30 Paint Spraying Problems and Fixes | Ultrimax | UK

 

paint problems

30 Common Paint Spraying Problems and How to Avoid (or Fix) Them

When a paint job goes wrong it’s more than a little frustrating; it’s costly. Refinishing a defective product brings labour and material costs that shrink your profit margins. And in some cases, it can even cost you a client.

 

Over the years, our clients have asked us for advice on all sorts of paint spraying problems. This guide covers the most common issues that we have come across. It will help you to:

  • Identify each problem
  • Understand why it happens
  • Learn how to avoid it
  • Learn how to fix it.

 

  CONTENTS:[1]

 

PART ONE: Painter mistakes that contribute to a poor finish

  1. Not reading the manufacturer’s technical data sheet (TDS)
  2. Misjudging paint drying times
  3. Incorrect gun setup
  4. Air pressure too low
  5. Air pressure too high
  6. Dirty equipment/blocked filters
  7. Poor surface preparation

PART TWO: Poor adhesion

  1. Edge mapping/feather-edge lifting
  2. Peeling
  3. Wrinkling/lifting (urethanes and enamels)
  4. Chips

PART THREE: Poor finish - surface texture

  1. Air trapping
  2. Cracking/webbing
  3. Crows feet
  4. Dimpling
  5. Grainy finish
  6. Fisheyes
  7. Grit/Debris
  8. Pimpling
  9. Orange peeling
  10. Sags
  11. Softness
  12. Static

PART FOUR: Poor finish - colour

  1. Blushing
  2. Bleeding
  3. Discolouration
  4. Dulling/hazing
  5. Misting/fogging
  6. Mottling
  7. Sand scratches

 

PART ONE: Painter mistakes that contribute to a poor finish

1. Not reading the manufacturer’s technical data sheet

This little spraying sin is responsible for so many bad paint jobs, especially amongst newbie sprayers. The manufacturer’s technical data sheet contains all the information you need to get the finish right, so do yourself a favour and familiarise yourself with it in advance of using a product. The technical data sheet, details the correct hardener and thinners to be used if applicable as well as spray gun set up, film thickness, drying and re-coat times.

2. Misjudging paint drying times

If you don’t leave enough time between coats, your paint finish will suffer. But as any seasoned painter knows, there are many factors that can cause you to misjudge drying times and go in with the second coat too soon.

Atmospheric conditions

Cold and humid environments will slow your drying times considerably and can negatively affect your finish in several ways. You can mitigate these issues by:

  • Investing in suitable heaters and dehumidifiers for your paint shop
  • Reading the Technical Data Sheet for guidance on minimum temperatures and humidity levels
  • Planning - consider how weather conditions might affect drying times

 

Buy paintshop heaters and dehumidifiers online

paint problems with IR Heaters

Iwata Infra Red Heater

Film thickness too thick

This one isn’t rocket science. If you apply a thicker film than the manufacturer states, it will take longer to dry. So always follow the data sheet guidance on film thickness and get yourself a decent film thickness gauge.

 

Learn about film thickness

.

Buy film thickness gauges online

wet film thickness gauge

Wet Film Thickness Gauges

 

Incorrect solvent/too much solvent

Too much solvent or using too fast a solvent will accelerate drying time, resulting in a poor ‘sandpaper’ finish. Read the data sheet and this won’t happen…

 

Impatience

Whether you’re a DIYer who is eager to see the end finish or you’re a paint shop sprayer who is behind on a production run, impatience is your enemy. If a product’s data sheet states a 4-hour drying time, 2 hours just won’t cut it.

Guessing drying times

It can be tempting to guess drying times based on similar products that you have used in the past. Don’t do it! If you get it wrong it will lead to one of two far from ideal scenarios:

  • You will topcoat too soon and negatively impact the final finish.
  • You will set up your work station, have a quick read of the data sheet and realise that you need to allow 2 hours drying time and not the 15 minutes that you’d allocated. Oops.

Both scenarios will ultimately slow down production and put you behind schedule.

3. Incorrect gun setup

Pimples, blisters, fizz holes, runs and overspray are just a few of the issues that can result from incorrect gun setup or using the wrong size spray tip. Check the product data sheet ahead of setup to avoid running into problems.

4. Air pressure too low

You know your pressure is too low for the job on an airless paint sprayer when your pressure is around 100 bar and you experience the following:

  • The spray pattern becomes patchy
  • More material is being applied towards the outer edges than the centre.
  • Product distribution is uneven in the central area.

However, if you’re at 200 bar and the spray pattern is spotty, you’ve probably got a worn out nozzle.

 

Buy spray gun tips online

airless spray tips

Buy Airless Spray tips online

 

5. Air pressure too high

It’s a common misconception amongst painters that upping the pressure will speed up the job and achieve a more even finish. In reality, using more pressure than necessary results in:

  • Overspray
  • Excessive product consumption
  • Increased wear and tear to gun parts and tips

The key is to work with the lowest pressure needed to achieve an optimal finish. Start with a low pressure of around 100 bar and gradually increase it until you achieve a uniform distribution of material.

6. Dirty equipment/blocked filters

Debris in your finish is never a good look. But that’s exactly what you’ll get if you don’t keep your kit clean. A dirty gun, blocked gun filters or clogged extraction filters will always produce a sub-standard end product.

 

Buy spray gun filters and cleaning products online

spray booth filters

 

PART TWO: Spray painting problems - poor adhesion

8. Edge mapping/feather-edge lifting

IDENTIFICATION: Patches of finish that have lifted in ‘feathers’ around the edge of an area that you have repaired.

Causes

This defect happens when solvents in the topcoat penetrate through areas of the undercoat.

How to avoid it

You can prevent this problem from occurring by using a suitable primer to create a good barrier layer and stable base for the paint repair.

How to fix it

Depending on the extent of the delamination, you will either need to remove the problem area fully and start again or sand it back to a stable surface.

9. Peeling

IDENTIFICATION: Areas of topcoat have peeled.

Causes

The film hasn’t adhered to the surface beneath it due to insufficient prep and/or using the wrong primer.

How to avoid it

Proper surface preparation - thoroughly sand and clean the substrate and then use a suitable primer.

How to fix it

Sand back, start again and give yourself a talking to about skimping on the prep!

10. Wrinkling or lifting (urethanes and enamels)

IDENTIFICATION: Wrinkling either when applying a new finish or when the finish is drying.

Causes

This happens when solvents in your new finish attack the old finish, causing it to become unstable and lift. .

How to avoid it

This is a timing issue. Make sure that you recoat within the manufacturer’s stated recoat window so that a mechanical bond can form between layers. If you miss this window, wait for the full curing time stated on the data sheet. The coating will then be hard enough to sand, recoat and achieve a mechanical bond.

How to fix it

Sand back and recoat within the required timeframes.

11. Chips

IDENTIFICATION: Small areas of finish that have lost adhesion to the substrate. The edges of a chip are clean rather than flaking.

Causes

  • Insufficient cleaning and/pr preparation prior to spraying.
  • Materials not properly mixed.
  • Incorrect metal treatment.
  • No use of/wrong use of sealer.

How to avoid

  • Degrease the substrate and properly prepare it for painting.
  • Use the correct metal etcher primer.
  • Mix all products thoroughly.
  • Use the correct paint system - follow the manufacturer’s Technical Data Sheets

How to fix

Sand back, removing finish from an area that is slightly bigger than the chip, prime and refinish according to the manufacturer’s technical data sheet.

 

Buy degreasers and metal etch primers online

primer paint

 

PART THREE: Spray painting problems - defective finish texture

12. Air trapping

IDENTIFICATION: Tiny craters in your finish.

Causes

Tiny air bubbles have risen to the surface and popped, leaving craters behind.

How to avoid it

Make sure your spray gun is adjusted to the correct air pressure setting for the material that you’re spraying and keep the nozzle a suitable distance from the surface that you’re coating.

How to fix it

Sand the affected area with 1200-grit sandpaper and polish it.

 

Buy sanding pads and sandpaper online

sia sanding discs

 

13. Cracking/Webbing

IDENTIFICATION: Your surface finish develops a crackled or spider web appearance.

Causes

  • Your undercoat or topcoat film is too thick.
  • You haven’t allowed enough time for a primer, basecoat or topcoat layer to dry and cure before adding a coat.
  • You have painted over a cracked surface.
  • You have used too much hardener.
  • You have used two incompatible products and it has caused a chemical reaction.

How to avoid it

Before painting, make sure you take the following steps:

  1. Fill or sand out cracks in the surface that you’re painting.
  2. Check the technical data sheet of primers, basecoats and topcoats for:
    1. The correct film thickness
    2. Drying and curing times
    3. Hardener ratios
    4. The correct paint system to use

How to fix it

Film coat too thick - strip back and refinish using correct film thickness.

Curing - sand back to a flat surface, and recoat after leaving to cure for the correct amount of time.

Cracked surface - strip back to a flat surface or sand back and fill if necessary.

Too much hardener - strip back and refinish using the correct amount of hardener.

Paint reaction - sand back to a bare substrate and start again or sand and apply a barrier paint before refinishing.

14. Crow’s feet

IDENTIFICATION: Cracks in your topcoat.

Causes

  • Applying too thick a film coat
  • Using a blowtorch to speed up drying times
  • Not leaving long enough between coats
  • Using too much hardener or catalyst

To avoid it

Always refer to the technical data sheet for product film thicknesses, drying times and hardener ratios. Never use a blowtorch to dry things out quickly!

To fix it

Strip back to a sound surface and redo the job.

15. Dimpling

IDENTIFICATION: Small pinholes in your paintwork.

Causes

Applying primer too thickly or not allowing it to fully dry before recoating.

How to avoid it

Check the manufacturer’s technical data sheet sheet for film thickness and drying time requirements.

How to fix it

Sand back to the substrate and reapply the primer in thinner layers.

16. Grainy finish

IDENTIFICATION: A grainy-looking finish.

Causes

Spraying from too far away from the substrate. The paint particles atomise and dry before they land.

How to avoid it

Spray on a practice piece to gauge the optimal distance.

How to fix it

Grainy - sand back, test distances on a practice piece and then respray.

Paint runs - don’t wipe or mess with the runs. Let them fully cure, sand them out and reapply base and topcoats.

17. Fisheyes

IDENTIFICATION: Crater-like dimples in your paint’s surface that appear during or after spraying.

Causes

The substrate is contaminated with wax, grease or oil.

How to avoid it

Always clean your substrate with a degreaser at the end of the prep phase before priming or painting.

How to fix it

Sand back to the substrate, degrease and redo the job.

 

Buy degreasing products online

degreaser and panel wipe

 

18. Grit/debris

IDENTIFICATION: Visible foreign particles in your paint/a gritty finish.

Causes

Spraying in a dirty or dusty work environment.

How to avoid it

  • Strain or stir your product properly.
  • Avoid using old tins of primer or paint.
  • Clean the surface before painting it.
  • Paint in a dirt and dust-free environment.
  • Wet the floor of your work areas before spraying and between coats to keep airborne contaminants to a minimum.

How to fix it

Allow the item to cure and then sanding and re-spray.

19. Pimpling

IDENTIFICATION: Swollen areas in the paint’s surface that appear weeks or months after completing the spray job.

Causes

Moisture is trapped under the surface of the paint.

How to avoid it

Pimpling is the result of moisture becoming trapped under the surface of the paint. To avoid this, paint in a dry area and use a dehumidifier if you are working in high humidity.

How to fix it

Sand back and start again.

 

Buy humidity detectors online

humidity detector

 

20. Orange peel

IDENTIFICATION: Your surface finish has an orange peel texture.

Causes

Either the spray gun`s air pressure is too low or the paint has not been thinned sufficiently.

How to avoid it

  • Always thin your product according to the manufacturer’s technical data sheet.
  • Check that your air pressure is right and you’re not spraying too close to the substrate. (Spray the product on a test piece first if you’re not confident about air pressures and spray distances).

How to fix it

Minor cases of orange peel can be corrected by wet sanding with 1200-grit sandpaper and then buffing. More serious cases will have to be sanded back to an even surface and resprayed.

 

Buy 1200-grit sanding pads and sandpaper online

sanding discs

 

21. Sags/paint runs

IDENTIFICATION: Downward runs of paint on vertical surfaces. Sagging can appear in a local area shortly after spraying or over a long run known as a ‘curtain’.

Causes

Most DIYers and junior painters will have experienced this one at some point. They happen when you:

  • Hold the paint gun too close to the substrate
  • Accidently double-coat an area
  • Move too slowly over the surface
  • Thin the paint too much
  • Paint in cold conditions

How to avoid it

  • Practice your spray technique. Hold your gun perpendicular to the surface you’re spraying, keeping around an outstretched arm’s leg away and move the gun in swift, even strokes.
  • Check the product technical data sheet for minimum temperatures before painting.

How to fix it

Let the sags fully cure, then sand out and refinish.

22. Softness

IDENTIFICATION: A finish that remains soft once dry, and is susceptible to fingerprints and water marks for days after spraying.

Causes

Softness is the result of spraying the undercoat or topcoat too heavily or not allowing enough drying time between coats.

How to avoid it

Read the manufacturer’s technical data sheet for film thickness, thinner requirements and drying times.

How to fix it

Remove the offending layers and recoat.

23. Static

IDENTIFICATION: Shadows or dust in your paintwork.

Causes

Static is a common problem when painting plastics. The act of rubbing the panel or “tacking off” creates a static charge that attracts dust in even the cleanest work areas.

How to avoid it

Prepare your surface with an anti-static gun. It will remove dust from surfaces and neutralises the static charge to avoid re-attraction.

How to fix it

Sand back to a smooth surface and refinish.

 

Meet the Iwata bellaria spray gun

 

bellaria iwata spray gun

 

 

Buy the Iwata W400 gun online

iwata w400 spray gun

 

 

PART FOUR: Spray painting problems - finish colour

24. Blushing

IDENTIFICATION: A cloudy look to the surface of your finish.

Causes

Spraying in a humid environment - the “blushing” phenomenon happens when solvents in the paint evaporate and reduce the surface temperature below the dew point, causing moisture to get trapped in the paint layer.

How to avoid it

Use a high-quality reducer that is designed for the atmospheric conditions in which you will be painting.

How to fix it

Strip back, add a suitable retarder to the paint and recoat.

 

Buy reducers online

thinners and retarders

25. Bleeding

IDENTIFICATION: A yellow stain appears in the topcoat above an area of glazing putty or filler.

Causes

This can happen for a few reasons, all of which are to do with the hardener in the filler. In most cases it will be caused by one of the following:

  • Too much or too little hardener in your filler
  • Not mixing the filler properly
  • Priming before the filler has fully cured.

How to avoid it

Use a stain-free filler and a sealer coat before applying the colour.

How to fix it

Start over. Sand back, remove the filler and refinish with stain-free filler and sealer.

 

Buy stain-free fillers online

body fillers

 

26. Discolouration

IDENTIFICATION: Staining in your colour finish.

Causes

Discolouration usually occurs when solvent in the topcoat dissolves soluble pigments in the old finish below.

How to avoid it

If you’re painting over an existing finish that may contain soluble pigments, prep it and seal it before adding the new topcoat.

How to fix it

Allow your discoloured finish to fully cure, then seal it and topcoat again.

 

Buy sealers online

27. Dulling/hazing

IDENTIFICATION: A finish that dulls as it dries.

Causes

Dulling can be a symptom of several types of issue, but the most common cause is using the wrong primer or topcoating the primer/undercoat before it has fully cured.

How to avoid it

Refer to the undercoat manufacturer’s technical data sheet to establish the correct paint system and curing times and stick to them!

How to fix it

In most cases, you will be able to restore shine with a compound and polish. If the dulling is severe, sand back the topcoat and refinish.

 

Buy compounding and polishing equipment and sundries online

compounds and polishes from 3M

28. Misting/Fogging

IDENTIFICATION: Foggy/misty patches in the final finish.

Causes

The substrate or paints have been too cold before you spray.

How to avoid it

Unless the product’s technical data sheet states otherwise, don’t be tempted to spray if your work area is below ambient room temperature. In cold weather, plan ahead and use a suitable heat source to raise the room temperature.

How to fix it

Sand back, prime and refinish.

 

Buy paintshop heaters online

paint shop heater

 

29. Mottling (metallic/transparent finish)

IDENTIFICATION: Streaks in your metallic or transparent finish.

Causes

  • An unbalanced spray pattern (dirty spray gun, incorrect pressure or worn out tip)
  • Wrong spray angle
  • Improperly mixed materials
  • Over-thinning
  • Tilting the gun
  • Clear-coating before your basecoat has cured

How to avoid it

  • Test your gun’s spray pattern before starting the paint job and correct accordingly.
  • Avoid excessive film-build by spraying with a swift and even motion, holding the gun at 90 degrees to the substrate.
  • Allow sufficient flash time between coats (check product TDS).

How to fix it

Refer to the product manufacturer’s TDS for instructions on how to correct streaking. This may involve spraying a “control” coat.

Buy spray tips and control coats online

air assisted airless spray tips

 

30. Sand scratches

IDENTIFICATION: These streaks or lines are sanding marks that appear through the paint film.

Causes

  • The substrate was sanded with an abrasive that was too coarse
  • Wrong sanding technique or sanding machine used
  • Undercoat materials had insufficient drying time
  • Filler and topcoat layers were applied to thinly

How to avoid

  • Check the product’s Technical Data Sheet for correct preparation methods, drying times and film builds.
  • Use a guide coat when sanding.
  • Keep to recommended drying times.
  • Keep to recommended film builds.
  • Place the sanding machine on the substrate before switching it on.
  • When dry-sanding filler coats, keep eccentric strokes below 5 mm.

How to fix

Denib the area and refinish using the recommended paint system.

 

Conclusion

Most paint spraying problems are avoidable when you:

  • Follow best practice
  • Use high-quality products
  • Practice your spraying skills
  • Spray a test piece if necessary
  • Plan ahead
  • Don’t cut corners!

Although there is almost always a fix for a spray job gone wrong, taking measures to get it right first time will save you time, money and a lot of frustration.

 

Need more help?

If you can’t find a fix for the issue you’re experiencing or you need more advice, drop us a line and we’ll get your paint job on track.

 

 

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