How to Refinish a Telescope Mirror

Polishing

• 1

  Attach three, 1x1x6 inch wooden planks to the stool in a triangular formation, so that the mirror is held tightly in place when positioned within the triangle. Place the mirror face-up (this is the face with the reflective surface) so that the face extends 1/4 inch above the wooden planks.

• 2

  Clean the mirror with a diluted water and detergent solution (3 drops of detergent to 1 quart of water) and then position it on the stool, held in place by the three wooden planks (the mirror does not need to be dry). Wet the surface of the mirror and then sprinkle a small amount of 1500 mesh emery onto the mirror surface. Using light, circular strokes, remove the existing reflective coating. Rinse completely when finished, taking extra care to remove all emery particles from the surface of the mirror.

• 3

  Wet the surface of the mirror and apply a sprinkling of jeweler's rouge to the mirror surface. Gently, very gently, polish the surface of the entire mirror with a clean cotton rag using small circular motions. Rinse and repeat until all pits or scratches have been removed, then stop and wash the mirror surface using a dilute detergent solution. Rinse the mirror surface using distilled water and allow to completely dry and check for any residue. All traces of the jeweler's rouge must be removed

Resurfacing

• 4

  Prepare a silver solution of 22 gms Silver nitrate with 1000 c.c. of distilled water. Prepare a formaldehyde solution of 200 c.c. of formaldehyde with 800 c.c. of distilled water. This is sufficient for silvering 50 square inches of mirror (eight-inch diameter). Depending on the size of your telescope mirror, increase or decrease the amount of solution. If necessary, allow both solutions to reach room temperature.

• 5

  Combine the two solutions in a glass container large enough to hold the telescope mirror and then immediately immerse the mirror, face down, in the glass container. In three to five minutes, black particles of silver will begin to form within the solution, signaling the end of the silvering process. At this point, remove the mirror and flush the mirror surface with distilled water.

• 6

  Check the thickness and reflectivity of the silver coating. If the reflective coating is not thick enough (If it is transparent), repeat the silvering process. When finished, rinse the mirror with distilled water and allow to dry completely in an area free of dust and dirt. The mirror is ready to be reattached to the telescope and will provide many years of service.