If you want to keep a double edge razor sharp, do what folks did back during the depression. In 1961 I was an apprentice in the Brooklyn Navy Yard. Many of the Journeymen Machinists I worked with had lived through the depression. Carefully lay the dulled razor blade inside of a empty drinking glass, lay your finger on the middle of the blade and swipe it back and forth so that the cutting edge rubs against the inside curve of the glass. Turn the razor blade to the other side and swipe that side too. Just remember to handle the razor blade carefully. This trick worked eighty years ago and it still works today!!