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Requirement is simple(!) - I have 30mm silvered glass balls that are originally Christmas tree decoration that I want to use in a very unconventional manner in a physics experiment. As far as I can tell the Aluminium is external. The balls are exceptionally delicate and the glass probably somewhat stressed i.e. they break easily if scratched.

So, would dilute NaOH be suitable or is there a better solution? Another requirement is that ideally the treatment does not raise the surface energy of the glass

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    $\begingroup$ just for the beauty i would recommend mercury ;) $\endgroup$
    – mcocdawc
    Commented Oct 6, 2015 at 15:54
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    $\begingroup$ The classic etch for aluminum in the semiconductor world is 25:5:1 phosphouric-acetic-nitric (for faster etching 25:5:5 can be done). This does not negatively impact field oxides for Si devices, if you take that as any indication of 'surface energy'. $\endgroup$
    – Jon Custer
    Commented Oct 6, 2015 at 18:14
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    $\begingroup$ Diluted (5-10%) HCl, HNO3 and H2SO4 should work equally well. $\endgroup$
    – permeakra
    Commented Jun 22, 2016 at 14:56
  • $\begingroup$ Acid, or just throw it away. Neither are valuable enough to risk injury. $\endgroup$
    – DrAzulene
    Commented Jul 5, 2016 at 18:11

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Heating the bulb in a dilute NaOH solution would probably work, yes. Something that might be more 'interesting', and potentially safer (with less hydrogen) though, is to acquire a bit of gallium.

Gallium infiltration is a really fascinating phenomenon. Simply melt a little bit of gallium and dunk your bulb in it, and watch as the aluminum becomes as soft as wet tissue paper. Gallium also melts at a temperature very slightly above that of room temperature, meaning that the the chance of the glass bulb cracking because of heating would be very minimal.

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