[TowerTalk] Polishing a plastic meter face to remove scratches?

[Jim Lux]

At 07:23 AM 11/12/2004 -0800, Michael Tope wrote:
>When I was in college, I worked for the physics department. We
>were fabricating adiabatic light pipes out of acrylic. Before we
>went to laser cutting, we would saw cut the acrylic, sand it, and
>then use a paste loaded with alumina particles to polish the
>edges to an optical finish. This was probably the same stuff
>that Jim W6RMK was talking about for polishing aircraft
>windshields. I think you could specify the particle size if you
>wanted to polish in steps. Wish I could remember the
>manufacturer (too many dead brain cells since then).
>
>73 de Mike, W4EF....................................

This reminds me of another way to get a very high quality polish on 
plastic: firepolishing.  Might be a bit dicey on a meter faceplate 
though!  Here's how you do it.

Polish with fine grit til the surface is smooth. Then, use a single edge 
razor blade to scrape smoother.  Then, carefully play a clean flame over 
the surface until the small remaining pits and bumps melt and merge.  Works 
really, really well on acrylic or polycarbonate edges, for instance.  Large 
surfaces are tricky.  Don't try this on styrene (ignites too easily!).  You 
need a very clean, blue flame too, or the soot will cause problems.  An 
alcohol lamp burning methanol works, as do those little butane torches with 
a flame spreader.  The ultimate clean flame is oxyhydrogen.  A hot air gun 
might work, if you have the right kind.  Some of the guys at the shop I 
used to work in were great with the hot air gun for this, but I never got 
the touch.  The butane flame was easiest for me.

Jim