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!
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.