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Re: paint

To: british-cars@HOOSIER
Subject: Re: paint
From: Peter_Lee@FINE.MESS.CS.CMU.EDU
Date: Thu, 19 Dec 91 17:08:56 EST
Somebody mentioned something about acrylic lacquer being "old technology",
superseded by enamel-based products such as Imron.  While it is definitely
true that enamels are a more recent development than lacquers, there most
definitely is not, in my experience, a clear winner here.  Also,  I would
hardly call Imron state-of-the-art.

Each painter should examine his/her own abilities and particular application
at hand and, taking these things into account, choose the most appropriate
products to use.

Here are some points from my own limited, though fairly broad, experiences
in the past two years of painting, in which I've used the following kinds of
products/techniques:

 - single-step lacquer
 - base-coat/clear-coat lacquer
 - single-step enamel
 - urethane base-coat/clear-coat (*dangerous* stuff!)
 - lacquer base-coat/urethane clear-coat

There is a *lot* I don't know, and every good painter develops his/her own
personal favorite techniques.  Much of the following repeats what's already
been said by others.

- Lacquers are *very* easy to work with, in either the plain single-step
process or in the base-coat/clear-coat process.  Not only are mistakes often
easy to buff out, but also things like dust particles can be (mostly)
eliminated by buffing.  This doesn't work as well for enamel paints.

- There is relatively little "mess" when working with lacquers.  The
overspray is essentially a completely dry dust which can be simply swept up.
Although I wear a charcoal-filter mask when spraying lacquer, I believe it
is safe (well, without immediate bad health effects) to spray lacquer with,
say, doubled-up dust masks, as long as ventilation is good.

- With enamels and urethanes, on the other hand, the overspray is a sticky
cloud of toxic vapors.  Complete coverage of all skin and eyes is highly
recommended, and at least a charcoal-filter mask of high quality should be
worn.  A forced-ventilation system with a dedicated air pump situated far
from the exhaust area is even better.  (Many paint companies give these
set-ups away for free if you buy enough enamel paint.)  One problem with the
forced-ventilation systems, however, is that now you must worry about two
air hoses, one for the spray gun and one for the mask.

- If you're spraying enamel or urethane in your garage and your exhaust
set-up is evacuating the vapors out in the direction of your neighbor's
house, be prepared to answer his furious demands to have his windows
replaced after they get permanently fogged up with paint!  And *never*,
ever, use enamel or urethane paint in an attached garage.  You run the risk
of making your house uninhabitable for several hours or even days.  Not to
mention the possibility of poisoning people inside.

- Most standard enamel-based paints are fairly hard to work with.  Any
little slip-up, and you've got a fairly messy problem on your hands.  (A few
mistakes I've made: drop of paint onto the hood (very easy if your spray gun
doesn't seal shut very well), touching the paint with my body/hand, touching
the paint with the air hose, too much paint leading to runs/orange peel,
metallic zebra stripes (if you're working with metallic paint), dust/hair in
the paint (make sure you wear *clean* clothes and a hat, and you make a
dust-free environment), etc.)  Nothing is more depressing than having to
wipe/strip off fresh enamel from a panel and start over.

- For most colors, especially darker ones such as greens, blues, and reds, I
think that lacquers have the potential to look much better than any enamel
that I've seen.  This also goes for gloss black and complex metallics and
pearls.  In lighter colors such as french blue, white, english cream,
pimento, etc., the enamels are quite respectable, but still not quite up to
the gloss and depth of lacquer.  The enamels produce a very deep, rich, and
durable shine, but they lack the mirror-smooth gloss of a good lacquer job. 
The difference is sort of like the difference between an unwaxed,
unpolished, but very clean car, and a freshly waxed and polished car. 
Fairly subtle difference, I suppose, but definitely a real difference.

- The key word here is *potential* --- a lacquer has *lots* of potential,
but it takes a *lot* of work to achieve this.  Serious hot-rodders will take
as much as 2 weeks to do their color coats, sometimes with a dozen cycles of
color-coat/wet-sand.  A more "standard" job would use maybe 4 coats of color
(with suitable time for the paint to "flash" in between each), followed by
wet-sanding and buffing, and that's it.  This "standard" job will probably
be inferior to the standard enamel job (if it is done right -- a big "if"),
but the hot-rodder's job will be vastly superior, leading to the incredibly
deep shine you often see on those 100-point concours winners.

- The big advantage of enamel, of course, is durability.  Enamel not only
resists chipping (and lacquer definitely chips easily) but also fading.  A
typical lacquer finish will fade in a few months and require rebuffing to
bring up the shine again.  Enamels are also less work, if nothing gets
screwed up.  You just spray and that's it.  No more sanding, no more buffing.

- If you want good looks *and* durability, urethane paints might be for you.
Urethanes are an even more recent development than enamels.  They spray very
much like an enamel, but can be rubbed out just like a lacquer.  So, you
could simply spray and be happy with an enamel-like finish, or put in the
extra effort to get something *very* close to the real lacquer-like gloss.

- Urethane is really *great* stuff, but *amazingly* dangerous.  You won't
see this stuff on your new car (EPA rules won't allow auto makers to use it
in mass production), and it may soon be hard for body shops and hobbyists to
buy it.  If you use this stuff, you should do it in a real spray booth with
a real forced-ventilation system, with every part of your body covered in
airtight coveralls.  (Again, some urethane paint suppliers will sell/give
this stuff to customers.  You know, a live customer is a happy customer  :-)

- Of course, most of us don't have access to a real spray booth.  If you can
find a good body shop that uses urethanes, then great.  Or, if you still
want most of the experience of doing it yourself, consider using a lacquer
base-coat with a urethane clear-coat.  The idea is you do the lacquer job
yourself and to your own satisfaction.  Then, take it to the shop for the
urethane clear-coat.  This gives you almost all of the satisfaction and
gloss of a do-it-yourself lacquer job, plus the durability of urethane. 
(Note, however, that the use of a clear-coat may present problems for very
serious concours.  But in that case, I suppose one wouldn't be so interested
in durability.)  My one experience with this technique has been just great
-- the job looks like a lacquer job, but no fading or chipping in over a
year.


What are my favorites?  Well, at home I use lacquers only.  My wife and I
are thinking about kids, and so I just can't justify using anything as toxic
as enamels or urethanes outside of a real spray booth when I can pay a
professional to do it for me.  For durability, an enamel job can be had good
and cheap.  But for durability *and* a great finish, my experience has been
that a lacquer base followed by a urethane clear is a pretty good way to go.
Of course, this entails finding a willing body shop, and sorting through the
various materials to make sure that everything, especially the urethane
clear and the lacquer base, are compatible.  Your paint supplier and body
shop should be helpful here.

Peter


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