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Our physics department has recently acquired a 26 inch diameter silver telescope mirror that is quite a bit tarnished. Would attempting a light bit of polish be possible before we try to resurface the entire thing? It may need polished and resurfaced anyway, but I'd like to begin by at least getting a light bucket out of it first because, as with any large scale project, showing that we can at least operate it will help get the funds we need for an observatory project as time goes one. Thanks!

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  • $\begingroup$ I guess what I'm asking is, can we clean it up to get it working with some tarnish remover and a good cleaning, then we'll worry about funding to have it sent in and resurfaced as we don't have a vacuum chamber large enough to re-alumize the mirror. I'm currently tracking down the age and history, it does seem quite old. $\endgroup$ – Ryan Jul 26 '18 at 19:14
  • $\begingroup$ You can remove Aluminium with dilute NaOH without damaging the blank - then you need to recoat. $\endgroup$ – Martin Beckett Jul 26 '18 at 20:39
  • $\begingroup$ The problem, as always, comes down to funding. I'd like to clean it as best as I can and get a decent light bucket out of it, then ask for funding for a professional re-coating, any tips for cleaning it up a bit? $\endgroup$ – Ryan Jul 27 '18 at 0:09
  • $\begingroup$ You might want to look at this restoration info and this funding website. $\endgroup$ – Rob Jul 27 '18 at 1:23
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Very old silver should be black or close to it from sulfide. I expect they are aluminized . For a critical application , if washing is not good enough, you need a professional to polish or re-coat. The size also calls for a pro. I am familiar with polishing metallographic samples but they are typically < 1 in. diameter : Even going to 2 in. diameter caused problems.

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