Body &
PaintBody &
PaintPaint Technologies
Bottom line on paint=money. The farther you strip the car (of parts and old
finish), the better the results of a paint job. While good results can be
obtained "taping out" certain areas, these areas will be more prone
to chipping, lifting etc. As to clear coats. Porsche did/does not typically
clear coat solid non-metallic colors such as guards red. That being said, you
will get better results (in the long run) using a base coat/clear coat system,
provided it is of high quality. DuPont Chroma series, PPG Delstar, Glasruit,
Sikkens, etc. The latest clear coats are loaded with UV protection, and will
give you a much richer, deeper finish. A common "trick" of custom
painters when clear coating solid colors (like red, black, etc) is to mix a bit
of the color in with the initial clear coats for a really deep, wet look. Below
are some basic guidelines and info. Hope you find it helpful.
One-part enamels: Don't waste you time or money.
Two-part enamels: (ie. DuPont Imron, a catalyzed polyurethane enamel)
Advantages - Good gloss, very hard, durable.
Disadvantages - (some say too brittle), can be tricky to touch-up orrepair,
expensive.
Base coat/clear coat: (Two basic types)
"Traditional" Lacquer:
Advantages - Easiest to shoot, beautiful, deep finish, great for rarely driven
show cars.
Disadvantages - Fragile, prone to damage from hard water, chemicals, bird
droppings. Not recommended for daily drivers.
Catalyzed urethane: (Most common)
Advantages - Best UV protection for paint, "show car" deep, wet
gloss, very chemical resistant, easy to touch-up. Results equal to or better
than lacquer in depth and gloss. Shallow defects can be "finessed"
out without disturbing the base color below.
Disadvantages - Mostly cost. About $250.00 a gallon for high quality.
One thing to bear in mind. The single most important factor in determining the
final quality of a paint job is preparation. That is; proper stripping,
sanding, filling, priming. That is why (as a _general_ rule) it is best to
remove as many parts, and as much of the old finish as your budget will allow.
Best always,
Dave
Alright here goes. First you have to remember what we were going for. Since
we were rebuilding late model wrecks we were attempting to get a good looking
factory job - not produce a show car with 40 coats of hand rubbed lacquer. This
was back in the 1970's and the choices were basically enamel and Acrylic
Lacquer. Most cars were painted in some form of enamel or for many GM cars
Acrylic Lacquer.
One of the problems with combining enamel with Acrylic is that it is easy to
get reactions. One of the ways around this is to primer the entire car. This is
a pain if you are not going to strip the car of all of the chrome and lights -
which we generally did, but there always are a few gaskets and accessories that
are difficult and time consuming to strip. Adding an extra coat of primer
complicates things, can show though on a scratch, takes more time and does not
necessarily give the best job.
One of the ways around this is to spray, after the body work is complete, is a
base coat of color with a very fast thinner. This has the advantage of keeping
the number of coats down. Since lacquer dries very quickly there is no waiting.
The first coat is inspected for imperfections and all of the minor nicks and
sand marks filled. We use to use lacquer primer straight from the can with no
thinning and put it on with thin aluminum applicators. This left very little
sanding. Since first coat was put on almost dry will be dull and a bit rough.
This is wet sanded with 600, blending the primer patches in with the paint.
Where lacquer goes on thinner than other paints it requires better preparation
with the bodywork. The first coat process helps cut the time on getting the
bodywork perfect before paint. Remember we were doing production work so the
quicker the car got done the better as long as quality was not compromised. The
first coat acts as a sealer so there is a good base to build from.
The second coat is put on with a slower thinner and rather thick. Again this
dries fast and does not leave a gloss. Sometimes the second coat is enough but
if after drying for 24 hours to let all of the thinner evaporate, minor
imperfections come up, they are once again filled and the car hand sanded again
with 600. To get a good job the second coat should be put on by someone that
knows haw to handle a spray gun as the smoother it goes on the better the final
job.
If there are some imperfections then they again are filled with primer and
anded out. The final coat is put on with an even slower thinner and some gloss
is obtained. This is nice for door jambs and other hard to rub out areas.
Once the final coat has set 24 hours it is rubbed out - we use to do this by
hand - but labor was cheap and a buffer would probably work just as well.
No wax was applied to the job only hand rubbing. Any over spray on the gaskets
was cleaned by scraping with the same aluminum applicators. Since lacquer is
brittle when first applied it is very easy to get exacting detail. I have had
many people - including body men and dealers - look at the finished job and not
believe the car was a re-paint. In fact we sold a number of the cars we did
directly to dealers that were short the models we were working with.
After sitting for a couple of weeks - preferably in the sun - the car was hand
rubbed again with a fine compound and waxed. Done correctly this is a job that
should last as long as any other paint job, hold up better and continue to
improve with each clean up and wax job. Unlike enamel it will not develop swirl
marks from buffing, have bits of dirt in it (there is no need for a high end
booth since the lacquer dries so quick), chip as easily.
After 150K on my other Porsche there were no rock chips in the hood or fenders
and as I said a taxi driver walked on the hood.. The rate of oxidation is much
less and a panel can be repaired without having to repaint the entire panel. In
the old days body shops used to use Acrylic Lacquer to do touch ups and minor
dings. The problem with that method that while it was quick and looked good
when the job was done the enamel fades quicker that the lacquer patch and the
patch will standout after a while. But patching lacquer on lacquer there is no
problem..
I have tried a number of systems that use catalysts over the years and the
latest system is by far the best that has been developed. But they all have one
problem in common - the hardness. It is very difficult to "color"
sand these and buffer out any problems that show up in the job. The depth is
obtained by clear coating, which can chip as well. With lacquer the depth is
obtained naturally - of course you can clear coat lacquer too, but I never
found it necessary. One possibility is to mix part color and part clear in the
final coat for depth.
Dan
Question
For putting something under the wax (i.e., paint) what do you think?
Acrylic enamel or acrylic lacquer? I need a re-spray. I've had cars with hand
rubbed Ditzler acrylic lacquer and the finish was gorgeous, but rock chips
abound!
Dan Perez
Answer
Dan,
Depending on how and when you drive your 928 you have a few things to consider.
With a low nose exposing a large part of the front of the car to
"aero" streaming, stone chips are a reality. A bra will of course
help you here if you are diligent.
Acrylic lacquers are probably the oldest paint used on cars today. Acrylic
lacquers will provide excellent finishes, but are subject to chipping and wear.
They also need to be routinely sealed with a good wax. The finish can be
fantastic because of all the hand finishing that is possible. Spray gun errors
can be corrected and a mirror finish is possible. You can apply lacquer with a
mop and achieve a great finish! BTDT Acrylic enamels are also available in the
same colors. Enamels are not as forgiving in spray technique, unless a clear
coat is used, but are easier to maintain. Clear coats also have sun blockers
that can extend finish life if you care is out in the sun a great deal. Enamels
and clear coats still need waxing for full protection.
To add still further confusion, urethane paints are available. urethanes
(modified enamels) are some of the highest performance paints in use. These are
usually two-component products and are used on everything from trucks the
commercial airplanes. They are long lasting, chemical (fuel, antifreeze &
brake fluid) resistant and very chip resistant (and key resistant). Most colors
are available as well. The trick with urethanes is having a quality shop do the
spray in order to get a good automotive finish. How many commercial airliner
concourses have you ever seen? We won't even get into powder coatings at this
time.
I would suggest taking some time and visiting a few good shops. Talk with them
about what they would recommend and why. Consider how you use your car, does it
sit outside a lot?, Can it be easily vandalized (key scratches), is it a real
garage queen in almost concours condition at all times? Get opinions and prices
and then decide.
Also talk with them about stripping the old finish to bare metal/plastic. Then
using a special primer(s) for all the various substrates to be refinished. Many
good shops will also dismantle hoods, fenders and bumper covers during a
quality respray. Check them out.
Good luck.
Ed B