PHASE ONE - MIRROR GRINDING
1 Wash the glass backing plate in running tap water. Dry it with a clean paper towel and place it flat on another piece of clean paper towel on a clean, smooth, horizontal surface. This should be a table or a lab bench, which is at a comfortable working height for you. Wash your hands with soap and water and dry them with a towel. Seat yourselves (this is a team project) in chairs or lab stools around the table or bench.
2 Color the flat face of both mirrors with a permanent marker pen or colored grease pencil. The colored metal will show how much of the surface needs to be ground away. (When you have ground all of the color away, and the surface of the mirror is a uniform, dull gray, you will have properly removed the machine tool marks from the face of the mirror.) If you can't find a colored marker, that will be O.K. You can still judge your grinding progress by seeing if there are any shiny places left on the face of the mirror. Pick up the brown dropper bottle labeled "Aluminum Oxide Grinding Slurry." It contains a soupy, pink-colored mixture of very small particles of aluminum oxide powder suspended in water. When thoroughly mixed, this slurry is the consistency of cake batter, paint, or thick soup or cream. Shake the bottle vigorously for about a minute to mix