Discover
Auto Paint Repair...
The Problem Conditions,
Causes,
Preventions and
Solutions.
If auto
painting is a new venture for you, it is imperative that you
understand the basics of do it yourself auto body paint
repair.
On this
page you will find a treatment of the most common paint finish
problems. This format details the
condition of the
problem,
it's causes, prevention and the best
solution.
We always
heartily recommend anybody to spend an adequate amount of time
preparing their vehicle’s surface for paint and therefore
minimize the need for car paint repair
afterwards.
Too many
times, enthusiastic rookie painters get ahead of themselves.
They believe that a thick coat of paint will hide blemishes or
flaws, it simply won’t. Don’t rush into
things.
If you plan
on spending a day or two just to prepare your car’s body
surface for paint, the need for auto paint repair won't be
necessary.
Here our
list of common paint problems:
|
Bleeding
Condition
: Original
finish discoloring or color seeping
through the new topcoat
color.
Causes
 |
Contamination
- usually
in the form of soluble dyes or
pigments on the older finish before
it was repainted. (This is
especially true with older shades
of red). |
Prevention
 |
Thoroughly clean areas to be
painted before sanding, especially
when applying lighter colors over
darker colors. |
Solution
: Apply two
medium coats of Bleeder seal in
accordance with label instructions. Then
reapply color coat.
|
|
|
Blistering
Condition
: Bubbles
or pimples appearing in the topcoat film,
often months after
application.
Causes
 |
Improper surface
cleaning or
preparation |
Tiny specks of dirt left on
the surface can act as a sponge and hold
moisture. When the finish is exposed to the sun
(or abrupt changes in atmospheric pressure),
moisture expands and builds up pressure. If the
pressure is great enough, blisters
form.
 |
Wrong thinner or
reducer |
Use of a fast-dry thinner or
reducer, especially when the material is
sprayed too dry or at an excessive pressure.
Air or moisture can be trapped in the
film.
 |
Excessive film
thickness |
Insufficient drying time
between coats or too heavy application of the
undercoats may trap solvents which escape later
and blister the color coat.
 |
Contamination of
compressed air
lines |
Oil, water or dirt in
lines.
Prevention
 |
Thoroughly clean areas to be
painted before sanding. Be sure
surface is completely dry before
applying either undercoats or
topcoats. Don't touch a cleaned
area as the oils in your hands will
contaminate the
surface. |
 |
Select the thinner or reducer most
suitable for the existing painting
environment
conditions. |
 |
Allow proper drying time for
undercoats and topcoats. Be sure to
let each coat flash before applying
the next. |
 |
Drain and clean air pressure
regulator daily to remove trapped
moisture and dirt. Air compressor
tank should also be drained
daily. |
Solution
: If damage
is extensive and severe, paint must be
removed down to undercoat or metal,
depending on the depth of blisters. Then
refinish. In less severe cases, blisters
may be sanded out, resurfaced and
re-topcoated.
|
|
|
Blushing
Condition
: A milky
white haze that appears on lacquer
films.
Causes
 |
In hot humid weather, moisture
droplets become trapped in the wet
paint film. Air currents from the
spray gun and the evaporation of
the thinner tend to make the
surface being sprayed lower in
temperature than the surrounding
atmosphere. This causes moisture in
the air to condense on the wet
paint film. |
 |
Excessive air
pressure. |
 |
Too fast a
thinner. |
Prevention
 |
In hot humid weather try to
schedule painting early in the
morning when temperature and
humidity conditions are more
suitable, use acrylic lacquer
thinner. |
 |
Use proper gun adjustments and
techniques. |
 |
Select the thinner that is suitable
for existing painting environment
conditions. |
Solution
: Add
retarder to the thinned color and apply
additional coats.
|
|
|
Chalking
Condition
: Formation
on the finish caused by pigment powder no
longer held by the binder, which makes
the finish look dull.
Causes
(other than
normal exposure)
 |
Wrong thinner or reducer, which can
harm topcoat
durability. |
 |
Materials not uniformly
mixed. |
 |
Starved paint
film. |
 |
Excessive mist coats when finishing
a metallic color
application. |
Prevention
 |
Select the thinner or reducer that
is best suited for existing
environmental
conditions. |
 |
Stir all pigmented undercoats and
topcoats
thoroughly. |
 |
Meet or slightly exceed minimum
film
thicknesses. |
 |
Apply metallic color as evenly as
possible so that misting is not
required. When mist coats are
necessary to even out flake, avoid
using straight
reducer. |
Solution
: Remove
surface in affected area by sanding. Then
clean and refinish.
|
|
|
Chemical
Staining
Condition
: Spotty
discoloration of the
surface.
Causes
 |
Atmospheric contamination falling
on the finish in the presence of
moisture or rain - usually due to
adjacent industrial
activity. |
Prevention
 |
Avoid contaminated atmosphere or
wash surface with detergent and
water as soon as possible after
exposure. |
 |
Apply clear
coat. |
Solution
: After
washing with detergent and water, rub
affected area with rubbing compound and
polish. In severe cases, sand to prime
and refinish.
|
|
|
Chipping
Condition
: Small
chips of a finish losing adhesion to the
underlying layer (substrate) usually
caused by impact of stones or hard
objects.
|
|
|
Cracking (Line Checking,
Micro-Checking)
Condition
: A series
of deep cracks resembling mud cracks in a
dry pond and in no definite pattern, they
are usually through the color coat and
sometimes the undercoat as
well.
Causes
 |
Excessive film thickness.
(Excessively thick topcoats magnify
normal stresses and strains which
can result in cracking even under
normal
conditions.) |
 |
Materials not uniformly
mixed. |
 |
Insufficient flash
time. |
 |
Incorrect use of
additive. |
Prevention
 |
Don't pile on topcoats. Allow
sufficient flash and dry time
between coats. Do not dry by gun
fanning. |
 |
Stir all pigmented undercoats and
topcoats thoroughly. Strain and
where necessary, add Fish Eye
Eliminator to
topcoats. |
 |
Read and carefully follow label
instructions. (Additives not
specifically designed for a color
coat may weaken the final paint
film and make it more sensitive to
cracking.) |
Solution
: The
affected areas must be sanded to a smooth
finish or in extreme cases removed down
to the bare metal and
refinished.
|
|
|
Crazing
Condition
: Fine
splits or small cracks often called
'crowsfeet' that completely checker an
area in an irregular
manner.
Causes
 |
Work area too cold. (Surface
tension of original material is
under stress and literally shatters
under the softening action of the
solvents being
applied.) |
Prevention
 |
Select the thinner or reducer that
is suitable for existing work area
conditions. Schedule painting to
avoid temperature and humidity
extremes in the work area or
between temperature of work area
and your paint job. (Bring the
vehicle to room temperature before
refinishing.) |
Solution
: There are
two ways to overcome
crazing:
 |
Continue to apply wet coats of
topcoat to melt the crazing and
flow pattern together (using the
wettest possible solvent work area
conditions will
allow) |
 |
Use a fast-flashing thinner which
will allow a bridging of subsequent
topcoats over the crazing
area. |
|
|
|
Die Back
Condition
: Loss of
gloss after
application.
Cause
: Improper
evaporation of solvent or poor initial
cure.
Suggested
Corrective Action
Checklist
 |
Check if the imperfection is on the
whole unit or in a specific
area. |
 |
Check other units to determine if a
pattern is beginning to take
place. |
 |
Check for too fast a solvent
selection. |
 |
Check for cool temperature during
cure. |
 |
Check for lack of airflow during
cure. |
 |
Check for improper film build
up. |
 |
Check for improper flash
times. |
 |
Check for incompatible
products. |
|
|
|
Dirt
Condition
: Small
bumps deposited in, on, or under the
paint film.
Cause
: Foreign
particles entering the wet paint
film.
Suggested
Corrective Action
Checklist
 |
Check if the imperfection is on the
whole unit or in a specific
area. |
 |
Check other units to determine if a
pattern is beginning to take
place. |
 |
Check paint mixing/filtration
process (was a strainer in place
atop the paint cup when pouring in
paint) |
 |
Check the spraying environment
(booth, garage,
workshop) |
 |
Check preparation process of unit,
tacking, solvent wash,
etc. |
 |
Check painter's
clothing. |
 |
Check the spraying equipment (was
it thoroughly cleaned after
previous use) |
 |
Check used paint filters for
contamination. |
 |
Check for use of anti-static wipe
or spray
products. |
|
|
|
Dry Spray
Condition
: A rough,
textured surface often confined to a
small area.
Cause
: Paint
that lacks the ability to flow
properly.
Suggested
Corrective Action
Checklist
 |
Check if the imperfection is on the
whole unit or in a specific
area. |
 |
Check other units to determine if a
pattern is beginning to take
place. |
 |
Check if the defect is specific to
one color or many
colors. |
 |
Check for a proper film build
up. |
 |
Check for excessive film build
up. |
 |
Check the distance of the spray gun
from the surface when spraying.
(You should always hold a paint gun
at right angles to the surface
being painted from a distance of
6-10 inches.) |
 |
Check reducing solvent selection
and spray
viscosity. |
|
|
|
Featheredge
Splitting
Condition
: Appears
as stretch marks (or cracking) along the
featheredge. Occurs during or shortly
after the topcoat is applied over lacquer
primer.
Causes
 |
'Piling on' the undercoat in heavy
and wet coats. (Solvent is trapped
in undercoat layers which have not
had sufficient time to set
up.) |
 |
Material not uniformly mixed. (Due
to the high pigment content of
primer, it's possible for settling
to occur after it has been thinned.
Delayed use of this material
without restirring results in
applying a film with loosely held
pigment containing voids and
crevices throughout, causing the
film to act like a
sponge.) |
 |
Wrong thinner. |
 |
Improper surface cleaning or
preparation. (When not properly
cleaned, primer coats may crawl or
draw away from the edge because of
poor wetting and
adhesion.) |
 |
Improper drying. (Fanning with a
spray gun after the primer is
applied will result in drying the
surface before solvent or air from
the lower layers is
released.) |
 |
Excessive use (and film build) of
putty. |
Prevention
 |
Apply properly reduced primer in
thin to medium coats (150%
reduction) with enough time between
coats to allow solvents and air to
escape. |
 |
Stir all pigmented undercoats and
top coats thoroughly. Select
thinner that is suitable for
existing work area
conditions. |
 |
Select only thinners that are
recommended for existing work area
conditions. |
 |
Thoroughly clean areas to be
painted before
sanding. |
 |
Apply primer in thin to medium
coats with enough time between
coats to allow solvents and air to
escape. |
 |
Lacquer putty should be limited to
filling minor imperfections. Putty
applied too heavily (or too thick)
will eventually shrink causing
featheredge
splitting. |
Solution
: Remove
finish from the affected areas and
refinish.
|
|
|
Fish Eyes
Condition
: Tiny
surface finish blemishes that resemble
small circles of popped paint bubbles,
which seem to occur almost as soon as
paint hits an auto body
surface.
Causes
 |
Improper Surface
Cleaning Or
Preparation |
Many waxes and polishes
contain silicone, the most common cause of fish
eyes. Small traces of silicone do not allow
paint to settle evenly; rather they cause
material to encircle the speck of silicone and
form a fish's eye.
Silicone adheres firmly to
the paint film and requires extra effort for
its removal. Even small quantities in sanding
dust, rags or from cars being polished nearby
can cause this failure.
-
Check
for possible contamination in paint
materials.
-
Check
for painter contamination, skin oils,
perspiration, greasy foods,
etc.
- Check for any
oils or contamination that might get into the
spray area.
- Check for
proper cleaning procedures prior to
refinishing.
- Check airborne
contamination in spray area.
 |
Effects of the
old finish or previous
repair
:
Old finish or previous repair
may contain excessive amounts
of silicone from additives
used during their
application. Usually solvent
wiping will not remove
embedded
silicone. |
 |
Contamination of
air lines
:
Check for oil in air lines and
spray equipment. |
Prevention
 |
Precautions should be taken to
remove all traces of silicone by
thoroughly cleaning with wax and
grease remover. (The use of Fish
Eye Eliminator is in no way a
replacement for good surface
preparation). |
 |
Add Fish Eye
Eliminator. |
 |
Drain and clean air pressure
regulator daily to remove trapped
moisture and dirt. Air compressor
tank should also be drained
daily. |
Solution
: After
affected coat has set up, apply another
double coat of color containing the
recommended amount of Fish Eye
Eliminator. In severe cases, affected
areas should be sanded down and
refinished.
|
|
|
Gloss/DOI
Description
: DOI is
the sharpness by which images are
reflected in the surface of a top coat
finish. The images are usually evaluated
for 90-degree angle. Gloss measures the
amount of light reflected from a paint
surface read at 20- and 60-degree
angles.
Cause
: Poor DOI
is caused by an non-smooth or irregular
top coat surface and/or low gloss. Low
gloss is caused by an improper topcoat
application process or improper solvent
selection.
Suggested
Corrective Action
Checklist
| |