Model Car Polishing Technique
February 2002
By Jamie Makin
Step
1 - Preparation:
Recommended
Materials:
Sprue
Cutters
X-acto
Knife
Meal
File(s)
Sandpaper
(400, 600, 800 & 1200 grit)
Putty
Soft
Scrub
Soap
& Water
Plastikote
T235 Grey Primer
Optional
- Plastikote White Primer
Proper
preparation of a model car body is essential for a good finish, but is often an
overlooked step. It is especially critical if you are painting with an airbrush.
A thick coat of paint from a can can hide some flaws, but the airbrush will
highlight them.
Start
by removing all mold parting lines, flash and other imperfections. These are
byproducts of the injection molding process, but do not exist on real cars.
Sprue cutters and a metal file can be useful for thick sprue attachments at
edges. Use the sandpaper and sanding sticks to remove mold lines and for work on
surfaces which need to remain smooth. Fill all seams, scratches, gouges and sink
marks with putty, and sand the putty smooth after it is fully cured. File down
any thickened plastic that may build up along the edges of hoods, trunks,
etc.
For
good paint adhesion, the body must be primed. Plastikote T235 automotive primer
sprays on nicely straight from the can. Two coats are adequate. The primer won't
harm the plastic even though it is lacquer based. However, if you spray lacquer
paint on unprimed plastic, it will craze the plastic, ruining the model.
Although the primer will dry to the touch in a matter or minutes, it is
advisable to let it dry for at least two days, before painting the model. This
allows all the gasses in the lacquer to fully dissipate, preventing problems
with paint sprayed over it. If the primer dries with a slight texture, gently
sand it smooth with 1200 grit sandpaper. Primer will often make previously
overlooked flaws on the model visible. If you see sink marks, scratches, or the
remains of mold lines through the primer, repair them, and then reprime the
surface.
The
grey primer is sufficient for most paints. However, for white, yellow and light
metallic colors, it is recommended to spray two additional coats of white primer
over the gray primer.
Step
2 - Painting:
Good
Paint Choices for Model Cars:
Testors
Model Master (Enamel)
Testors
Acryl (Acrylic)
Plastikote
Spray Cans (Lacquer)
Plastikote
Touch-up Bottle (Enamel)
MCW
(Lacquer)
Tamiya
Spray (Lacquer)
There
are two ways to apply paint to a model car: with a spray can or an airbrush.
Both can yield excellent finished results if done
properly.
Spray
cans tend to build up paint thickness quickly so fewer coats are needed. For
non-metallic colors, 3 colors of paint should be sufficient. The first coat
should be misted on lightly, followed by heavier coats for the second
two.
For
metallic colors, two coats of paint can be sufficient, as long as the color
achieves a uniform consistency in these coats. If not, three coats can be
applied.
Metallic
colors must be covered with a compatible clear coat. Three coats of clear are
recommended for proper polishing. It is Okay to spray acrylic clear over lacquer
or enamels, and it's okay to put an enamel clear over lacquer. But, NEVER spray
a lacquer over an enamel or acrylic. This is a sure way to craze the paint. If
you are in doubt about paint compatibility, test it on a sample piece before
trying it on your model.
An
airbrush will apply paint thinner and more smoothly than is possible wit ha can.
Start by applying 3 - 5 "mist" coats of the color. Spray at 15 - 20 psi, and
allow 10 minutes between coats for lacquers, and 20 minutes for enamels and
acrylics. A mist coat should be thin, cover all areas uniformly, but not look
"wet" when applied.
The
dried look of these coats will actually be flat or semi-gloss. After the mist
coats have built up a solid base of color, apply 4 or more "wet" coats of paint,
allowing 15 minutes between coats for lacquers, and 30 minutes for enamels and
acrylics. Metallic paints should have 4 or 5 wet coats, while non-metallics
should have 5 to 8. A metallic color must be covered with a compatible clear
coat, as described above under the spray can
technique.
Spray
4 - 6 wet coats of the clear coat. Sufficient depth of clear coat must be built
up to avoid polishing through to the metallic layer
later.
After
all layers of paint are applied, it is very critical to allow an adequate drying
time before polishing. Failure to do so can result in polishing down to sticky
layers of paint that are not fully dried. Recommended drying times are as
follows:
Enamels:
3 weeks
Acrylics:
2 - 3 weeks
Lacquers:
7 - 10 days
Because
of the long drying times, it is recommended that the painting of the body be the
first thing you do on a new model project. Then, you can work on the rest of the
model while the body dries.
Step
3 - Polishing
Recommended
Materials:
Detail
Master Polishing Kit, (which includes polishing cloths, rubber sanding block,
polish & directions)
Novus
1 & 2
Flannel
Cloth
Index
Card
White
Cotton Gloves
Your
model will be subjected to a lot of handling during the polishing process, so it
is highly recommended that you wear clean, white cotton gloves while handling
the car.
The
most important step in polishing is doing a thorough job with the first
polishing cloth. Your selection of what cloth to use first should be based on
the finished texture of your paint job. If it came out very smooth with no
embedded dust, starting with the 3600 cloth should work well. A moderate orange
peel with small specks of dust should be started with the 3200 cloth. For very
roughly textured finished or drips and runs, start with the 2400
cloth.
Most
of your polishing time will be spent with this first cloth. Wrap it around the
sanding block, and move it gently back and forth across the surface of the
model. Maintain a uniform back and forth direction. Do not continually change
direction or polish in a circular fashion. Apply only very light pressure to the
block, letting the grit on the cloth do the work.
Be
very careful around sharp edges and contours to ensure that you don't rub
through the paint or clear coat. Polish the model with this cloth until the
entire surface has a uniform flat, dull surface. Although you may be gripped
with fear that you have destroyed the gloss finish, it is essential to actually
make the finish as flat as possible in this first step. This first cloth
essentially removed all damage and imperfections in the paint, while the
remaining cloths will gradually restore the finish to a glossy
shine.
Once
you finish with the first cloth, switch to the next cloth. It is very important
never to skip cloths during this process. Polish the entire surface with this
cloth using very light pressure, but moving back and forth perpendicular to the
direction you used for the first cloth. Continue with this cloth until the
surface is uniformly smooth. The second cloth shouldn't take nearly as long as
the first, but take care to be thorough with it. Check your work under a bright
halogen desk lamp. After you are done with each cloth, move to the next cloth,
again reversing the direction each time.
Each cloth will make the finish glossier, and by the time you are done
with the 6000 grit cloth, you should be able to see reflections in the paint
when you hold it under the lamp. Continue working your way up to the 12000-grit
cloth.
After
finishing with the polishing cloths, the model will have a smooth, glossy shine,
but that shine will be a bit hazy. This haze is polished out with a series of
liquid polishes. Use only a flannel cloth for these liquid polishes. Anything
else can cause scratches to your finish. Dampen a small area of the flannel
cloth, and use it to apply small amounts of the polish that came with the
polishing kit. Apply this like care wax, using circular motion and more pressure
than you used with the polishing cloths.
When
the polish dries on the surface, wipe it away with a clean, dry portion of the
cloth. Next, do the same thing with the Novus 2. This should restore the finish
to a glossy, haze-free shine. If there is still some haze or fine scratches,
repeat the application of the polish and the Novus 2 until you are
satisfied.
During
the process of applying liquid polish, it is inevitable that a good amount of
polish will work its way into panel lines and crevices. Do not use a sharp tool
like an X-acto blade or toothpick to scrape this polish out. Instead, let the
polish dry thoroughly. Then, cut an index card into tiny strips. Use the corners
and edges of this card to scrape the polish away. This is the safest way to do
it without chipping or scratching the paint.
Finally,
clean the entire model with Novus 1. This provides a protective, static-free
layer of shine to your finished paint job. Just be aware that you cannot paint
over Novus 1 - (the paint tends to "bead up.") It is recommended that you do any
trim painting or detailing before the Novus 1. You can, however, apply details
after using Novus 1.
Some
Final Thoughts:
Preparing,
painting and polishing a model care finish is a time consuming task that will
take a lot of patience. However, it is not difficult, and the results of your
hard work will be very satisfying. Remember, that what I have presented here is
the technique and materials that I have found worked well for me over the course
of building a dozen models. There are other methods and materials that may work
just as well, if not better for you. Don’t be afraid to experiment and try new
things when working on your own models.
Best
of luck to you in your next modeling
project.
visitors.
Copyright © 2007 by Anthony
I. Wootson & Jamie Makin. No material may be reproduced without permission of
Anthony I. Wootson. Unauthorized duplication is
prohibited.