On this page, we list the most common painting problems that occur at body shops. Click on a defect to see its description and the ways to eliminate it and - above all - to learn how to prevent it.
Download the manual, complete with painting defects, to view it offline.
Evident stain due to a soluble dyestuff.
- Use of soluble pigments. - Reaction of the putty’s peroxides with dyestuffs or pigments present in the paint film. - Bitumen or tar residues
Insulate the damaged parts. In particularly serious cases sand until bare metal and restart the correct paint process.
- Effect the solvent test to verify the possible presence of soluble dyestuffs. - Verify the correct putty's hardener and peroxide dosage. - Ensure that all possible tar or bitumen residues have been removed.
The freshly-applied top coat shows local discoloration and/or yellowing in the points previously treated with polyester putty.
Too much hardener (peroxide) added to the polyester putty.
After the film is fully hardened: - Sand thoroughly to the surface of the putty. Apply a sealer and re-spray the final coat.
- Use the correct mixing ratios (showed in the data sheet), and mix the components in the correct way into an homogeneous mass. - Use the dispenser measuring correctly the mixing ratios, or operate by weight with the scale.
The painted surface displays more or less small pimples.
Blistering is caused by moisture or contamination under the paint due to: - Moisture absorption from the substrate (especially from put-ties and fillers) before painting. - Moisture condensation on the substrate created by a sudden change in temperature (e.g. the hot car straight out of the oven into a cooler room.). - Contamination of the substrate by water, grease, oils, etc. - Use of incompatible products or unsuitable thinners. - The painted surface, before complete through drying, was exposed to a high level of moisture or rain. - Thinning of water-borne product with tap water (contains mineral salts). - Presence of water in the compressed-air line.
After drying through of the film control the depth of the pimples: - If these are between the final coat and the underground, sand to reach a completely smooth surface, then re-coat. - If the pimples are between the substrate and the undercoat, sand thoroughly, clean accurately and repeat the complete paint system.
- Ensure the surface is thoroughly cleaned before any operation(use compressed air and silicon remover degreaser) - Protect the surface before the paint application and immediately after, to avoid moisture condensation. - Use experimented paint cycles to avoid any incompatibility. - Control the compressed air supply to eliminate any trace of oil, fat or water. - After wet sanding allow water to evaporate. - Dry-sand only polyester putties.
Bubble-shaped irregular swellings.
BUBBLES - Due to corrosion. - Due to drying. - Due to air trapping.
Due to corrosion: 1. Mechanical damage on the painted surface with subsequent humidity infiltration. 2. Insufficient preliminary substrate pre-treatment or incomplete anti-rust treatment. 3. Rust formation on sanded or damaged surfaces. 4. Insufficient panel sealing.
Due to drying: 1. High film thickness. 2. Too fast hardeners and/or thinners. 3. Too short flash-off. 4. Too high IR temperature. 5. Too short flash-off in wet-on-wet process.
Due to air trapping: 1. Insufficient putty or priming coat application. 2. Insufficient flash off time between primer and topcoat. 3. Air pockets in the priming coat due to unsuitable thinner. 4. Too high drying temperature
Sand until underlying layers by removing bubbles and/or rust. If necessary, apply an anticorrosive primer as soon as possible in order to avoid further corrosion phenomena.
- Repair the damaged points immediately and apply an anticorrosive primer in order to avoid corrosion. - Apply the recommended paint layers, use hardeners and thinners as indicated on the technical data sheet, follow the drying times, in order to avoid drying bubbles.
Deterioration of paint film due to binders/pigments decomposition on the painted surface.
- Incorrect hardener and/or mixing ratio. - Incorrect film thickness. - Deterioration due to weathering. - Incorrect technique applied
If the damage is very small, try to restore by polishing with abrasive paste, otherwise it is necessary to repaint.
- Use hardeners indicated on the technical data sheet. - Pay attention to the applied layers. - Effect a careful periodical maintenance.
The surface presents different colour shades (edges, lower panels).
1. Poor hiding power, depending on insufficient film thickness due to: - Unsuitable application techniques, especially in the least accessible zones. - Too few coats applied. Insufficient or non uniform coats. - Low covering colour requiring a specific coloured undercoat. - Incorrect mixing ratio and/or low viscosity. 2. Too short flash-off between coats or before the clearcoat application. 3. Thick or thin basecoat application
- Sand slightly and recoat. - If the haloes appear by spraying, spray in a uniform way.
- Use appropriate application techniques to reach a correct film thickness on the whole surface. - Apply a coats-number as indicated in the data sheet. - Always control if the finishing coat needs a coloured underground: if the case always apply the specific coloured undercoat. - Always stir paint thoroughly and filter it before application.
Loss of adhesion of the putty from the substrate.
- Incorrect substrate pretreatment. - Use of a wrong type of putty/stopper (e.g normal putty on zinc coated iron). - Wrong mixing ratio with the hardener. - Incorrect IR drying (too near lamps, too long a drying time). - Too high lamp temperature
Strip to bare metal and repeat the cycle.
- Use universal putties that can offer a good adhesion to all substrates. - Read the data-sheet and observe mixing ratio (depending on the room temperature), drying time, use of IR lamps. - Sand and clean the substrate following the prescriptions of the data sheet.
Paint repelled by contaminant forms craters like depressions with relief edges. Inspection with lens may reveal a small impurity at the base.
- Incorrect use of antistatic cleaning cloths that can contaminate the substrate. - The spray booth and/or the substrate are contaminated with silicone. - Contaminated compressed air (presence of water, oil,grease, wax). - Solvent contaminated spray gun when using water-borne products
Allow the film to harden: - Remove by sanding the affected paint, clean accurately and re-spray. - If the paint still forms craters, add a specific anti-silicone to it.
- Clean and degrease the substrate thoroughly before spraying the nex coat, using specific ANTI-SILICONE solvent. Remove the solvent with clean cloths before it can dry. - Check the spray booth filters and the oil/water separator and drain if necessary. - Alwais check the surface before spraying next coats; if necessary operate as indicated above. - Use only spray equipments perfectly clean. - Don't use products containing silicone in the spray booth. - Clean with suitable solvents and allow spray guns to dry when using water-borne products.
The colour shade of the repaired area does not match the cars original colour.
- Original car finish does not correspond with the mixed colour. - The mixed colour was obtained using pigments different from the original ones: metamerism. - Mixing colours have not been stirred enough. - Irregular spraying technique (number of coats, gun adjustment). - The spray check was carried out in incorrect light. - The test panel was sprayed incorrectly
After through drying of the film: - Sand the repaired section, mix the colour again, compare a test panel and re-apply the colour.
- Use correctly the colormap and the other helps offered by the Color-System. - In any case, before painting the substrate, always spray with the same spray gun as of the final application a test panel using the correctly catalysed and thinned product, with the same spray gun of the final painting and the same spray technique. Check the colour under different visual angles and different light sources. - Use the recommended prescriptions indicated in the data sheet. - Always mix accurately the paint and filter it before spraying. - Mix the paint carefully and always filter before applying it, by using compatible filters (in the spray gun too) with the aluminium particles size.
The edge of an underlying coat of the system can be seen in the topcoat underlining low gloss zones.
The bodyfiller has been applied incorrectly due to: - Too thick film thickness and too short drying times. - Unsuitable/ too fast hardener or wrong mixing ratio. - Airdrying in high humidity. - The undercoat was applied on old paint etc without correct sealing
After drying through of the film: - Sand with fine paper and polish. - If more serious, the surface must be sanded and re-sprayed.
- Apply the undercoat in the suggested in the data sheet film thickness and respect the drying time. - By low temperature and high humidity let dry in oven. - Always check the old paint films and if necessary apply a suitable undercoat.
Small holes on the surface of the undercoat.
- Incorrect use of antistatic cleaning cloths that can contami nate the undercoat surface. - The spray booth and/or the surface to paint are contaminated with silicone. - Contaminated compressed air supply (presence of water, oil, wax). - Solvent contaminated spray gun when using water-borne products. - Air absorption. - Use of unsuitable thinners and/or hardeners. - Wrong drying times (without following the indicated times)
After the through drying of the film: - Sand the cratered paint coat to eliminate any defect. Clean and degrease thoroughly with anti-silicone solvent, then apply a new coat.
Degrease the substrate thoroughly before spraying, using the specific ANTISILICONE solvent. Remove the solvent with clean cloths before it can dry. - Check the spray booth filters and the oil/water separator and drain if necessary. - Alwaiy check the surface before spraying next coats; if necessary operate as indicated above. - Clean with suitable solvents and allow spray guns to dry when using water-borne products.
Dust or dirt particles trapped in the dried paint.
- The surface was not clean enough. - The spray booth is not dust free (clothing creates dust). - Filters are dirty or clogged. The airline is dirty. - The paint is contaminated. - Ineffective paint filtering.
After through-drying: - Remove dirt by fine sanding (P1200), then polish. - If the dirt has been trapped deep into the paint, sand the surface and re-spray.
- Thoroughly clean the surface (by air and antistatic degreasing agents). - Keep the spray booth clean and wear fibre-free, antistatic overalls. - Replace the filters regularly. - Store the paint in tins that are clean and well sealed. Filter the paint every time before pouring it into the spray gun pot. - After use, thoroughly clean used equipment, especially the gun, and dry it with clean cloths.
Some points of the painted surface present insufficient gloss.
Insufficient drying time of the undercoats. - Use of too aggressive thinners. - Use of inappropriate hardeners. - Too slow drying with excessive humidity. - Low baking with insufficient air recirculation. - Exposure of the painted substrate not yet through dried, to weathering and/or aggressive chemical agents
After through drying of the film: - Polish using an abrasive compound according to the degree of gloss. - If polishing does not restore the gloss, flat with abrasive paper, then re-spray.
- Always follow the data-sheet prescriptions, apply the undercoats in the suggested film thickness, allowing adequate drying time between all coats. - Respect the baking temperatures for undercoats and finishing coat, in well aerated oven, expecially in case of low room temperature and high humidity. - Avoid to expose the painted surface to any aggressive in the first days after the painting.
Opalescent haze formed on the paint film surface.
Humidity/condensation trapped in the paint. This may be caused by the following: - Less favourable climate conditions. - Unsuitable thinners. - Incorrect air pressure. - Using more forced drying than recommended
Polishing could remove the defect. If this operation is insufficient, sanding with subsequent repainting is needed. If even after repainting this phenomenon reappears, verify the application conditions (spray gun adjustment, ventilation, drying temperatures).
- Avoid the application in critical climate conditions (strong humidity, loo low temperatures). - Use thinners recommended on the technical data sheet. - Avoid to force drying more than foreseen on the technical data sheet. - Ensure the environment is suitably air-conditioned (suitable temperatures und relative humidity).
Some aluminium particles appear in vertical orientation in the finishing coat.
Inappropriate application of the metallic matt base coat i.e. - Poor spray gun technique (e.g. dry spray). - Use of inappropriate spray gun (air cap, air pressure) and/or spray gun too far from surface. - Insufficient clearcoat film thickness to cover the aluminium flakes (expecially with “magnum size” coarse particles).
After through drying of the clear: sand with P800 grit paper and apply a new coat of clear.
- Always follow the prescriptions of the data sheet and use the indicated spray techniques. - Check the adjustment of the spray gun (nozzle, yield, air pressure). - In touch-ups or complete paint use specific blenders.
The fresh paint shows local colour differences: after spraying the metallic colour coat, light and darker spots (clouds) appear.
Improper application technique, i.e. - First coat is too wet with a dry grip coat on the top. - Incorrect adjustment of the spray gun (air cap, air pressure). - Incorrect spray viscosity. - Insufficient stirring of the paint
- Before applying the clear, apply a new uniform slight coat of the matt base, as indicated on the relevant technical data sheet. - If the clouds show after the application of the clear, sand the surface and re-spray (base coat + clear).
- Follow accurately the prescriptions in the data sheet. - Check the adjustment of the spray gun. - Stir accurately the thinned base colour and filter it before spraying. - Use the thinners indicated in the data sheet only.
The painted surface presents poor flow and resembles orange peel.
Poor flow due to: - Poor spray gun technique (gun held too far from the surface, causing the paint to dry). - Unsuitable spray gun adjustment (air cap, air pressure, etc). - Too high spray viscosity. - Use of too fast or unsuitable thinners. - Too short flash off between coats. - Too high surface temperature and/or spray booth temperature. - Application of too thick or too thin coats.
After the paint is thoroughly hardened: - Rub out orange peel with very fine abrasive paper and polish. - In severe case flat thoroughly and re-spray.
- Always follow the data-sheet prescriptions and observe the suggested spray gun techniques. - Use the suggested thinners depending on the room conditions, check the spray viscosity and the air pressure. - Apply uniform coats and respect the flash off time between the coats. - Check the room conditions: temperature and ventilation.
Atomized and dried paint particles that have settled on the surface during painting and not completely absorbed into the surface.
Insufficient overspray absorption due to wrong hardener and/or thinner as regards environmental conditions.
Sanding and re-application in respect to correct conditions.
- Mask carefully the panels that are not to be painted. - Consult the technical data sheet for suitable thinners or hardeners.
Small or large areas of a layer detaches itself from the substrate or from previous layer.
The paint is affected by forces that prevent adhesion. Loss of adhesion due to: - Presence of wax, fat, silicone, oil, or other releasing agents. - Inadequate surface adhesion. - Unsuitable temperature during application. - Incorrect film thickness
Remove loose paint layers and re-apply the system.
- Check accurately the substrate and choose a suitable paint system. - Pre-treat suitably the substrate. Consider that sanding and sand-blasting increasing the contact surface improve the adhesion. - Degrease accurately to remove any contamination that can reduce the wetting of the substrate by the new coat. - Check the spray viscosity: lower viscosity increase the wetting of the substrate and improve the adhesion. - Observe the flash-off time indicated in the data sheet between the layers of the paint system. - In two-coats system (basecoat + clear) the oven drying improves a better adhesion between the coats. - Avoid mixed cycles by using products of different paint manufacturers.
Small deep holes in the paint surface: observing accurately one can see the paint layer in which the hole originated (sealer or putty).
Penetration of the final coat from holes due to air trapped in the application. - Incorrect application of the filler (sanding, sealing, etc.) - Too fast drying (oven or IR lamps) of the filler applied in too thick layers. - Inefficient filling technique and putty sanding (leaving hollows)
After the complete drying through of the film: - Sand the paint or filler completely to remove the pinholes; apply a suitable sealer filler, sand accurately and re-apply the final coat.
- Follow the prescriptions of the data sheet, respect the thickness of the layer and allow the correct flash off and drying times. - Apply the putty in subsequent thin layers to avoid trapping air in the mass. - Always check the substrate before applying the top coat and, if necessary, operate as indicated above.
Some spots more or less glossy, generally round, on the finishing coat.
The film surface has been abraded because of: - Unsuitable polishing techniques (speed, pressure) or unsuitable materials (rubbing compound, etc). - The film has not dried through yet.
After through hardening of the film: - Repeat the polishing operations. - If necessary sand slightly and re-paint.
- Use specific polishing techniques and materials depending on the finishing coat. - Let dry perfectly the paint film before polishing it.
Bubbles (closed or partially opened) trapped during the application of the paint, being unable to escape because of quick film set up.
Air or solvent vapours trapped in the film, due to: - Too high viscosity. Use of cheap thinners. - Too fast a thinner (especially in summer). - Inappropriate use of fast hardeners. - Too high film thickness or too short flash-off time between coats. - Too high ambient temperature, too near a heating source, too short flash-off time. - The painted car was exposed directly out in the sun immediately after the application of the final coat.- Incorrect drying time before baking (for water-borne clearcoats)
After drying through of the film. - Sand to obtain a smooth surface and re-spray.
- Always follow the data-sheet prescriptions before applying undercoats or finishing coats. - Use the suggested thinners and hardeners depending on the room temperature. - Ensure spray viscosity is correct. - Observe the flash-off times between the coats and the dry time after the final coat. - Control the oven temperature and/or the distance of the IR lamps. - Check at regular intervals the oven temperature control gear. - For waterborne products follow flash-off times before baking.
The film shows more small holes.
Incorrect application of the filler-sealer due to: - Filler application at too high viscosity or use of inappropriate thinner. - Application in layers, which are too thick. - Use of too fast hardeners especially in summer. - Filler drying in the direct sunlight.
After through drying of the film: - Sand thoroughly and re-spray the filler-sealer.
- Observe the prescriptions of the data sheet: apply the fillersealer in the suggested film thickness, respect the flash off time between the coats and let dry correctly. - Check the spray viscosity before applying. - Use the suggested hardeners and thinners, depending on the ambient temperature. - Allow to dry inside the body shop or in areas that do not allow a direct contact with sun rays.
Wrinkling is present in the finishing coat.
The original film was attacked by solvents: - The original coatings were thermoplastic or powder-coats (normally used by car manufacturers). - The original coating (solvent or water-based) had not dried enough
Sand thoroughly, apply a suitable primer (water or epoxy) and re-paint.
Always check the original paint film and choose the suitable paint system
The paint system has been forced up because of rust present on the steel substrate.
- Attack of the metal surface due to contact with weathering and chemical agents. - Presence of humidity on the metallic surface before applying the anti-corrosive primer
Sand the rusted part carefully until bare metal, sand the steel sheet by removing all rust, clean the metal substrate by means of suitable detergents and then repeat the process starting from the anticorrosive primer.
- Repair the damaged points of the paint film as soon as possible. - Clean accurately the metallic surface, dry it with clean cloths, and apply a suitable anti-corrosive primer not later than 30 mins.
Paint drops generally on vertical surfaces.
- Use of unsuitable hardeners/thinners. - Incorrect viscosity. - Heavy application of product. - Incorrect flash-off between coats. - Incorrect air gap. - Incorrect spray fan
Allow the film to dry through, then remove sagging. According to the sagging it will be sufficient to polish or it will be needed to repaint.
the temperature and the relative humidity. - Ensure that the spray equipments are perfectly clean and well working.
Fine scratches can be seen in the top coat.
- The sanding/grit paper was too coarse for the product subsequently applied. - Final sanding with too fine grit paper after previously sanding with coarse grit paper (e.g P180 then P360). - The primer or filler was not sufficiently through hardened for sanding. - Insufficient film thickness
- After it has thorough hardened, sand the top coat smooth with fine sand paper and polish. - If the surface shows serious marks sand thoroughly and reapply the topcoat and the sealer if necessary.
- Consult the data sheet for the substrates (putty and filler) and choose the correct sanding grade. - Using different grades of sand paper follow the prescriptions of the data sheet and of the producer of abrasive papers. - Always let dry through the substrate before sanding (see data sheet). - Apply the top coat in correct film thickness.
Paint particles settled on the car parts not to be painted
The small paint particles settle on the wet film due to: - Inadequate masking of the substrate. - Insufficient ventilation in the spray booth. - Poor spray gun techniques (e.g. spray pressure too high).
In most cases, polishing is sufficient.
- Mask accurately the surface to be protected, especially on the edges. - Follow the application techniques as indicated in the data-sheet. - Check the air flow in the spray booth.
Deep paint film damage due to external agents.
Impacting of the bodywork by stones, pebbles etc.
Sand the damaged zone, apply putty if necessary and then repaint.
Being this phenomenon independent of the human behaviour, only a special attention is required when you meet critical situations of soil, not asphalted roads, little cleaned environments, etc.
The final colour displays streaks in slightly different colours.
Unsuitable application technique due to: - Incorrect adjustment of the spray gun: unsuitable or unclean air cap. - Irregular and/or not constant air pressure. - Too low spray viscosity. - Too wet spraying
After through hardening of the film: - Sand and re-coat.
Choose the spray gun and the relevant nozzle following the prescriptions of the data sheet and of the gun manufacturer. - Check the regular yield of the compressed air. - Always check the spray viscosity of the paint. - Check the quantity and the film thickness of the applied paint.
Marks of evaporated water droplets can be seen on the painted surface.
Traces of water under the surface, due to: - Residual water in case of wet sanding. - Water in the compressed air line. - Contact of the paint surface with rain or with sprinklings of water. - Water not evaporated from the water-borne basecoat and/or filler
After drying through of the film: - Sand the surface and polish it. - In case of deep defects, sand thoroughly and repaint.
- Clean always the surface thoroughly (compressed air and silicon remover degreaser). - Control the compressed air supply to eliminate any trace of water. - Respect correct drying times recommended on the technical data sheet according to temperature and relative humidity.
The edge of evaporated water droplets can be seen on the paint film.
When water drops on the paint surface and evaporates (especially on horizontal surfaces) the outline of the drops may still be seen. This happens when the painted surface has been exposed to rain or water drops just after painting.
Let dry through the film, then: - Sand and polish. - If repeated polishing are not effective, sand the affected area and re-spray.
- Protect the car immediately after the painting and avoid contact with water before it is fully hardened.
The paint surface acquires a finely waved appearance.
- Paint applied to a solvent sensitive and/or only partially dry substrate, without previous application of a suitable sealer. - Use of too aggressive or inappropriate thinner. - Use of unsuitable sealers for the substrate - In case of two-coat finishes, partial removal of the clearcoat by sanding, without correct sealing. - Too high film thickness.
After trough drying of the film: - For a slightly wrinkled surface sand with fine sand paper and re-spray. If the surface shows serious signs of wrinkling, remove thoroughly the paint and apply once more.
- Ensure that the substrate is not sensitive to the solvents and has through hardened. If the case seal completely with a suitable sealer (f.i. water thinnable sealer). - To sensitive substrates it is possible to apply a two components sealer in very thin coats, allowing long flash off times between the coats. - Use only the prescribed hardeners and thinners.