Message-ID: <001301bf1fb0$c8617ac0$93818ed1@pavilion>
From: "J. N. Cameron" <CIC@centurytel.net>
To: "Lancair List" <lancair.list@olsusa.com>
Subject: Plexiglass and solvents
Date: Tue, 26 Oct 1999 07:51:06 -0500
Mime-Version: 1.0

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Regarding the cleaning of plexiglass with solvents, the best rule is don't.
Ever.  After 25 years of working with acrylics, I can say that the only
solvent I have found that does not seem to have any long-term effects is 95%
ethanol.  [The 100% is usally not available, and normally has traces of
benzene in it.]  Almost any other solvent will weaken the plexiglass and
lead to crazing over time.  I've known some machine shops that use kerosene
as a lubricant in machining operations, but my experience with it is that it
will cause crazing at some later time.  I would definitely steer away from
WD-40, and although I don't have any experience with Prep-Sol, if it's a
petroleum-based solvent it is probably not a good idea for plexi.  For
lubricant in machining operations, I use water with a little liquid dish
detergent added.

Crazing is always a problem with long-term plexi installations.  It can be
relieved a great deal by proper annealing of the parts, but most of us don't
have ovens large enough for things like windows, and don't have the proper
temp control.  [For 1/4" sheet, about 1 hr at 75 degrees C, followed by a
long, slow cool is about right.]  Crazing is due to unrelieved stresses in
the acrylic, which are much worse with extruded parts, and also worse with
"brand X" acrylic.  If you buy plexi, always make sure you get a brand name
like Plexiglass G -- lots of places sell Mexican or Asian import stuff that
has a lot of styrene and much worse mechanical properties.  Solvents seem to
aggravate the stresses, or perhaps accelerate the breakdown that leads to
crazing.

I like Brent's suggestion about the beer.  Also the tape transfer thing.
All non-destructive.  You might also try warm water and liquid dish
detergent; this won't work quickly, but may soften it up enough to do the
job.

Jim Cameron   (once & future) ES builder

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