bring a small pot of water to a full boil, drop in the stone, and boil it for five minutes. Use tongs to remove the stone from the water and allow it to dry completely before storing.  If you use the stone frequently, boil it every two weeks to ensure it stays clean. If you've used the stone on a dirty surface, you can add a capful of bleach to the water to be certain all bacteria get killed. Pumice is a soft stone that will eventually wear away after you've used it for awhile. When it gets too small to handle easily, or the surface becomes too smooth to be effective, go ahead and spring for a new one. Pumice stones are inexpensive and can be found at any store that sells beauty supplies.

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Write a summary of the previous text in Vietnamese:
Cọ viên đá sau khi sử dụng. Để đá bọt khô hoàn toàn. Đun sôi đá bọt nếu cần thiết. Thay thế khi đá bọt mòn dần.