• Tom Hunt

CAR PAINT DEFECTS: WHAT CAUSES THEM?

Got a floaty silver you just can't blend right? Has one of your customers come back with flaking paint? Let's check out what may be causing the problem.


Mottle or "floaty" basecoat

Usually happens with light metallics, especially silvers, creating a spotty or floaty appearance in the paint.


How it potentially happens:

  • Wrong basecoat thinners used for conditions

  • Incorrect mixing of basecoat

  • Spraying the paint too wet or wrong gun pressure

  • Basecoat curing time too short before clearcoat

How to remedy it:

  • Avoid spraying metallics too wet

  • Keep gun angle parallel to the panel being sprayed

  • Use correct thinner for spraying conditions

  • Refer to TDS to the specific paint system


Flaking Clearcoat

When the clear coat has lost adhesion to the basecoat.


How it potentially happens:

  • Flash off time of final basecoat too short

  • The wrong ratio used on the clearcoat

  • Excessive basecoat film thickness

How to remedy it:

  • Fully remove all affected paint and refinish


Bare plastic adhesion loss

When the paint has started flaking away directly from the plastic substrate.


How it potentially happens:

  • Release agent not removed properly from cleaning the plastic

  • Improper preparation technique used

  • Wrong sealer/primer used

  • Plastic adhesion promoter not used

How to remedy it:

  • Remove all paint layers from the plastic, prepare properly and refinish.


Bleeding through paint

Caused by the hardener from the polyester filler seeping through the paint causing a stain/discolouration under the paint.


How it potentially happens:

  • Use of too much hardener in the filler

  • Incorrect mixing of filler

  • The reaction of the old paint and filler

How to remedy it:

  • Remove filler completely, repair and refinish

  • Isolate the old paint with a suitable sealer before applying filler


Paint blisters

Bubbles in the paintwork appearing from underneath.


How it potentially happens:

  • Moisture trapped underneath paint film from incorrect cleaning

  • Humidity too high in spraying conditions

  • Contamination in airlines

  • Too much film thickness trapping water/solvents - not dried properly

How to remedy it:

  • Remove affected paintwork completely and refinish


Edge to edge colour not matching

When the freshly paint panel colour differs from the adjacent panel that has not been painted


How it potentially happens:

  • Spray gun incorrectly set up to the wrong pressure

  • The adjacent panel has naturally changed colour from weathering

  • Too wet (creates darker shade) or too dry (creates lighter shade)

  • Colour not stirred or mixed properly

How to remedy it:

  • Blend the adjacent panel/s

  • Create spray out cards to identify the correct mix and shade


Paint cracking/crazing

When paint over time develops deep cracks within the paint finish.


How it potentially happens:

  • Too much film build

  • Paint materials not mixed correctly

  • Excessive or incorrect use of additives

  • Using incompatible products

How to remedy it:

  • Remove affected paint down to bare metal and refinish.


Edge mapping

When the paint surface appears to have map like edges in isolated areas


How it potentially happens:

  • The trapped solvent in undercoats

  • Primer not mixed thoroughly

  • Finishing repair in too coarse sandpaper grade

  • Using a spray gun to dry paint creating a paint skin instead of drying correctly

How to remedy it:

  • Remove affected paint down to the affected area and isolate or bare metal and refinish


Have you ever noticed some poor previous paintwork on a customers car?


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