From: Jeepstuf@aol.com
Date: Thu Aug 22 2002 - 21:59:10 PDT
J. Lee, I think that the key to dry vs gloss is the paint system, not the
gun. With a flat finish, a thinner like acetone (highly volatile and fast
flashing) is perfect; you just don't want paint to flow much which allows the
flattenig agents to be prominent on the surface. I doubt if you could find
acetone in a commercial body shop (except for fiberglass work) because (where
acrylic enamel is concerned) a painter will carefully choose a REDUCER (which
is blended for the paint sytem) that works with the ambient temperature to
achieve a particular result. In other words, he (or she (PC)) will pick a
FAST, SLOW or MEDIUM reducer to get a good flowout and still dry as quickly
as possible. I don't know if you can tell, but I'm not a big fan of acrylic
enamel. I used to spray gallons of it, with hardener and from good brands but
it's just not a patch on the ass of a modern urethane type paint system. And
before anybody protests that "the Army uses enamel," well thats bunk. Just
'cause you can get surplus enamel doesn't prove their point. The Army paints
crates too. "CARC" is a urethane, catalyzed paint. And I work with a Gov't
contractor painting misc veh's (mostly M-35s,) after sandblasting, with good
old 2-part paint. Now I'll try to calm down....
When I'm painting an HMV, I have a paint store mix a color to match a sample,
whether it be a spray-can sample from one of the suppliers or a carefully
uncovered bit of OEM paint from a part or vehicle.
As for the compressor, try to locate a tank from a retired compressor and put
it in series with a hose. Your unit can work longer, fill it up and you'll
get some more spraying time.
Static grounding is out of my area- down here in the south, our high humidity
makes static a rare problem. As for dirt, do you wet down the area where you
spray? Go ahead and hose it down, just don't wet the vehicle. and if you do,
just hose blow it off with the air hose. Oh, and try the grounding method
too..
Paul, hmmmm, rust converters...
Type one, the stuff sold on TV and at the hardware store. They "convert" the
rust and leave a plastic-like film that as the instructions say, can't be
sanded. This is because the biggest thing they do is seal out water. This is
another item that will not be found in a business that has to guarantee their
work.
Type 2, Metal Cleaner & Conversion Coating. These will vary among brands
(like PPG, Dupont, Napa/Sher-Wms, Glassurit, Sikkens etc etc) but usually
work as a pair. Notable example is Metal-Prep which I don't use but friends
do; I believe that it does both jobs in one for big sloppy industrial work.
MC and CC contain no surface fillers (they are an almost invisible film),
they are only used on exterior surfaces (you can't guarantee that
nuetralization takes place if it pools) and must be coated with an epoxy
primer and a top coat. They help stop corrosion at chips and nicks. Metal
cleaner cleans and etches the surface, will disolve light surface rust and is
phosphoric acid based. It must be rinsed off and dried in most cases. Then
the conversion coating (also phosphoric acid based) is applied which produces
a zinc phosphate coating (which can act like a sacrificial metal like zinc
galvanizing.) These products must be washed off unless they self-nutralize
like SELF ETCHING PRIMER which I'll soon get to. but one last thing. you
can't leave conversion coating where plastic filler will be applied. In those
cases, a urethane or epoxy primer must be applied and an appropriate filler
used.The conversion coating may also include some detergent for final
cleaning; rinse it all off! An alternative to the MC & CC process is Self
Etching Primer, it's all in one and also has phos. acid so it must be used
sparingly in enclosed spaces (like pillars and hat channels.) It shouldn't be
used under filler. grind it away, fill, sand & prime with epoxy or urethane
and featheredge, covering all bare metal.
Oh, and before bodyworking and again before painting, a good habit is to wash
/ scrub everything with a Scotchbrite (3M) type pad and a cleanser like
Comet. This will get rid of dirt and oils etc and also scuff the surface to
help ensure adhesion. Then use a tack rag for dust before painting.
I'm going to rinse off my gun now...
WesG
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