Helpful Guide About Paint Problems

paint problems

 Here is a list of popular paint problems

CRATERS OR SILICONE

 

Small circular, crater-like openings that appear during or shortly after the spray application also known as fish eyes.

Caused by contamination in the airline between the compressor and the spray gun with oil, wax, silicone, grease, etc…

The air intake on the compressor may be sucking in contaminated air.

Paint Problems

Craters or silicones

CRATERS OR SILICONES

Cause

  • Poor cleaning of surfaces.
  • Environmental contamination, mainly by silicones, wax.
  • Water or oil present in the compressed air.
  • Dirty spray guns or equipment.
  • The use of Cheap thinners like Gun-wash or some standard thinners.
  • If the paint is 2K the hardener may be out of date or full of moisture.

Craters or silicones

Solution

  • Thoroughly clean the substrate using the correct degreaser and clean cloths.
  • Change cloths frequently.
  • As a last resort Use anti-silicone additives.
  • Use water filters on your airline some have automatic drain valves.
  • Regularly drain your compressor.
  • Make sure you use the correct thinner and hardener, and that they are in date .
  • Properly clean the spray equipment use a gun washer or strip the gun and clean it.

 

  • APPLICATION PROBLEMS

ORANGE PEEL OR UNEVENESS

Surface showing an uneveness texture due to lack of streching or levelling, that resembles the skin of an orange.

Paint Problems

Orange peel or uneveness

ORANGE PEEL OR UNEVENESS

Cause

  • Too high viscosity of application.
  • Incorrect adjustment of the spray gun, excessive flow rate of the paint and low atomization pressure.
  • Solvents evaporating too quickly.
  • Base layers insufficiently dry.
  • Too much product used when spraying or incorrect position when applying the paint, ie too close.
  • Insufficient preparation or sanding of the previous coats.

Orange peel or uneveness

Solution

  • Reduce the viscosity and increase the dilution rate in other words add more thinners use a measuring cup .
  • Properly adjust and regulate the spray equipment (pressure, flow and geometry of spray pattern) you should spray at 2 bar (29psi)

At the gun not the wall you loose air pressure every meter of airline hose, also use PCL Hi-Flow couplings.

  • Use fast or slow  solvents according to the temperature and the size of the object you are painting, warm conditions and large areas youse slow thinner, small panels and cold conditions use fast thinner, same rules for 2k Hardener.
  • Leave the previous coats to dry properly if you can leave a thumb print in the previous coat don’t paint it till it dries out hard.
  • Adjust the ratio between the flow rate (paint valve on the gun ) and speed of the application, with the correct distance between spray-gun and object you are painting 6inches (20cm).
  • Prepare and sand the previous layers properly.

 

 

 

CRACKING

Partial or total cracking of the painted surface during the application or when drying or dry.

Cracking

  • Incorrect preparation of the paint, wrong type of thinner or hardener.
  • Previous layers that are not dry enough or painting over non compatible paints example, Cellulose over Synthetic.
  • Excessive film thickness layers, too many heavy coats, painting horizontal panels and spraying to heavy coats.
  • painting  objects that are too flexible.

Paint Problems

Cause

cracking_2

Solution

      • Prepare or mix the paint, according to the specification on the  data sheet.
      • Allow the necessary drying times check with the technical data sheet for correct recoat times
      • Apply the correct thickness recommended in the data sheet.
      • Drying times are affected by temperature and humidity the colder and wetter it is the longer the drying times.

 

 

 

PINHOLES OR SOLVENT BUBBLES

Small surface spots produced by the breaking through and deformation of the paint surface. This is caused by the evaporation of the solvent trapped after the outside layer of paint has dried.

 

Pinholes or solvent bubbles

 

PINHOLES OR SOLVENT BUBBLES

Cause

  • Solvents evaporating too quickly.
  • High ambient temperature.
  • Coat application too heavy.

Pinholes or solvent bubbles

Solution

  • Use a slower thinner, only use fast thinners and hardeners in dry cold conditions.
  • Apply lighter coats of paint with longer  flash off times between coats which will allow the evaporation of the solvents between coats.
  • If spraying in a low bake oven reduce the spraying temperature and allow flash off times before going to the bake cycle

 

 

BLISTERS OR AIR BUBBLES

Small blisters caused by the deformation of the painted surface. This is due to trapped moist air escaping after the outside layer of paint has dried.

PINHOLES OR SOLVENT BUBBLES

Blisters or air bubbles

BLISTERS OR AIR BUBBLES

Cause

  • Paint shaken too much before application.
  • Water or condensation on the surface to be painted due to temperature changes.
  • Water in the compressed air.
  • Incorrect regulation of the spray equipment

 

 

Blisters or air bubbles

Solution

  • Leave the paint to rest for the specified period of time after shaking and before application.
  • Make sure the temperature of the surface to be painted is the same as the ambient area to avoid condensation.
  • Use air filters and dryers, and drain the air compressor equipment regularly.
  • Adjust and regulate the application equipment and use paint defoamer if using airless or air mix spray systems .

 

 

SINKAGE

Defect caused when the repaired area, normally with polyester putty, becomes visible within hours, days or weeks after the repair is completed.

Sinkage

SINKAGE

Cause

  • Incorrect preparation and use of the polyester putty.
  • Poor coverage of the repaired area due to incorrectly adjusted spray equipment or poor preparation of substrate.
  • Poor preparation of the patch edges or the area to be repaired.

Sinkage

Solution

  • Correctly prepare, mix and apply the polyester putty that is going to be used, according to its data sheet.
  • Adjust the spray equipment following the data sheet of the paint and apply the correct thickness. Follow the correct evaporation and drying time.
  • Prepare, and correctly isolate the defective area.
CRATERS OR SILICONES

BLOOMING

Lack of gloss, dullness caused by the quick evaporation of the thinner.
This lowers the substrate temperature below the dew point, causing moisture in the air to condense in or on the paint film.

Blooming

BLOOMING

 

Cause

  • Too high relative humidity.
  • Inadequate solvents (not moisture repellent) or solvents evaporating too quickly.
  • Lack of air circulation during the drying process at room temperature.
  • Incorrect preparation of the paint or defective ingredients.
  • Too thick layer.

Blooming

Solution

  • Avoid painting, if the humidity is higher than 80% and temperature is lower than the drew point.
  • Only use solvents recommended by the manufacturer choose a slower thinner and hardener.
  • Make sure there is a supply of fresh  non damp air during the drying process when drying at room temperature.
  • Prepare the paint according to the data sheet and use ingredients that are in  date and good condition.
  • Apply the product according to the specification in the data sheet.
SINKAGE

BLEECHING

Migration of pigment caused by the solvent in the new topcoat dissolving soluble dyes or pigments in the original fi nish, allowing them to seep into and discolour the new topcoat. Usually shown as a red or yellow discoloration on the topcoat, normally happens when spot repair with polyester putties.

Bleeching

BLEECHING

 

Cause

  • Too much Peroxide in the preparation of polyester putties. This reacts with the subsequent layers of paint.
  • Migration of pigment from previous layers caused by the solvent of the final layer.

Bleeching

Solution

  • Prepare the mixture of the polyester putty, according to the specification in the data sheet.
  • Use a sealing coat over the putty and allow to dry before applying any more coats.

 

 

SUBSTRATE CORROSION

Corrosion of the substrate caused by humidity. This creates an electrochemical reaction of the metal with the oxygen which produces rust blisters or fading in the painted surface.

Substrate corrosion

SUBSTRATE CORROSION

 

Cause

  • Untreated corrosion or poor cleaning of the substrate.
  • Exposure of the substrate to corrosive environments ie, salt etc.
  • Substrate exposed for too long after cleaning and before re-painting.
  • Poor pre-treatment of the substrate.

Substrate corrosion

Solution

  • Remove all traces of corrosion and make sure the substrate is clean.
  • Avoid leaving the substrate outdoors without protecting it from corrosive atmospheres.
  • Minimise the time that the substrate is unprotected before priming and further treatment.
  • Use the correct pre-treatment, depending on the type and use of substrate.

 

 

PIGMENT SEPARATION

Separation of the pigments causing stains, stretch marks and creating different layers of uneven colour tones within the coat.

Pigment separation

PIGMENT SEPARATION

 

Cause

  • Incorrect solvent used for the type of paint. Excessive dilution or poor mixing of the paint.
  • Coat thickness too heavy.

Pigment separation

Solution

  • Use solvents that are recommended in the data sheet or contact the manufacturer for advice.
  • Dilute, whilst mixing, according to the data sheet.
  • Apply the correct thickness of the product, following the specifi cations in the data sheet.

 

 

SAGGING

Sagging or running of the paint when applied on vertical surfaces.

Sagging

SAGGING

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Cause

  • Too low viscosity due to an excess of solvent.
  • Too thick layer. Specially when brushing.
  • Use of heavy solvents.
  • Low ambient temperature.
  • Incorrectly adjusted spray equipment, eg, low air pressure, flow rate too high or incorrect distance from the surface.
  • Evaporation time between coats too short.

 

Sagging

Solution

  • Reduce the dilution rate of the paint.
  • This will increase the viscosity.
  • Apply several lighter coats.
  • Use lighter solvents.
  • Slightly increase the temperature of the paint. Increase the room temperature.
  • Properly adjust the spray equipment.
  • Increase the air pressure, reduce the flow rate of the product and increase the application distance from the substrate.
  • Allow the correct drying times between layers following the technical data sheet and according to the application temperature.

 

 

CRAZING

Reaction due to incompatibility between to the base coats.
Insuffi cient drying or hardening of the previous coats.
Use of incorrect solvent.
Topcoat applied in too heavy or wet coats.

Crazing

CRAZING

 

Cause

  • Reaction due to incompatibility between to the base coats.
  • Insufficient drying or hardening of the previous coats.
  • Use of incorrect solvent.
  • Topcoat applied in too heavy or wet coats.

Crazing

Solution

  • Only use base coats or undercoats that are compatible with the fi nishing coats.
  • Allow undercoats to thoroughly dry/cure before topcoating following the technical data sheet.
  • Only use solvents recommended by the manufacturer and according to the conditions of the application.
  • Follow the coat thickness and the fl ash time recommended in the technical data sheet.

 

 

OVERSPRAY

Paint particles that reach dry the painted surface resembling a fi ne dust fi nish.

Overspray

OVERSPRAY

 

Cause

  • Too fast drying solvents. High ambient temperature.
  • High application pressure.
  • Low fl owrate of paint using too much air.
  • Distance too far from the spray gun to the substrate.
  • High viscosity of application.
  • Inadequate adjustment of spray equipment.

 

Overspray

Solution

  • Add a slower evaporating solvent.
  • Avoid painting when the temperature is high.
  • Reduce the pressure of the spray gun.
  • Increase the fl owrate of the paint.
  • Reduce the distance from the spray gun to the substrate.
  • Adjust the viscosity of the paint when spraying.
  • Correctly adjust the spray equipment that is going to be used.

 

 

EXTENDED DRYING TIMES

The paint fi lm is soft to the touch, and will fingerprint or water spot within hours/days after application.

Extended drying times

EXTENDED DRYING TIMES

 

Cause

  • Low ambient temperature or high relative humidity.
  • Use of solvents which are slow to evaporate.
  • Too heavy coats.
  • Paint old and out of date.
  • Incorrect mixing ratio in the hardener (2K products).

 

Extended drying times

Solution

  • Dehumidify and heat the premises.
  • Use the correct solvent.
  • Control the thickness of the paint.
  • Add the recommended hardeners or accelerators by the manufacturer.
  • Follow the indicated mixing ratios in the Technical Data Sheet.

 

 

LACK OF ADHESION

A loss of adhesion or separation of the paint fi lm from the substrate.

Lack of adhesion

LACK OF ADHESION

Cause

  • Incorrect preparation of the surface leaving grease or moisture.
  • Previous layers in bad conditions.
  • Inapropiate sanding.
  • Wrong choice in the paint system.

 

Lack of adhesion

Solution

  • Clean and prepare the surface properly.
  • Remove loose and flaking paint. Degrease the surface properly.
  • Sand the surface properly.
  • Get advice from the manufacturer about paint system to use.
EXTENDED DRYING TIMES

WATER MARKS

Circles with raised edges or whitish spots resembling the various shapes of water droplets appear on the surface of the paint fi lm.
Caused by allowing water to come into contact with a fi nish that is not thoroughly dried/cured.

Water marks

WATER MARKS

Cause

  • Exposure of the painted surface to a humid atmosphere.
  • Water splashes or drops of rain on the painted surface.

 

Water marks

Solution

  • Do not allow water to come into contact with newly painted fi nish.
  • If a new finish does get wet, dry immediately with a soft cloth.
LACK OF ADHESION

SANDING MARKS

Visible lines or marks in the paint fi lm that follow the direction of the sanding process.

Sanding marks

SANDING MARKS

Cause

  • Insufficient dry/cure of undercoats before sanding and top coating.
  • Incorrect selection of the sanding orbit.
  • To coarse a choice of  sandpaper grit.
  • Paint layer too thin to cover and fill the sanding marks.
  • Inadequate preparation of previous layers of paint.

 

Sanding marks

Solution

  • Follow the drying times as stated in the data sheet before sanding.
  • Depending on the coat that needs sanding, choose the correct orbit for the sander. Use small orbits for fi nishing coats.
  • Choose the correct grit sandpaper, taking into account the thickness of the paint that needs sanding.
  • Sand the surface with the aim of applying only enough paint to cover or fi ll the marks.
WATER MARKS

DUST AND DIRT

Foreign particles embedded in paint film.

Dust and dirt

DUST AND DIRT

Cause

  • Inadequate cleaning of the surface to be painted.
  • Dirty spraying environment.
  • Paint contaminated with dirt.
  • Compressed air contaminated or dirty spray equipment.
  • Dust in the air.

 

Dust and dirt

Solution

  • Clean the surface to be painted removing all dust and dirt.
  • Maintain a clean working area. Keep correct maintenance of the booths and change fi lters regularly.
  • Use strainers or filter the paint.
  • Maintain the compressed air installation and application equipment. Regularly
  • clean filters, hoses, separators, etc.
  • Keep the area clean, use antistatic clothes, etc.
SANDING MARKS

OPACITY

The original finish or undercoat is visible through the topcoat.

Opacity

OPACITY

 

Cause

  • Insufficient thickness or number of colour coats applied.
  • Substrate not uniform in colour.
  • Colour over-thinned/reduced.
  • Use of pigments with poor hiding power lead free (pb) .

 

Opacity

Solution

  • Apply the necessary thickness to cover the lower layers.
  • Use a sealer or ground coat to provide a uniform colour before top coating.
  • Thin/reduce according to product label information TDS sheet.
  • Use an undercoat that is similar in colour to the topcoat pick a shade of grey.
  • Use a 3M colour check light to check opacity (Coverage)

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