197 Chapter 9 Nonstructural Panel Repair
Copyright Goodheart-Willcox Co., Inc.
begins as soon as hardener and filler are mixed. The
mixed filler will stiffen as it cures and will only be
spreadable for a few minutes. Therefore, it is impor-
tant to apply the filler as soon as it is mixed. Once the
mixed filler has cured too much, it is not workable.
C C C C C C C A A A A A A A U U U U U U U T T T T T T T I I I I I I I O O O O O O O N N N N N N N
N Ne Ne ver ve r ret re tu tu rn rn mi m ix ix d ed ed fill f f il il le le r r t to to th t t he he can. c an .
The Th ixed mi d filler fi ll will il l contami in ate he th
unmixed filler.
Use a clean spreader to apply a thin coat of
mixed filler to the low area. Press down hard on the
filler as the first coat is applied. This will squeeze out
the air from under the filler and reduce the number
of pinholes. Pinholes are pockets or voids in cured
filler. Apply additional coats of filler, building up the
filler until an overfill (filler higher than the surrounding
metal) is achieved. After overfilling the low area, use
light strokes with the spreader on the filler to obtain a
smooth surface. Stop working the filler when it begins
to stiffen. Allow the filler to cure. Shop temperatures
below 60°F increase cure time. Clean the mixing
equipment while the filler is curing.
Filling a body line can be difficult. A simple body
line can be filled by spreading an overfill on the peak
of the body line. A complex body line can be repaired
by forming the filler to match the contour of the undam-
aged body line. A body line sander or conformable
sander can be used to mold the filler. Put 2″ (50 mm) ″
masking tape over the contour sander that best
matches the shape of the original body line. Apply the
mixed body filler to the damaged body line and press
the body filler into the proper shape with the contour
sander. Hold or tape the contour sander in place
until the filler hardens. When the filler has hardened,
remove the sander. The filler should be shaped so it
requires little sanding.
Most problems are caused by the filler or hard-
ener itself, the mixing procedure, or the condition of
the application site. To avoid problems, follow these
guidelines:
■ Check the manufacturer’s date on the filler can.
If the filler is over one year old, do not use it. This
rule applies even if the can is unopened.
■ If runny liquid hardener comes out of the tube after
kneading, do not use the hardener.
■ If the metal is below 70°F, warm the metal with a
heat lamp before applying the filler.
■ If the metal is damp, use a heat lamp to warm and
dry the metal before applying the filler.
■ Follow the recommended mixing procedures. Too
much hardener, which is evidenced by a deeply
colored mixed filler, will cause pinholes and a
lack of adhesion. Too little hardener will cause an
insufficient cure (soft filler) and a lack of adhesion.
■ If the filler is to be applied over bare metal, use a
grinder or 80-grit sandpaper to remove the paint.
This procedure will abrade the surface, allowing
the filler to bind to the rough surface.
■ Some manufacturers recommend that filler be
applied over epoxy primer. The bare metal is
sprayed with epoxy primer. Once the epoxy primer
cures, it is scuffed and the filler is applied. Check
the paint manufacturer’s recommended cure time.
It may be as long as 24 hours.
Goodheart-Willcox Publisher
Figure 9-53. Kneading the hardener tube will mix the
hardener.
Goodheart-Willcox Publisher
Figure 9-54. Body filler and hardener are combined
on a mixing board.
Filler
Hardener