Re: [ATM] Polishing NaCl IR Filters

[Jan Bentz <jbentz@inreach.com>]

Curt Diggs wrote:

>Does anyone have any information about polishing an IR filter that's made of NaCl 3mm thick? A non-ATMer friend has a work project that involves polishing the filter which apparently doesn't need to be perfectly flat, just highly polished. I thought of using CEO but have no idea what wetting agent should be used, since water is out. Any info would be appreciated.
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>  Curt Diggs
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Curt -- The short answer is anhydrous ethylene glycol with suspended 
alumina powder which Universal Photonics sells I believe.  All 
operations and storage of finished surfaces  must be done in "dry " 
rooms or where the maximum humidity can be kept below 25%.  Well below 
if possible.  You must use a respirator and surgical gloves,  not 
because its poisonous but your breath and moisture on your fingers will 
affect the surface. 
   This stuff is very weak mechanically  breaking at about 200lb/in 
versus a minimum of over 1000lb/in for glass.  It is also very thermally 
fragile.
   Your friend better start out with some extras for breakage especially 
at 3mm.  This is not a job for beginners.   Good  luck!

Jan Bentz
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