By studying paint defects, you can identify possible causes in the workshop or garage and help find solutions to avoid such problems in the future. Painting is an art that’s perfected by practice. But this kind of tough when you’re a hobbyist who may only paint one vehicle a year. With this in mind, we decided to try and put together a bit of a primer (no pun intended) referencing some of the most common paint problems many of us have or will encounter during the course of any paint job or jobs.

Incorrectly prepared substrates and use of paint materials can result in a flawed paint job and let’s face it we all make mistake. So, it’s a good idea to learn some of the causes and cures.  Factors in the paint process/working environment can also affect the end result such as humidity, temperatures, dry times, film thickness ect. Much of this can depend on the painter’s craftmanship and experience. Hopefully the following information will help some of us novice painters identify and with any luck rectify any situations that’d otherwise could have us tearing our hair out or tossing our spray guns in the trash bin.

Fish Eyes or Craters

Identification: Appears as a small crater-like opening in the finish after it has been applied. Appear either during or shortly after you lay down a coat of paint or primer (though primer is often much more forgiving).

Causes:

  • Oil, wax, grease or silicone contamination. Many waxes and polishes contain silicone – the most common cause of fish eye or craters.
  • Contaminated air lines.
  • Effects of old finish and previous repair (May contain excessive amounts of silicone).
  • Polishes, aerosol sprays that contain silicone (Interior cleaners).

Prevention:

  • Thoroughly degrease surface with a wax and silicone remover.
  • Regular maintenance of air supply/equipment.
  • Add fish eye eliminator.

Repair Process:

  • In severe cases, affected areas should be sanded down and refinished.
  • Apply mist coat.
  • Use fish eye remover (in severe cases).

Note: A mold-release agent on a new fiberglass body is another really common culprit.

Chipping

Identification: Small chips of finish losing adhesion to the substrate.

Causes:

  • Improper cleaning or preparation.
  • Improper metal treatment.
  • Materials not properly mixed.
  • Failure to use proper sealer.

Prevention:

  • Degrease and prepare substrate carefully.
  • Use correct metal conditioner. (e.g. Selft Etching Primer).
  • Ensure all materials are measured and mixed uuniformly.
  • Use compatible products/follow maunfacturers instructions.

Repair Process:

  • Remove finish from an area slightly larger than the affected area, sand smooth, prepare metal and refinish.

Blushing (Milkiness)

Identification: A milky white, grey cloud appears on the surface of the paint film immediately or shortly after application.

Causes:

  • When spraying during humid conditions, air from the spray gun and solvent evaporation lowers the substrate temperature below the dew point, causing moisture in the air to condense in or on the paint film. The condition is aggravated when too fast drying or unbalanced thinner/reducer is used.

Prevention:

  • Thoroughly degrease surface with a wax and silicone remover.
  • Regular maintenance of air supply/equipment.

Repair Process:

  • Should blushing occur during application: a) apply heat to the affected area. OR b) add retarder and apply additional coats.

Chalking – Fading, Oxidation, Weathering

Identification: A chalk white appearance on the surface of the paint film.

Cause:

Pigment is no longer protected by resin, resulting in a powder-like surface and lack of gloss due to:

  • Natural weathering of paint film.
  • Improper application of paint material.
  • Excessive generic thinner/reducer and/or hardener in the paint material.

Prevention:

  • Weekly washing and occasional polishing or waxing will remove oxidation from the finish.
  • Thoroughly stir, shake or agitate all paint materials.
  • When spraying single stage metallic finishes, apply mist/fog coats panel by panel while finish is still wet.
  • Use recommended thinner/reducer/hardener and measure accurately.

Repair Process:

  • Compound to remove oxidation and polish to restore gloss.
  • Or sand to remove ‘weathered’ paint film refinish.

Clearcoat Yellowing

Identification: Clearcoat has a yellow hue to it (pretty obvious).

Causes:
New paint:

  • Dirty mixing equipment.
  • Too much accelerator (i.e. kicker) used.

Old paint:

  • Clearcoat is too thin.
  • Contaminated hardener.
  • No cross link.

Repair Process: Affected areas must be sanded smooth, sealed and refinished.

Edge Mapping – Edge Ringing, Featheredge Lifting

Identification: Raised or lifted edges in the wet or dry paint film that outline sand-throughs or featheredges. You’ll recognize it as a wrinkled area outlining a repaired area. 
Cause:

Solvent from the new topcoat penetrates a solvent sensitive substrate causing a lifting or wrinkling that outlines the featheredge.

Prevention:

Check questionable finishes by rubbing a small inconspicuous area with a shop towel saturated with lacquer thinner. Finishes susceptible to lifting will soften, wrinkle or shrivel as lacquer thinner is applied. If any of these reactions occur, the following recommendations should be considered:

  • Use acrylic urethane primer surfacer, waterborne primer surfacer or an acrylic lacquer primer surfacer thinned with non-penetrating thinner over sensitive substrates.
  • Use 400 or finer grit sandpaper when featheredging.
  • Avoid sanding through insoluble topcoat colour or clear, exposing solvent sensitive or soluble finishes.

Repair Process:

  • Sand sooth or remove the affected area. (Final sand with 400 or finer grit sandpaper).
  • Isolate affected area with two component primer surfacer and refinish.
  • Or, apply waterborne primer surfacer, sand smooth and re-finish.
  • Or, apply acrylic lacquer primer surfacer thinned with non-penetrating thinner, sand smooth and refinish.

Lifting – Wrinkling, Raising, Alligatoring, Shrivelling, Swelling.

Identification: The existing paint film shrivels, wrinkles or swells during new finish application or drying. Wrinkling, often called lifting, is when an existing paint layer shrivels during the application of a new finish or as the new finish dries. This is caused by the solvents in the new finish attacking the old finish. You’ll most likely see this malady when recoating enamels or urethanes that are not fully cured, or if and when you exceed the maximum flash (dry) or recoat time during application. It’ll also sometimes happen when you recoat a basecoat/clearcoat finish where the old clearcoat had an insufficient film build.

Causes:

Solvents in a newly applied product attack the previous finish causing wrinkling, raising, or puckering of the paint film due to:

  • Recoating enamels or urethanes that are not fully cured.
  • Recoating a basecoat/clearcoat finish, where existing clearcoat has insufficient film build.
  • Exceeding maximum flash or recoat times during applications.

Prevention:

Check questionable finishes by rubbing a small inconspicuous area with a shop towel saturated with lacquer thinner. Finishes susceptible to lifting will soften, wrinkle or shrivel as lacquer thinner is applied. If any of these reactions occur, the following recommendations should be considered:

  • DO not exceed a products maximum recoat time before recoating or after application.
  • Allow enamels or urethanes to thoroughly cure before recoating or attempting a repair.
  • Avoid applying undercoats or topcoats excessively wet.
  • Use waterborne undercoats to repair extremely sensitive finishes.

Repair Process:

  • Remove areas lifted and refinish.

Loss of Gloss or Dieback

Identification: A noticeable loss of surface gloss.

Cause:

  • Incorrect mixing or contaminated hardener where no cross-link occurs.
  • Porous primer.
  • Poor flow primer.
  • Attack of primer by solvent from the topcoats.
  • Interrupted baking/uneven temperatures.
  • Certain metallic basecoats.
  • Topcoat applied too thin.

Prevention:

  • Use finer grade of sanding paper.
  • Increase film thickness/improve flow of topcoat.
  • Ensure adequate temperatures in cooler weather.
  • Do not interrupt baking cycle.
  • Allow adequate flash times, follow manufacturers application instructions.
  • Seal solvent-sensitive primers (e.g. lacquer).

Repair Process:

  • Buff and polish.
  • If extreme, sand and refinish.

Orange Peel

Identification: Uneven surface formation, texture like skin of an orange. One of the more common paint problems we run into, and its name is self-explanatory. It looks like an orange peel. This predicament is often caused by under-thinning/reducing the paint, spraying at too low a pressure, or a combination of both. Other causes may well be too fast a thinner or reducer, piling on too many or too heavy coats, or improper spray gun adjustment. Depending on severity orange peel can be repaired by compounding and polishing, or wet sanding with 1200 grit or finer paper and then buffing, or sanding and re-spraying the surface.

Causes:

  • Improper spraying pressure/technique or application temperatures.
  • Improper flash or recoat times between coats.
  • Extreme shop temperatures (When air temperature is too high, droplets lose more solvent and dry out before they can flow out and level).
  • Use of improper reducer/thinner (Fast evaporating solvents cause the atomized droplets to dry before they reach the surface).
  • Materials not mixed correctly.

Prevention:

  • Use proper gun adjustments, techniques and recommended pressures.
  • Schedule paint jobs to avoid extreme temperature/humidity conditions.
  • Allow proper dry times for undercoats/topcoats per manufacturers recommendations.
  • Use recommended thinners per manufacturers instructions.
  • Follow paint mixing instructions carefully per manufacturers recommendations.

Repair Process:

  • Sand and buff using a mild polishing compound for enamel, rubbing compound for lacquer.
  • In extreme conditions, sand to smooth surface and respray topcoat.

Peeling / Blistering / Adhesion Problems

Identification: Loss of adhesion between paint and substrate (topcoat to primer and/or old finish, or primer to metal).

Causes:

  • Improper cleaning or preparation of substrate.
  • Failure to remove sanding dust or other surface contaminants.
  • Improper metal treatment.
  • Use of incompatible materials or not properly mixed.
  • Condensation on substrate due to temperature changes.
  • Flash off/drying times too short.
  • Formation of condensation on substrate between coats due to temperature fluctuations.
  • Applying excessive film thickness or primers or basecoat.

Prevention:

  • Thoroughly degrease, clean and prepare surface carefully.
  • Use correct metal primer (e.g. self-etching or epoxy primer).
  • Stir all pigmented undercoats and topcoats thoroughly.
  • Keep to specified dry times.
  • Follow manufacturers application instructions.

Repair Process: Remove finish from an area slightly larger than the affected area and refinish.

Pinholing

Identification: Tiny holes in the finish, putty or body filler usually the result of trapped solvents, air or moisture.

Cause:

  • Improper surface cleaning or preparation – moisture left on primer-surfacers will pass through the wet topcoat causing pinholing.
  • Contaminated air lines (Moisture or oil in airlines will enter paint).
  • Incorrect gun adjustment or spray technique (Gun too close to substrate).
  • Improper dry method (Fanning a newly applied finish can drive air into the surface causing the surface to skin, which result in pinholes when solvents retained come to the surface).
  • Improperly primed body filler.
  • Improperly mixed polyester, fibreglass bodies.

Prevention:

  • Thoroughly clean all surfaces and ensure surface is dry.
  • Drain and clean air pressure regulator to remove trapped moisture and dirt. Air compressor tank should also be drained regularly.
  • Use proper gun adjustments, technique and pressure.
  • Allow sufficient flash and dry times. Do not dry by fanning.
  • Body filler should be sufficiently filled with primer-surfacer.
  • Body filler must be thoroughly mixed.

Repair Process: Affected areas must be sanded smooth and refinished.

Runs / Sags

Identification: Appears as a thick, raised uneven line on the surface.

  • Typically, on vertical surfaces.
  • May be in topcoat colour or clearcoat.

Causes:

  • Incorrect spraying viscosity, spray technique, flash off times between coats or film thickness.
  • Defective spray gun setup/incorrect pressure.
  • Temperature – shop/garage too cold.
  • Incorrect thinner/reducer/hardener used.

Prevention:

  • Do not ‘pile’ on finishes. Allow sufficient dry times between coats.
  • Use proper gun adjustments, techniques and gun pressure.
  • Warm material/substrate to room temperature.
  • Use correct hardeners, thinners.

Repair Process:

  • In clearcoat: sand and buff.
  • In basecoat: (Colourcoat or topcoat/clearcoat) Clean affected area and let dry until surface can be resanded and repainted.

If you do “sew some curtains,” in some cases you can wipe the area with a solvent-wetted rag and then clean and re-spray the area (seldom a first choice), or you can keep on going and wait till the paint fully cures and then sand and buff or sand and re-spray.

Solvent Popping

Identification: Blisters on the paint surface. Or boiling as it’s sometimes known, can be recognized by groups of small bubbles or crater-like openings in the paint surface.

Causes:

  • Poor surface cleaning and preparation.
  • Incorrect thinner/reducer, especially the material is sprayed too dry or at excessive pressure.
  • Spraying too much, too fast – excessive film build. Too heavy on undercoats may trap solvents causing popping or topcoat/clearcoat as solvent escapes.
  • Incorrect gun setup.
  • Booth with insufficient air flow.

Prevention:

  • Degrease and prepare surface carefully.
  • Apply at recommended film thickness.
  • Allow proper dry times for undercoats and topcoats. Allow each coat of primer-surfacer to dry naturally. Do not fan.
  • Check oven temperatures and follow manufacturers recommendations.
  • Do not ‘pile’ on coatings. Follow manufacturers recommended film thickness and flash times.

Repair Process:

  • After drying, repaint with sanding (within 24 hours).
  • If extreme, sand affected areas, refinish pinholes with a polyester filler, prime and refinish.

Please note the information provided in this website is General Information only, please read all product data sheets and safety data sheets before commencing any work. If pain persists show a professional.