How to Make a 12-Inch Telescope Mirror

Make the Grinding Tool

• 1

  Set the compass to a radius of 5.7 inches. This measurement is 95 percent of the radius of the mirror you will be making. Use the compass to trace a circle around the sheet of tile. The middle tile on the sheet should be slightly left of the center of the circle.

• 2

  Cut out the circle of tiles with the tile cutters. Some tiles on the edges may be cut in half; remove these tiles altogether with the tile cutter.

• 3

  Use the sharpening stone to make a bevel flush with the edge of the mirror blank.

• 4

  Put the mirror blank on your work surface so that the side you will be shaping faces up. Cut the window blind so that it is just large enough to go around the mirror blank. Wrap the window blind around the mirror blank. Tape the blind together with duct tape. You have now made a mold for making a tile tool.

• 5

  Center the circle of tiles on the mirror blank.

• 6

  Put on protective latex gloves and a mask, and mix up 25 lbs. of dental stone in a bucket.

• 7

  Pour the dental stone into the center of the tiles. Tap the window blind to bring any bubbles to the surface. Smooth the top of the poured stone with your gloved hands.

• 8

  Wait 20 minutes for the dental stone to set. Remove the window blind. You now have a grinding tool made from the tiles and dental stone.

• 9

  Separate the tool from the mirror. If you have difficulty separating them, insert a utility knife in between the tiles and the edge of the mirror to break the seal between them.

Make the Mirror

• 10

  Place the mirror blank into the cut-out area of the countertop that was meant for the sink. Put glass clamps in the holes meant for the faucets and clamp them to the mirror blank.

• 11

  Wet the sharpening stone with water. Bevel the edge of the mirror blank at a 45 degree angle.

• 12

  Add 1/2 tsp. ofPgrit to the surface of your grinding tool. Sprinkle the tool with water.

• 13

  Put the edge of the tool on the center of the mirror. Move the tool forward over 1/6 of the length of the mirror, then move it backwards to where you started. Every six or seven strokes, rotate the mirror clockwise a random number of degrees and rotate the tool counterclockwise a random number of degrees. When you stop hearing a grinding noise, add more grit and sprinkle the tool with water before continuing to grind the mirror. When the center of the mirror appears to be sagging but the edges appear untouched, move the tool edge over the center of the mirror. Continue grinding until the entire mirror has a circular shape.

• 14

  Rinse the mirror with clear water and dry with a clean, soft cloth. Clean the grinding tool with a scrub brush and dry it with a different cloth. Prepare the tool withxgrit and sprinkle with water. Grind slowly so that the surface of the mirror will be of uniform smoothness. Continue grinding until the mirror appears uniformly smooth. This will take several hours.