Learn Auto Painting

Learn More About Auto Paint Repair Reactions -And How To Understand Them

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.

So don't worry, we all see these problems sometimes and in my book a "Professional" is not a person who doesn't make mistakes but a person that can correct the mistake that he has made. By you learning these reactions in automotive painting you'll soon understand what it takes to get PRO finishes all the time!

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.

Here our list of common paint problems, we'll expand on each topic in detail below:
Bleeding  - Original finish discoloring or color seeping through to the new topcoat color.
Blistering  - Bubbles or pimples appearing in the topcoat film, often months after application.
Blushing  - A milky white haze that appears on lacquer films.
Chalking  - Finish formation caused by pigment powder no longer held by binder, making a dull finish.
Chemical Staining - Spotty discoloration of the surface.
Chipping  - Small chips of a finish losing adhesion to the underlying layer (substrate).
Cracking  - A series of deep cracks running in no definite pattern.
Crazing  - Fine splits or small cracks that completely checker an area in an irregular manner.
Die Back - Loss of gloss after application.
Dirt  - Small bumps deposited in, on, or under the paint film.
Dry Spray - A rough, textured surface often confined to a small area.
Featheredge Splitting - Appears as stretch marks (or cracking) along the featheredge. Occurs during/shortly after topcoat is applied over lacquer primer.
Fish Eyes - Tiny surface finish blemishes that resemble small circles of popped paint bubbles, of fish eye appearance.
Gloss/DOI  - Poor Gloss Finish.
Lifting  - Surface distortion or shriveling, while the topcoat is being applied or while drying.
Line Checking - A series of parallel lines or cracks ranging from very short up to about 18 inches.
Micro-Checking  - Severe dulling of the film containing many minute cracks that do not touch.
Mottling  - Only in metallics when the flakes float together to form a spotty or striped appearance.
Orange Peel - Uneven Surface Formation - with an orange peel texture.
Overspray  - Paint materials from another unit falling on adjacent surfaces.
Paint Color Matching - Finished panels that don't match the color of standard panels.
Paint Runs and Sags - Heavy application of sprayed material failing to adhere uniformly to the surface.
Peeling Paint - Loss of adhesion between paint and substrate.
Pinholing  - Tiny holes or groups of holes in the finish or in putty or body filler.
Sand Scratches - Sanding pattern imperfections that show through the finished paint film.
Sandscratch Swelling - Enlarged sand scratches caused by swelling action of topcoat solvents.
Soft Paint - Easy to damage or penetrate paint film with fingernail.
Solvent Popping - Blisters on the paint surface caused by trapped solvents in the topcoats or primer.
Water Spotting - General dulling of gloss in spots or masses of spots.
Wet Spots - Discoloration and/or the slow drying of various areas.

Wrinkling  - Surface distortions/shriveling that occurs while enamel topcoat is being applied (or later during the drying stage.)

 

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.

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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.

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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

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 film build up (is it too low)
Check solvent selection.
Check heat during cure process (too low).
Check airflow during initial cure.
Check reduction ratio (over reduction).
Check for uncured undercoats.



Lifting

Condition : Surface distortion or shriveling, while the topcoat is being applied or while drying.

Causes

Use of incompatible materials. (Solvents in new topcoat attack old surface which results in a distorted or wrinkled effect.)
Insufficient flash time. (Lifting will occur when the paint film is an alkyd enamel and is only partially cured. The solvents from the coat being applied cause localized swelling or partial dissolving which later distorts the final surface.)
Improper dry. (When synthetic enamel type undercoats are not thoroughly dry, topcoating with lacquer can result in lifting.)
Effect of old finish or previous repair. (Lacquer applied over a fresh air-dry enamel finish will cause lifting.)
Improper surface cleaning or preparation. (Use of an enamel type primer or sealer over an original lacquer finish which is to be topcoated with a lacquer will result in lifting due to a sandwich effect.)
Wrong thinner or reducer. (The use of lacquer thinners in enamel increases the amount of substrate swelling and distortion which can lead to lifting, particularly when two toning or recoating.)

Prevention

Avoid incompatible materials such as a thinner with enamel products or incompatible sealers and primers.
Don't pile on topcoats. Allow sufficient flash and dry time. Final topcoat should be applied when the previous coat is still soluble or after it has completely dried and is impervious to topcoat solvents.
Select the thinner or reducer that is correct for the finish applied and suitable for existing work area conditions.

Solution : Remove finish from affected areas and refinish.


Line Checking

Condition : Similar to cracking , except that the lines or cracks are more parallel and range from very short up to about 18 inches.

Causes

Excessive film thickness.
Improper surface preparation. (Often times the application of a new finish over an old film which had cracked and was not completely removed.)

Prevention

Don't pile on topcoats. Allow sufficient flash and dry time. Do not dry by gun fanning.
Thoroughly clean areas to be painted before sanding. Be sure surface is completely dry before applying undercoats or topcoats.

Solution : Remove color coat down to primer and apply new color coat.


Micro-Checking

Condition : Appears as severe dulling of the film, but when examined with a magnifying glass, it contains many small cracks that do not touch.

Micro-checking is the beginning of film breakdown and may be an indication that film failures such as cracking or crazing  will develop.

Solution : Sand off the color coat to remove the cracks, then recoat as required.


Mottling

Condition : Occurs only in metallics when the flakes float together to form a spotty or striped appearance.

Causes

Wrong thinner or reducer: Check the reducing solvent and its viscosity.


Materials not uniformly mixed


Spraying too wet

- Check solvent selection.
- Check for excessively high fluid delivery.
- Check the equipment setup (fluid delivery).

Holding spray gun too close to work: 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).


Uneven spray pattern: Check your paint spray gun pattern.


Low Painting Area Temperature

- Check temperature in spray environment (too cool).
- Check temperature of unit being sprayed.

Alternatives


- 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 proper flash and dry times.
- Check if defect is specific to one color or many.
- Check atomizing air pressure.

Prevention

Select the thinner or reducer most suitable for existing painting area conditions.
Stir all pigmented topcoats - especially metallics thoroughly.
Use proper gun adjustments, techniques and air pressure.
Keep your spray gun clean (especially the needle fluid tip and air cap) and in good working condition.

Solution : Allow color coat to set up and apply a drier double coat or two single coats, depending upon which topcoat you are applying.


Orange Peel

Condition : Uneven Surface Formation - much like the physical appearance of orange peel. Results from poor coalescence of atomized paint droplets. Paint droplets dry out before they can flow out and level smoothly together.

Causes

Improper Gun Adjustment and Techniques

- Check for low air pressure.
- Check for wide fan spray patterns.
- 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. Spraying at excessive gun distances causes droplets to become too dry during their travel time to the work surface and they remain as formed by gun nozzle.
- Check the spray gun was setup properly using the correct tips and spray cap.

Extreme Painting Environment Temperature

When the air temperature is too high, droplets lose more solvent and dry out before they can flow and level properly. The ideal temp to paint at is 22.5 degrees centigrade.

Improper Drying

Gun fanning before paint droplets have a chance to flow together will cause orange peel.

Improper flash or re-coat time between coats

If the first coats of enamel are allowed to become too dry, the solvent in the paint droplets of following coats will be absorbed into the first coat before proper flow is achieved.

 Wrong and/or too little thinner or reducer

Under-diluted paint or paint thinner with fast evaporating solvents causes the atomized droplets to become too dry before reaching the surface.

Materials not uniformly mixed

Many finishes are formulated with components that aid coalescence. If these are not properly mixed, orange peel will result.

Alternatives

- Check the smoothness of the substrate surface.
- Check if the imperfection is specific to the one color.

Prevention

Use proper gun adjustments, techniques and air pressure.
Schedule painting to avoid temperature and humidity extremes. Select the thinner or reducer that is suitable for existing conditions. (The use of a slower evaporating solvent will overcome this.)
Always allow sufficient flash and dry times. Never dry by fanning.
Always allow proper drying time for undercoats and topcoats. (Not too long or too short.)
Select the thinner or reducer that is most suitable for existing environmental conditions to provide good flow and leveling of topcoat.
Reduce to recommended viscosity with proper thinner/reducer.
Stir all pigmented undercoats and topcoats thoroughly.

Solution : Compounding may help with removing orange peel from paint - a mild polishing compound for enamel, rubbing compound for lacquer. In extreme cases, sand down to a smooth surface and refinish, using a slower evaporating solvent at the correct air pressure.

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Overspray

Condition : Paint materials from another unit falling on adjacent surfaces.

Cause : Misdirected spray droplets or dry spray.

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 correct booth (work area) air balance and flow.
Check for sequence of panel application.
Check paint spray gun technique.
Check if defect is specific to one color.
Check air pressure (too high).
Check for over reduction.
 

Paint Color Matching

Condition : Finished panels that don't match the color of standard panels.

Cause : Variations in application and/or paint materials.

Suggested Corrective Action Checklist

Check other units to determine if a pattern is beginning to take place.
Check for complete hiding.
Check for variables in spray application.
Check lines and equipment for leftover contamination from previous color.
Check for improper mixing.
Check for proper agitation.
Check gun pattern.
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 that you setup the equipment correctly.


Paint Runs and Sags

Condition : Heavy application of sprayed material that fails to adhere uniformly to the surface.

Causes

Too much thinner or reducer: Check for excessive fluid delivery.


Wrong thinner or reducer

- Check the solvent selection is correct (not too slow).
- Check to see if the paint was reduced correctly.

Excessive film thickness without allowing proper dry time

- Check for excessive film build up.
- Check for too short flash (dry) time.
- Check for excessive application overlap.

Low air pressure (causing lack of atomization), holding gun too close or making too slow a gun pass

- 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 for insufficient air pressure.

Painting environment or surface too cold

- Check for low spray area temperature.
- Check temperature of unit.
- Check temperature of paint.

Prevention

Read and carefully follow label instructions. Select the thinner or reducer that is suitable for existing shop conditions.
Select proper thinner/reducer.
Don't pile on finishes. Allow sufficient flash and dry time in between coats.
Use proper gun adjustment, techniques and air pressure.
Allow vehicle surface to warm up to at least room temperature before attempting to refinish. Try to maintain an appropriate painting area temperature for paint areas.

Solution : Wash off the affected area and let dry until you can sand affected area to a smooth surface and refinish.


Peeling Paint

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

Causes

Improper cleaning or preparation: Failure to remove surface contamination such as oil, sanding residue, overspray, water, solvent cleaner residue and other surface contaminants will prevent the finish coat from coming into proper contact with the substrate.


Poor surface preparation prior to top coat application

- Check for non-sanding of substrate or primer application.
- Check for case hardening of substrate.

Materials not uniformly mixed

- Check for incompatible products.
- Check for a proper film build up.

Failure to use proper sealer

- Check solvent selection is correct (not too fast).
- Check for thin sealer film builds or no sealer.

 Alternatives: Check for masking tape contacting the painted surface.

Prevention

Thoroughly clean areas to be painted. (It's always good practice to wash the sanding dust and any surface contamination off the area to be refinished). Use wax and grease remover prior to applying top coats and the use of a tack cloth just after using wax and grease remover will help to pick up very fine particles of lint, dust and other debris.
Use correct metal conditioner and conversion coating.
Stir all pigmented undercoats and topcoats thoroughly.
Use sealers to improve adhesion of topcoats.

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


Pinholing

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

Causes

Improper surface cleaning or preparation. (Moisture left on primer will pass through the wet topcoat to cause pinholing.)
Contamination of air lines. (Moisture or oil in air lines will enter paint while being applied and cause pinholes when released during the drying stage.)
Wrong gun adjustment or technique. (If adjustments or techniques result in application which is too wet, or if the gun is held too close to the surface, pinholes will occur when the air or excessive solvent is released during dry.)
Wrong thinner or reducer. (The use of a solvent that is too fast for work area temperature tends to make the refinisher spray too close to the surface in order to get adequate flow. When the solvent is too slow, it's trapped by subsequent topcoats.)
Improper dry. (Fanning a newly applied finish can drive air into the surface or cause a skin dry - both of which result in pinholing when solvents retained in lower layers come to the surface.)

Prevention

Thoroughly clean all areas to be painted. Be sure surface is completely dry before applying undercoats or topcoats.
Drain and clean air pressure regulator daily to remove to remove trapped moisture and dirt. Air compressor tank should also be drained daily.
Use proper gun adjustments, techniques and air pressure.
Select the thinner or reducer that is suitable for existing work area conditions.
Allow sufficient flash and dry time. Do not dry by fanning.

Solution : Sand affected area down to smooth finish and refinish.

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Sand Scratches

Condition : Objectionable sanding pattern imperfections that show through the finished paint film.

Cause : Imperfections due to soft primer, improper sanding techniques and low top coat film build. Excessive film builds with improper flash times.

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 defect is specific to one or many colors.
Check for correct sandpaper grit (too coarse).
Check topcoat film thickness.
Check for proper feathered edge technique.
Check for uncured primer.
Check for poor quality solvent used in undercoats.
Check for proper flash and dry times.
Check for excessive primer film builds.
Check for proper paint spray gun technique and atomization.
Check for under reduced primer (bridging scratches).
Check for sanding before primer is cured.
Check for film builds of sealer or no sealer.


Sandscratch Swelling

Condition : Enlarged sandscratches caused by swelling action of topcoat solvents.

Causes

Improper surface cleaning or preparation. (Use of too coarse sandpaper or omitting a sealer in panel repairs greatly exaggerates swelling caused by thinner penetration.)
Improper thinner or reducer (especially a slow-dry thinner or reducer when sealer has been omitted.)
Under-reduced or wrong thinner (too fast) used in primer causes 'bridging' of scratches.

Prevention

Use appropriate grits of sanding materials for the topcoats you are using.
Seal to eliminate sandscratch swelling. Select thinner or reducer suitable for existing work area conditions.
Use proper thinner and reducer for primer.

Solution : Sand affected area down to smooth surface and apply appropriate sealer before refinishing.


Soft Paint

Condition : Easy to damage or penetrate paint film with fingernail.

Cause : Insufficient cure of 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 for improper film build up.
Check hardener (old, improper or contaminated).
Check for improper mixing ratio.
Check for improper heat during cure (drying) time.
Check for improper airflow.
Check flash or dry times.
Check solvent selection (not too fast).
Check for excessive humidity.
Check for cool spray area temperature.


 

Solvent Popping

Condition : Blisters on the paint surface caused by trapped solvents in the topcoats or primer - a situation which is further aggravated by force drying or uneven heating.

Causes

Improper surface cleaning or preparation

- Check other units to determine if a pattern is beginning to take place.
- Check if the imperfection is on the whole unit or in a specific area.
- Check if defect is specific to one or many colors.
- Check if defect is most prevalent on horizontal surfaces.

Wrong thinner or reducer

- Use of fast-dry thinner or reducer, especially when the material is sprayed too dry or at excessive pressure, can cause solvent popping by trapping air in the film.
- Check for correct reducing solvent.

Excessive film thickness

- Insufficient drying time between coats and too heavy application of the undercoats may trap solvents causing popping of the color coat as they later escape.
- Check for excessive film build up.
- Check for high fluid delivery.
- Check for high viscosity.
- Check for too much overlapping in film build.
- Check for proper flash and purge times.

Alternatives

- Check for high temperature in first part of force dry.
- Check for low air pressure.

Prevention

Thoroughly clean areas to be painted.
Select the thinner or reducer most suitable for existing painting area conditions.
Don't pile on undercoats or topcoats. Allow sufficient flash and dry time. Allow proper drying time for undercoats and topcoats. Allow each coat of primer to flash naturally - do not fan.

Solution : For refinishing solvent popping, if damage is extensive and severe, paint must be removed down to undercoat or metal, depending on depth of blisters; then refinish. In less severe cases, sand out, re-surface and re-apply topcoat.

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Water Spotting

Condition : General dulling of gloss in spots or masses of spots.

Causes

Water evaporating on finish before it's thoroughly dry.
Washing finish in bright sunlight.

Prevention

Do not apply water to fresh paint job and try to keep newly-finished car out of rain. Allow sufficient dry time before delivering car to customer.
Wash car in shade and wipe completely dry.

Solution : Compound or polish with rubbing or polishing compound. In severe cases, sand affected areas and refinish.


 

Wet Spots

Condition : Discoloration and/or the slow drying of various areas.

Causes

Improper cleaning and preparation.
Improper drying of excessive undercoat film build.
Sanding with contaminated solvent.

Prevention

Thoroughly clean all areas to be painted.
Allow proper drying time for undercoats.
Wet sand with clean water.

Solution : Wash or sand affected areas thoroughly and refinish.


 

Wrinkling

Condition : Surface distortions (or shriveling) that occurs while enamel topcoat is being applied (or later during the drying stage.)

Causes

Improper dry. (When a freshly applied topcoat is baked or force dried too soon, softening of the undercoats can occur. This increases topcoat solvent penetration and swelling. In addition, baking or force drying causes surface layers to dry too soon. The combination of these forces causes wrinkling.)
'Piling on' heavy or wet coats. (When enamel coats are too thick, the lower wet coats are not able to release their solvents and set up at the same rate as the surface layer which results in wrinkling.)
Improper reducer or incompatible materials. (A fast-dry reducer or the use of a lacquer thinner in enamel can cause wrinkling.)
Improper or rapid change in work area temperature. (Drafts of warm air cause enamel surfaces to set up and shrink before sub-layers have released their solvents, which results in localized skinning in uneven patterns.)

Prevention

Allow proper drying time for undercoats and topcoats.
Don't pile on topcoats. Allow sufficient flash and dry time.
Select proper reducer and avoid using incompatible materials such as a reducer with lacquer products or thinner with enamel products.
Schedule painting to avoid temperature extremes or rapid changes.

Solution : Remove wrinkled enamel and refinish.

 

I Thank You for checking out this page and really hope that it has opened your eyes about some of the most common problems faced when getting started with auto body and paint.

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Tony Bandalos