How to fix common painting mistakes and make sure they don't recur

Fisheyes

Repair steps:

1. Wipe down the painted surface with a dry tack cloth to remove dust and dirt.

2. Dampen a clean rag in mineral spirits and wipe the surface again. A solvent cleaner removes any grease, wax buildup or oil (including skin oil). Make sure you clean the surface thoroughly since any surface contaminants will produce fisheyes in the clear coat.

3. Use a lint-free cloth to dry the cleaned surface (don't leave any dust or particles behind). Examine the entire surface you intend to clear coat to ensure there are no contaminants. If necessary, spot clean any contaminated areas.

4. Mix the recommended fisheye eliminator into the clearcoat. Be sure to follow the specific product instructions regarding application rates, as the amount of eliminator needed will differ for each product and the amount of finish you use.

5. Add any additional additives (for example, thinner) to the clear coat as required by specific product instructions. Read carefully since these requirements may change depending on the spray gun used and other factors.

6. Spray the clearcoat onto the surface in smooth, thin layers that also are even. Make overlapping passes by about one-half inch to avoid lines in the finish. Apply the necessary number of coats, allowing each coat to dry in between as recommended.

Prevention:

Always use hot water and detergent to thoroughly clean the area to be painted. When this is done, apply solvent cleaner and wipe with clean, dry rags.

Some shops are more prone to fisheye problems due to environmental issues related to oil and moisture contamination. If your shop does, address this problem by investing in an effective air filtering system capable of removing this contamination.

Lifting

Lifting occurs when the existing paint film swells, wrinkles or shrivels when a new finish is applied or as it dries. This happens when solvents in the new finish attack the older paint, often because the painter has ignored the recommended cure, flash, and recoat times. Lifting also happens when the painter doesn't wait to recoat with a basecoat or clearcoat until the existing clearcoat has a sufficient film build.

Repair steps:

• Remove the refinish materials and re-spray the area. Check the content of topcoat and substrate coatings or primers before reapplying the finish.

Prevention:

Carefully inspect every vehicle before applying a new finish. If you think a finish might be susceptible to lifting, test it by rubbing a small, inconspicuous area with a towel saturated with lacquer thinner. Suspect finishes will shrivel, swell or soften.

Though you always should adhere strictly to any product's application instructions, be more aware of the following when dealing with a suspect finish:

• Avoid incompatible materials, such as sealers and primers or using a thinner with enamel products.
• Do not simply pile on topcoats. Allow sufficient drying and flash times. Only apply the final topcoat when the previous coat is still soluble or after it has completely dried and is impervious to topcoat solvents.
• Select the correct reducer or thinner for the finish. Make sure it is suitable for existing shop conditions.
• Do not exceed recoat times during or after application.
• Allow urethanes and enamels to cure thoroughly.
• Use waterborne undercoats to repair extremely sensitive finishes.

Gloss loss (dulling or hazing)

Any finish can dull over time (Fig. 1) due to time and the elements. Premature dulling can be the result of:

• Insufficient film thickness clearcoat or topcoat color.
• Buffing or compounding before the paint has fully cured.
• Using too coarse of a compound (for example, rubbing compound)
• Surface poorly cleaned.
• Applying a topcoat on wet subcoat.
• Washing the finish with caustic cleaners.
• Insufficient curling/drying of undercoats before application of topcoats.
• Using a poor grade and/or too fast evaporating thinner/reducer for spray conditions.
• Insufficient air movement during and after application.
• Spraying over a solvent-sensitive or deteriorated substrate finish without proper sealing or priming.

Repair steps:

1. Let the finish cure thoroughly.

2. Compound or polish to restore gloss.

Dulling also may be repaired by sanding and refinishing the affected areas.

Prevention:

• Apply the topcoat according to product label directions using the recommended gun set-up and air pressure.
• Allow all coatings sufficient flash times between coats.
• Apply a sufficient number of coats to achieve recommended proper film thickness. If possible, check the thickness with a gauge.
• After using rubbing compound, follow by using a finer glazing compound.
• Never use hand-rubbing compound with a buffing machine.

Mottling

Also called spotting, tiger stripe or floating, mottling occurs only when the metal flakes float together to form a more silver appearance in the paint color. Mottling frequently is the product of poor spraying technique – e.g. tilting the gun, holding the gun too close to the work, utilizing an uneven spray pattern, improper (or omitting) use of mist coats or spraying product that is "too wet." Mottling also may be caused by using the wrong solvent (thinner or reducer), using materials that are not uniformly mixed or painting while the shop temperature is too low for the products used.

Repair steps:

1. Spray two medium coats of metallic color.

2. Apply a lighter third mist coat of color to help distribute the metal flakes evenly throughout the paint.

Prevention:

• Use the proper\recommended spray gun adjustments, techniques, and air pressure.
• Keep your spray guns clean (especially the air cap and needle fluid tip) and in good working condition.
• Adjust the gun for best atomization and balance the spray pattern before application.
• Mix all pigmented topcoats – especially metallics – thoroughly.
• Use the correct ratio of thinner/reducer.
• Allow the basecoat proper flash/dry time before applying the clearcoat.
• Select the paint solvent that is suitable for existing shop conditions. For example, in cold, damp weather use a faster drying solvent.

Peeling

Peeling (Fig. 2) occurs when adhesion is lost between refinish products (sealer, primer or topcoats). The different coats of paint products or materials separate and one peels off another. Possible causes include:

• Improper cleaning or preparation of a paint job. Keep in mind that failing to remove sanding dust and other surface contaminants will keep the finish coat from coming into proper contact with the substrate.
• Applying an incompatible undercoat to a specific substrate (e.g. plastics, aluminum, etc.).
• Failing to properly treat the metal.
• Failing to properly mix materials.
• Not using the proper sealer.

If peeling occurs in the clearcoat, possible causes include:

• Insufficient film thickness.
• Solvent cleaning the basecoat before applying the clearcoat.
• Sanding the basecoat before applying additional basecoat or clearcoat.
• Applying the basecoat or clearcoat while either is too dry.
• The basecoat thickness is excessive.
• Under or over reduction.

Repair steps:

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

2. Featheredge and refinish. Or,

1. Strip an area slightly larger than the affected area to the bare substrate.

2. Refinish.

Prevention:

• Thoroughly clean areas to be painted. Make it a shop practice to always wash the sanding dust off the area to be refinished with a cleaning solvent.
• Use the correct metal conditioner and conversion coating. For the best finish, plastic parts may require a special primer and flex additive.
• Mix all pigmented undercoats and topcoats thoroughly.
• Recoat all products within their recommended minimum and maximum recoat time.
• Apply a sufficient number of coats to obtain the recommended film thickness.
• In general, note that sealers are recommended to improve the adhesion of topcoats.
• Only use an adhesion promoter when specifically recommended.

Sanding scratches

Scratches typically appear because a shop either has sanded a single stage metallic finish prior to buffing or sanded a single stage or basecoat metallic prior to applying the clearcoat.

Repair steps:

Repairs are basic. Allow the finish to dry, then sand and refinish.

Prevention:

1. Avoid sanding basecoat finishes before applying a clearcoat. If sanding is necessary, apply any additional color following the product label direction.

2. When sanding single stage finishes, restrict work to minor imperfections (such as nib sanding in place of sanding entire panels). Use 1200 or finer grit sandpaper.

Orange peel

As its name suggests, orange peel is uneven surface formation that resembles an orange skin. Orange peel is the result of paint droplets drying out before they flow out and level smoothly together. This can be the product of:

• Improper flash or recoating times. If the first coat is allowed to flash too much, solvent in the paint droplets of subsequent coats will be absorbed into the first coat before the proper flow is achieved.
• Improper spray gun adjustment and technique. Wide fan patterns, too little air pressure and spraying at too great distances can cause paint droplets to be too dry when they reach the work surface.
• High paint booth temperature. When booth air temperature is too high, droplets lose more solvent than intended and dry before they can flow out and level properly on the body surface.
• Improperly mixing in too little reducer thinner or reducer. This can make the paint too thick, meaning it won't flow out smoothly, thereby causing orange peel.
• Using an incorrect reducer. Paint that is under diluted or thinned with a fast-evaporating

Reducer or thinner can develop atomized droplets that become too dry before reaching the work surface.

Repair steps:

Normally, applying two full wet coats of clearcoat, making sure to use the correct flash times between each coat, will repair orange peel.

If orange peel is relatively minor, shops can correct it by compounding or machine buffing after the finish has dried. Note: In some cases (particularly more severe ones), it may be necessary to wet sand the orange peel area before compounding.

Prevention:

• Thoroughly mix all pigmented topcoats and undercoats.
• Schedule painting to avoid temperature and humidity extremes. In addition, choose a reducer that is suitable for painting conditions. A slower evaporating reducer or thinner can prevent orange peel.
• Use recommended dry and flash times. Never dry by fanning.
• Use proper gun adjustments, techniques and air pressure.
• Reduce products to recommended viscosity with the recommended reducer/thinner.