[rescue] Oh my gosh, an on-topic question! ;^)

[James Lockwood]

On Thu, 20 Feb 2003 vance at neurotica.com wrote:

> On Wed, 19 Feb 2003, Ron Wickersham wrote:
>
> > > -James [my personal fave is bead blasting with tiny CO2 pellets]
> >
> > which brings the question did you make your own CO2 gun or use a
> > commercial one?  i've heard that blasting with CO2 snow is the best way
> > to clean optical surfaces, so it sounds kind to surfaces.

Commercial, though I can see how one of those dry ice "sock" collectors
could be retrofitted.  You want enough gas expansion to solidify, but not
so much that your velocity drops way down.

I think that the reason it works so well is the combination of CO2 solvent
action, thermal stressing and very mild abrasion.  Neat trick.

> Be careful about accumulation of condensate.

Nitrogen or argon blanket in a glovebox, I expect.  Toss in a bunch of
Drie-Rite.  Dunk in acetone to pull surface water out, any water or ice
left will evaporate much more rapidly than straight H2O due to
azeotrope-type behaviour at relatively low vapor pressure.  Come to think
of it, as long as you're maintaining positive pressure with relatively
heavy CO2, moisture may not be much of a problem.

A big glovebox is trivial to build compared with large precision optics.

-James