From: RWolf99@aol.com
Message-ID: <149.b756da7.29cb6925@aol.com>
Date: Thu, 21 Mar 2002 11:49:41 EST
Subject: Re: Reagent Grade Acetone
To: lancair.list@olsusa.com
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I'm not a chemist (and I don't like Holiday Inn Express) but I did work in a 
chem lab for a while making experimental batteries for electric cars.  We 
used acetone rather freely, and I'm pretty sure that acetone gives me a 
powerful headache.  (MC on the other hand, just gives me liver 
cancer....which I don't really have because I treat MC like it's poison.)

Anyway, I use MC exclusively because it's a superior solvent.  Just smear 
some schmutz on a piece of anything with a shiny surface, or glass, anything 
on which you can plainly see if the residue is there.  Squirt some acetone on 
it and watch the schmutz kinda dissolve -- squirt some MC on it instead and 
watch the schmutz just instantly disappear.  Like David Jones, I sometimes am 
frustrated by people ignoring my advice, but on this issue my first-hand 
experience confirms his wisdom.

I've discovered that some shops don't use MC because of the OSHA regulations 
for personnel protection required for MC that aren't required for acetone, or 
so they tell me.  Kinda makes you wonder how safe it is to use at home, eh?  
And if you read the MSDS you'll see that the TLV (threshhold limit value -- 
maximum concentration allowed for 8 hours continuous exposure) is exceeded by 
one drop evaporating in a standard size garage.  But I don't have MC floating 
around my shop for eight hours per day.  I only use it just before a layup, 
and then I air out the shop.

How do I, a non-expert and non-chemist, protect myself?  I have a small 
bottle of the stuff, so that the risk of spilling is significantly reduced.  
I refill the small bottle from a larger bottle when I need to.  I refill the 
larger bottle from my 5 gallon can outdoors -- I spill a lot here.  (It kills 
grass, by the way, but that's another story...)  I try real hard not to 
breathe the vapors when I'm wiping things down or refilling bottles, and I 
open the garage doors when I am wiping.  I throw the dirty-but-still-wet rags 
outside to dry.  I wear the heavy gloves (butyl) for wiping.  Even though 
these gloves are too heavy for precise work, they're okay for wiping.  I then 
don't touch the parts unless I'm wearing latex gloves.  It's not as much 
protection as the chemical fume hoods in the chem labs, but it seems to be 
working for me.  No liver cancer yet (I hope....)

I prepare surfaces a little differently than Curtis.  I agree with him that 
roughing up a surface within an hour of bonding is good -- and my chemist 
friends tell me that the surface is more "chemically active" that way and you 
get a better bond.  The difference is that I wipe off the dust -- and any 
residue that I've inadvertently applied with the sandpaper -- with MC before 
bonding.  Also, I clean before sanding as well because, as the manual says, 
it's kinda dumb to grind any dirt or oil into the surface with sandpaper -- 
better to clean it off first.

With respect to Steve Colwell's comments -- you can definitely get solvent 
soaked into a honeycomb or foam core, and that's stuff's gonna come out 
somewhere.  Better to wipe down those surfaces some time prior to bonding to 
give time for evaporation and vapor escape, and a heat gun definitely helps 
here.

I'm told by an ex-Lancair employee (from the Philippine factory) that they 
did run adhesion tests with acetone-prepared surfaces, and that adhesion was 
improved by letting an acetone-prepared surface "dry" overnight.  Take that 
as an unconfirmed rumor.  

I know a lot of airplanes have been successfully built with acetone as a 
cleaner, but I'm sticking with MC.

If you have problems finding MC, call the oil companies (like Shell Oil, for 
instance).  Not the gas station at the corner, but in the Yellow Pages -- the 
distributors.  It turns out that MC is a by-product of the petrochemical 
industry, or is used meaviny by them, or something, because you can get 5 
gallons for around $35, and if you buy gas chromatograph grade stuff from, 
say, Fisher Scientific it costs about $80 per gallon.

(Marv has a list of MC suppliers somewhere on his website, by the way.)

- Rob Wolf
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