Kevin,
I decided to post this since it may be of interest to the
general list. If you pay someone to wash your car you can ignore
this.
Kevin Meek wrote:
> I just painted our Alpine in using PPG Concept single stage
> urethane. Although I painted it in the garage, I still got
> a fair amount of dirt in the finish. I've painted several
> cars, but have never been brave enough to color sand once
> the final coat goes on. Do you have any advice or perhaps
> you could point me towards a reference on how to color sand
> and polish this finish properly...thanks!
> ............................................................
> Kevin Meek (kevnmeek@netcom.com) Sunbeam Tiger Mk 1A
> Santa Cruz, California Sunbeam Alpine S3 GT
Talk to your supplier of the paint about dry time. If you didn't
add a hardener you may have to wait 6-8 weeks before polishing.
If it is metallic, sanding through layers can often cause
visible blemish's. It would be helpful to visit your local book
store and thumb through some "How To" books on refinishing, or
go to amazon.com, they have several. I have a good one at home
that I will try to find, and give you the name.
In general here are some of the "tricks" that I have learned
(Sometimes the hard way!). This one reason why good paint jobs
are expensive.
1. Never use your bare hand on the sand paper.
2. The body supply shop should have neoprene sanding pads that
can be used on curved surfaces, like the tops of fenders. The
sides, doors, hood, and trunk should be sanded with with a
harder rubber block. These are usually flat on one side and
curved on the othr and about 2.5x4 inches.
3. Use 1200 or 1500 sandpaper. 1500 is safer, because it cuts
slower and requires less polishing.
4. Use lots of clean water. If you use a bucket, change it
often. A dribbling hose works well to keep the surface wet.
Clean the sandpaper regularly by rinsing in clean water and
lightly rubbing it with you hand.
5. When sanding the pressure will vary. You can use moderate
pressure with the hard block on flat surface, but as soon as the
surface starts to curve, ease up up on the pressure and CHECK
YOUR WORK OFTEN. Remember, it is pressure between the sandpaper
and the paint that does the work, not force. So, as the area
being sanded is reduced you must reduce the force being applied.
This applies to moderate curves as well, since the crown of the
curve will bear most of the force. Go slow until you get the
hang of it.
6. Checking your work. If you want a mirror like surface with no
orange peel, use a squeegee to check progress. Use a small 1/8
thick hard rubber pad, with a straight edge for a squeegee.
These are used to apply spot putty and are available at the
paint supply store. After sanding a few strokes, use the
squeegee to dry the area, like you would on a window. The sanded
paint will appear dull, and the remaining orange peel
depressions will stand out as shinny spots. Sand a few more
strokes and recheck. You want a smooth uniformly dull surface.
Use judgment, if a flaw is too deep, don't try to remove it
completely, you may sand through the surrounding paint. Stop as
soon as a uniform surface is achieved. Don't try for perfection.
You would rather have a little peel in a few spots than no
paint.
7. Sand parallel to edges and creases, NEVER ACROSS ONE. I wrap
a finger around the block and use the edge or crease to guide my
finger in order to maintain the sanding block about an 1/8 inch
distance from the edge. If it is important to you finish the
last 1/8", do it very carefully by itself. Work closer to the
edge but never on it. USE VERY LIGHT PRESSURE. CHECK YOU WORK
OFTEN.
Polishing
1. The large flat surfaces can be machine polished. Meguiar's
products are good, available and come with a pamphlet that
describes the process.
2. Two steps is usually sufficient for a non-show car. The first
step is a polish and the second is a swirl removal, or fine
polish.
3. Tape the edges of the panel you are going to polish with 1/4"
masking tape. Wrap the tape around the edge. Don't forget the
adjacent edges, ie: if you are polishing a door, tape the door
edges and the adjacent fender edges. This will prevent burning
the paint on the edge with the buffer.
4. Use a low speed (1000 rpm) buffer. Either a foam pad or wool
pad will work. If you use wool you have to keep it from getting
clogged. The body shop supply store has a simple tool that
unclogs the pad.
5. Keep one pad for initial polish and a separate one for final
polish.
6. Keep the pad flat and use light pressure.
7. Apply the compound to the paint and spread with the buffing
wheel. Buff a 2 square foot section at a time. Keep the wheel
moving back and forth over the surface using a light pressure.
Buff until the compound dries and the shin starts to come
through. Then wipe with a clean cheese cloth or soft terry cloth
towel. Repeat if necessary.
8. When approaching and edge, hold the buffer such that the
surface of the pad is moving from the panel toward the edge.
Don't allow it to move from the edge toward the panel. If you
slip up occasionally the tape will save you, because you will
have to burn through the tape before getting to the paint and
you will see the damage on the tape.
9. After finishing the panel repeat with the finer polish.
10. Repeat this until the entire car is done. (You could do all
the initial buffing and then change to the final.)
11. Remove the tape from the edges and polish up to the edge by
hand. This is the only time I don't use a block. You need to
polish using strokes parallel to the edge, using a clean cheese
cloth or soft terry cloth towel. Use you finger tips and press
lightly. Don't go over the edge.
12. Wax using Meguiar's Cleaner wax, and use Meguiar's Detail
cleaner between waxes. If the car is kept in a garage and
cleaned with the detailer you'll never have to use water.
Good luck!
Craig Wright
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Craig Wright Product Design Group, Inc.
craig@p-d-g.com 4635 Viewridge Ave.
(619) 569-3484 x309 San Diego, CA 92123
fax: (619) 569-3490 http://www.p-d-g.com
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