Despite of our best intentions, paint defects sometimes emerge. The key to successful repairs is the approach used to correct the problems.

Even techs who are performing quality paint work occasionally have to deal with dissatisfied customers. And dealing with the customer sometimes brings you in touch with a highly dreaded refinishing demon—the paint comeback. This is when your refinishing work has not satisfied the customer’s desire for quality. This malady negates even quality body repair and highlights the need for a new approach to refinishing quality control.

Prevent bleed-through of materials and colors by using a sealer between the old surfaces and the new coatings. Failure to do so may mean that correction is needed by removal of the new finish, primer/surfacer use and refinishing.

Poor topcoat adhesion over repaired surfaces can be thwarted by using quality primer-surfacer. Use a surfacing material that is chemically compatible with your refinishing products.

Start at the finish
First examine the refinishing defect with an attempt to isolate the cause. Inspect the surface closely. Ask yourself important questions, such as, “Has your shop experienced similar complaints with refinishing efforts?” You see, the best cure for paint problems is preventing them in the first place. For example, a common complaint is dirt in the finish. The cause of dirty surfaces range from inadequate paint preparation, poorly maintained booth filters, poor booth sealing and shop air circulation. But also, are technicians working cleanly enough? Are you using a poor grade of masking paper? Is your spraygun adequately cleaned? Are finishes skinned over so the surface is dust-resistant before being taken from the spraybooth? Answer these questions before new problems arise.

Know that to keep dirt minimized during refinishing, you must blow off doors, jambs, windows, hood and trunk openings, moldings, and wheel openings. Use a tack rag to wipe surfaces. Keep the vehicle in a clean drying environment so dust particles cannot stick on tacky surfaces. Make sure that booth technicians wear lint-free clothing during refinishing.

As well, a failure to strain material often causes a gritty finish. Other causes are improper stirring, using old materials and improper solvents. Find the source and correct these errors before more jobs are affected. Then you can refinish the customer’s defective surface.

Air Trapped?
Are you sure it’s dirt? Look closely. Small craters in the paint film present themselves if air bubbles are trapped in the wet paint film. These rise to the surface and burst. Improper spray gun setup, speed or surface distance during spraying can cause this. Occasionally you can sand these craters with 1,200 grit or finer sandpaper, then compound and polish to restore gloss. If not, sand to smooth and refinish the panel.

Do the craters look like fisheye?  These are small circular, crater-like openings that appear during or shortly after the spray application. Spraying over surfaces that are contaminated with oil, grease, silicone and wax typically causes fisheye. Sometimes using thinners as a cleaning solvent also causes fisheye. If the paint has dried, sand it to a smooth finish to eliminate the fisheye and refinish. To prevent future occurrences, clean the surface with detergent and hot water, followed by the recommended cleaner. Wipe with clean tack rags to dry. Lastly, use a fisheye eliminator that is specifically recommended for the topcoat.

Profit Runs Away?
Paint runs, sometimes called hangers or curtains, are finish coats that fail to stick. There are many causes. First, you may be applying paint materials upon coats that are too wet, or coats without proper flash time between each application. You may move the gun too closely, or slowly, and runs may occur. Also, runs can happen if you overlap the patterns too tightly, spray using too low pressures or use an unbalanced spray pattern. Using a slowly evaporating thinner/reducer or too cold of a booth and vehicle surface temperature may cause this trouble.

If caught when the paint is wet and near a bottom edge, many painters may try to make the coating run to a lower edge and wipe off the excess. But this is difficult and often unsuccessful.

If a refinish job has runs, try removing excess paint by block sanding with 1,200 grit or finer sandpaper. Finally, compound and polish. Remember however, if it’s basecoat/clearcoat, don’t sand the run down into the basecoat.

Giving a Lift?
Lifting occurs as solvents in your new coating attack the previous finish. While lifting is rarely a problem when repairing OEM finishes, if the panel being painted was previously refinished, you may experience a problem. Also, lifting occurs if you refinish enamels or urethanes that are not fully cured. The same may happen if you apply a flash or recoat when exceeding the maximum flash or recoat times, or an insufficient clearcoat film build occurs.

To help avoid lifting, follow some sound advice: Use a sealer as a barrier between the old and new finishes. When applying new primer/surfacers over soluble finishes, coat the complete panel. And if needed, use waterborne undercoats to repair extremely sensitive finishes.

Wrinkles Showing?
Wrinkling or shriveling of a finish, resembling the skin of a prune, happens when you pile on heavy, wet coats. This trouble, however, can also be created by spraying in hot and humid conditions, using too fast of a thinner/reducer, or putting a vehicle out in the hot sun too soon. And certainly, low spraygun air pressures and force-drying enamel without the recommended additives can also create this malady. If the surface is dry and trouble is slight, try lightly sanding the top surface until smooth. Allow the surface to cure and refinish.  If the defect is severe, however, remove the topcoat from the wrinkled area and refinish it.

Dry or Bumpy Coat?
Poor topcoat flow, often called orange peel, can be caused by under reduction, low spray air pressures, too fast of a thinner or reducer, and heavy coats. To cure the problem, compound or polish to reduce the surface texture. If needed, sand smooth with 1,200 grit or finer sandpaper, then compound and polish to restore gloss. If this fails, sand the finish smooth and refinish. However, if you go through the clearcoat, strip to the undercoat and refinish.

Color Stray?
Does a color bleed through? Experience teaches us that certain colors have less ability to cover undercoats. Solvent in the new topcoat sometimes dissolves soluble dyes or pigments in the original finish. This allows seepage into the new topcoat. To repair this malady, allow color to cure, then isolate the two with a sealer and refinish.

Many technicians get into refinishing trouble with the solvents they choose. Many finish problems begin simply because of a failure to follow the paint system manufacturer’s solvent recommendations.  Improper solvent choice causes poor gloss and adhesion, dullness, chalking, cracks or splits, blisters, sanding swell, or blushing.

Note that blushing or a milky finish can appear when moisture condenses in or on the paint film. Occasionally, to correct a blush after refinishing, you can apply heat to the affected area or add retarder and apply additional coats. If the finish has thoroughly dried, however, minor blushing may be corrected by compounding or polishing. Severe blushing requires sanding and refinishing. Remember that humid weather causes blushing. Avoid painting on damp days unless atmospheric conditions can be changed in the booth with infrared heaters. Choose a thinner/reducer to match spraying conditions. Be cautious as you make temperatures adjustments. Fast-drying solvents may lighten a color.

In most cases, be sure of mixture proportions and don't over-reduce the materials. Paint manufacturers often suggest using a viscosimeter to get the paint to proper consistency. Most finishes today are multi-stage basecoat/clearcoat, thus a mixing viscosimeter becomes a necessity for proper results.

Coatings manufacturers provide formula information to a car maker’s color standards and many variants. We know, however, that today's vehicle production and multiple-stage paint systems can create differences that may drastically affect the color match. Also, when we refinish, OEM surfaces have aged, and daily temperatures, humidity, paint spray viscosity, barometric pressures and other influential refinishing conditions change. These changes can cause mismatch.

Paint material manufacturers answer this trouble with major mixing, tinting and blending systems. But, before you grab a base color can from a paint mixing system to correct mismatch, realize that improper refinishing techniques may have caused your failure to match the OE finish. Examine a back-to-basics approach if, job after job, it becomes a mismatch problem. Ensure that proper air pressures exist and use the spraygun at the required height from surface. Maintain proper booth temperatures, and allow sufficient flash-time between coats. Do not buff or polish a surface until the paint is dry.

Also, use a test panel to evaluate color under multiple light sources other than shop lighting. Then adjust the color as needed. If color is close, tint, and then blend into an adjacent panel. Now remember, first view the color at equal gloss. You must compound or polish the old surface to comparatively match the new.

After a few weeks, some finishes may begin to chalk. But excess chalking can come from improper stirring of materials, improper thinner, exposure to chemical fumes and long exposure to the sun. 

Poor Cover?
If the coating does not hide, the color was probably not mixed properly with a thinner or reducer. Or perhaps the substrate or primer/surfacer was not uniform in color and a sealer was not used. To correct the condition, remove the coatings, seal and refinish with proper reduction until hiding is achieved.

Occasionally a recently refinished vehicle will have a coating that remains soft, and fingerprint or water spots appear. This may be from applying excessively wet coatings, or too little dry time between coats. Also, improper thinner/reducer or hardener may cause softness. In urethanes, improper mixing of catalyst driers may work to keep them soft. If so, removal of the finish and a redo are needed.

Using a spray gun that gives an unbalanced spray may cause an uneven distribution of metallic flakes. Tilting the gun, improper spray overlap and too close of a tip distance, and omission of mist coats can also cause this mottling. Metallic mottling can be created from too much thinner/reducer, or a clearcoat applied to a basecoat that has not thoroughly flashed.

If color is off, and the coating is still wet, sometimes you can correct single stage metallic finishes with a higher pressure mist coat. If it is two-stage, allow the basecoat color to flash, then apply a corrected low-pressure mist basecoat. But, avoid sanding the basecoat finishes before clearcoating.

Cracking or Sanding Marks?
If the vehicle has been out of the shop for a time, cracks or lines of various lengths and widths in the topcoat finish may appear, resembling dried mud. These may be due to excess film thickness, previously razed/cracked surfaces, insufficient flash time, force drying with the spray gun, or too much hardener. Also, poor paint mix, prolonged exposure to sunlight, moisture and extreme temperatures can add to the problem. However, these are not sanding tracks. Using poor thinners, reducers or hardeners contribute to this cracking. If cracking occurs, we recommend stripping to remove all products and do a refinish again.

No Shine?
Flattening or dulling may be created by wax, oil or grease on the old surface. But also know that inferior solvents can easily cause this trouble. Other causes can be insufficient flash time between coats; excess thinning; compounding too soon; and improper drying room ventilation. If compounding doesn't remove the dullness, the area will have to be sanded to the undercoat, then dressed in new primer-surfacer before refinishing. 

Environmental?
Water spots are circles with raised edges occurring when water contacts a finish that is not dry or cured. If these spots are present, first try wiping the surface with a damp cloth. Next, compound or polish. However, it may take judicious use of some 1,500- to 2,000-grit wet sandpaper, then some compound and polish to restore gloss. But remember, do not go through a clearcoat! If this light sanding won’t do it, then refinish it.

If irregularly shaped etching, pitting or discoloration occurs, be aware that harmful environmental contaminants may be the cause. These include tree sap, acid rain, bird droppings and road tar. To fix, try washing the vehicle first with soap and hot water, then rinse and dry. Next, clean with the appropriate solvent or surface cleaner. Some shops recommend a blend of a quart of water and a touch of baking soda. Afterward, compound the surface and polish to restore gloss. If a simple wash and polishing won’t remove the damage, try wet sanding with 1,500- to 2,000-grit wet grade sandpaper, then compound and polish.

If refinishing is necessary to correct the spots, sand to remove the finish of the damaged area with appropriate grit sandpaper, wash with a baking soda solution, then refinish. In severe cases, remove the damage to bare metal.

Blistering may occur months after the work is done, caused by moisture trapped beneath the paint. The cure is a complete removal of topcoat product and refinishing. First move to bare substrate before refinishing.

Finally, a loss of adhesion or separation of the paint film from the substrate is what we call peeling. Some of the causes are improper substrate prep, drying times, incompatible products, excessive basecoat film and improper film reduction. To fix separation, remove the area’s finish to the substrate, then featheredge and properly refinish.

Tracking problems
Quality control is critical in the paint shop. Defects will arise from time-to-time and should be tracked on a regular basis. To help improve overall performance, you should keep a record of problems as they occur to spot deficiencies in either product or technician performance. Any trends you find through this tracking will point towards improvements that will increase quality and customer satisfaction while reducing costly redos.