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:
- Not reading the manufacturer’s technical data sheet (TDS)
- Misjudging paint drying times
- Incorrect gun setup
- Air pressure too low
- Air pressure too high
- Dirty equipment/blocked filters
- Poor surface preparation
PART TWO: Poor adhesion
- Edge mapping/feather-edge lifting
- Peeling
- Wrinkling/lifting (urethanes and enamels)
- Chips
PART THREE: Poor finish - surface texture
- Air trapping
- Cracking/webbing
- Crows feet
- Dimpling
- Grainy finish
- Fisheyes
- Grit/Debris
- Pimpling
- Orange peeling
- Sags
- Softness
- Static
PART FOUR: Poor finish - colour
- Blushing
- Bleeding
- Discolouration
- Dulling/hazing
- Misting/fogging
- Mottling
- 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
Film thickness
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.
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.
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.
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.
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.
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:
- Fill or sand out cracks in the surface that you’re painting.
- Check the technical data sheet of primers, basecoats and topcoats for:
- The correct film thickness
- Drying and curing times
- Hardener ratios
- 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
If you're having problems with your paint, contact our technical Total Paint Shop Support team for more information.