It doesn't have to be clear nail polish, you can use fun fashion colors if you prefer.<br><br>It is oxidation. The nail polish puts a barrier between the magneiusm and the oxygen in the air. Once the oxygen cannot get to the MFS, then you have stopped the oxidation and you won't get the sandy coating. You could also use paint or laquer. Remember that whatever you do use, will have to be scrapped through to get to the MFS when you use it. <br><br>You might want to keep a coarse hack saw blade on the bead chain to scrape the block to make shavings and the striker to make sparks. It will help protect your knife. You can break a full size blade into shorter lengths so it will be the same size as the MFS.