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By Bruce W. Maki, Editor
Start:
As part of our
1957 Willy's Jeep
restoration project we painted some parts while they were
removed from the vehicle, such as the hood and front clip.
Earlier these parts were sent to another shop for
sandblasting.
The painting was done by Bob Mapes,
owner of R-Tech
Auto Body in Traverse City, Michigan.
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Warning:
Spray painting can be dangerous, hazardous
to your health, and cause serious property
damage. The painting shown in this article
was done by a licensed professional in a
paint booth with a fire suppression system.
This article should not be viewed as
"instructions" or "advice". This article
is for entertainment purposes only. Any
person who plans on doing their own spray
painting should read the
additional warnings
at the end of this article. |
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After sandblasting, the
Jeep hood had a satin-silver appearance. |
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Bob wiped down the
surface with an ordinary metal preparation
product, which can be found at an automotive
paint supplier.
I understand that many
metal prep products are based on phosphoric
acid. |
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Cleanliness Is Critical:
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Before painting a car, Bob ALWAYS wipes the
surface with a lint-free towel and wax and
grease remover, which is sold in auto body
supply shops. This is very important!
Any oily substance can prevent proper
paint adhesion, or bleed through the paint and
be visible after all the work is done. |
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Applying Primer To Bare Metal:
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Bob mixed some Matrix MP480 Epoxy Primer and began painting the
hood. First he primed around the edges, then he
sprayed from side-to-side while working towards
the middle of the hood. |
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| Once Bob
reached the middle, he quickly walked around and
resumed painting, working toward the edge. |
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After Bob was done applying the
primer, he let it dry for about 20 minutes. This primer did
not require sanding before the color coat was
applied. Note that some types of automotive primers must be
sanded before the color coat is applied. We strongly
recommend following the paint manufacturers instructions.
Applying The Color Coat:
For the color coat, Bob used
Matrix System's Single Stage Red #73218. (The
single stage paint does not require a
clearcoat, although clearcoat may be applied over it.)
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Bob started painting by spraying around the
edges of the hood. |
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| Then Bob
began making side-to-side sweeping passes with
the spray gun, holding the spray tip about 8 to
12 inches from the surface and keeping the gun
perpendicular to the surface being painted. |
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Note how Bob holds the air hose in
his other hand, rather than just letting the hose flop
around. From my experience, it just seems more natural to
hold the hose with the other hand... it keeps the hose away
from the car, and it feels more balanced.
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On the second pass, Bob overlapped the first
pass by about 50%. This "50% overlap" concept
is crucial to getting good results. |
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| Once Bob had
sprayed the hood half-way, he quickly walked
around and began painting from the other side.
Note the angle of the spray gun. When spraying a
flat surface, the gun needs to be tilted forward
so it's perpendicular to the surface being
painted. |
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When Bob reached the bend in the hood, he
tilted the spray gun so it was closer to
being vertical. This change in angle may seem
obvious, but from my own experience as a novice
painter it's easy to forget to turn the gun
upwards as you progress around a bend in the
contour of the car. |
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While moving the spray gun from
side-to-side, I've found a tendency to let the gun rotate
as my arm moves. Whenever I do any spray finishing, I need to
remind myself to keep the gun straight by flexing my
wrist as I move my arm sideways.
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reached the edge, he tilted the spray gun
completely vertical and finished the last few
swaths. |
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Almost done painting... Applying the entire color coat to
this hood
took less than a minute. After Bob painted
some other parts, he spent a few minutes
cleaning out the spray gun with lacquer thinner. |
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Quick
Summary - Cleaning A Spray Gun:
- Empty the unused paint from the cup.
- Pour a few ounces of solvent (typically lacquer thinner)
into the paint cup, swish around, and spray into
a small container. Repeat.
- Dismantle the spray gun by removing the air
cap and orifice. Wash in a dishpan with solvent
specified by paint manufacturer. Pour solvent
into paint cup and let it drain into dishpan.
- Use an air nozzle to blow the solvent from
the spray gun body and parts. When dry,
re-assemble gun.
- Dispose of used solvent properly.
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After applying the color coat to the
hood and front clip, Bob
let the paint dry in his paint booth for about 20 minutes.
Of course, this is a professional paint booth which has a
built-in furnace so the air can be heated to speed up the
drying process. Bob says he usually heats the booth to about
105 degrees Fahrenheit.
While this red paint did not require
a clear coat, Bob still applied it anyway. Applying clearcoat is tricky because it takes MUCH longer to dry, so
it's easy to have problems with runs, drips and sags. The
key is to apply a thin coat, let it dry for
ten minutes or so, then apply a second and third coat (with
ten minute drying time between coats).
Painting A Repaired
Patch Vs.
Painting Bare Metal:
This article
describes the methods used to repaint a car
when all the old paint is removed down to
bare metal. Note that painting a small patch
on a car body can be different.
When applying primer, a special product
called epoxy fill primer is used to
obtain the proper paint thickness so the
repair will blend in with the surrounding
area. The primer is applied so it overlaps
the original paint about 3 to 4 inches. The
primer is "block-sanded" with 320 grit
sandpaper and a rubber-backed sandpaper
holder. For most
do-it-yourselfers, it's advisable to sand,
mask, and repaint the entire body panel,
because blending new paint into existing
paint is very tricky and requires special
techniques. After
repainting an entire body panel, clearcoat
can be applied to the same panel. |
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Warnings About
Do-It-Yourself Spray Painting:
There are some bad
things that can happen when large amounts of
paint are sprayed without the use of a
proper paint booth:
Explosion and/or Fire: Many
automotive paints are oil-based and use
volatile solvents such as lacquer thinner.
When these paints are sprayed, the solvent
can be explosive. Keep away from open flames
or hot surfaces. For example, I've heard of
an explosion and fire happening when
lacquer-based paint was sprayed in the
presence of halogen lights, which get very
hot. Spray painting requires lots
of ventilation.
Health Risks Of Paint Fumes:
Petroleum solvents can make you feel
light-headed, but the bigger problem is that
solvents dissolve the fatty myelin
around your nerve cells. Myelin acts as
electrical insulation for your nerves and
brain, and when this stuff dissolves your
brain can short-circuit. You wouldn't
melt the insulation on the wiring in
your car, would you? Don't do it to your
brain!
If you paint
indoors, wear an organic vapor
respirator. I bought one for about 40
bucks at Home Depot. These things use
activated charcoal filters to absorb all the
volatile organic compounds that pass through
them. Eventually they get plugged up and the
filters need to be replaced. I store my
respirator in a sealed Ziploc bag when not
in use. Overspray:
Even with an HVLP (High Volume Low Pressure)
spray gun, there is still plenty of
overspray. If spraying indoors, the
overspray can cover large portions of your
garage. If spraying outdoors, the
overspray can fall on cars parked nearby. If
you cover your neighbor's house or car with
paint overspray, you may be held liable for
damages. Sometimes overspray wipes off like
dust, but sometimes it sticks really well.
Watch the direction of the breeze, and
observe how far the overspray is travelling. |
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More Info:
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Tools Used:
- HVLP Spray Gun
- Organic Vapor
Respirator
- Air Compressor
- Sawhorse
- Lint-Free Towels
- Ventilation
System
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Materials Used:
- Metal Prep
- Wax and Grease
Remover
- Automotive Primer:
Matrix MP480 Epoxy Primer
- Automotive Paint:
Matrix Single Stage Red #73218
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Related Articles:
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Web Links:
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