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Polishing Aluminum

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Posted by Jarvis Krumbein on August 30, 2003 04:57:01 UTC

The coating doesn't need polishing, the glass does. When an aluminum coat is evaporated onto glass, the aluminum is only molecules thick and its surface is an accurate copy of the glass underneath. If the coating is hazy, then the glass underneath is not fully polished (at least if the coating was done by a reputable outfit. This is a very common problem with amatuer made mirrors, especially the first. It's not uncommon for the glass to not be fully polished. Usually, the center is fully polished and an outer area is not. If this is the case,mask off the outer unpolished area and use the mirror as is until you are ready to tackle a repolish and refiguring job. If hazy all over, the only solution is to finish the polish and refigure the parabolic shape to the mirror. If youexamine the glass before the aluminum coat is put on, it is not always easy to tell that the glass is not fully polished. Use a very bright concentrated light, such as a laser pointer, and if you can easily see the light on the surface of the glass, it's not fully polished. I repeat the first part, the aluminum only shows what's actually on the glass surface.

Jarvis Krumbein

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