Common Spraying Defects: Causes, Prevention, and Repair Solutions

Introduction

Spraying is one of the most widely used surface finishing techniques across industries—from automotive and furniture manufacturing to construction and home renovation. While spraying delivers a smooth, professional-looking finish, even experienced operators encounter defects from time to time.

Understanding the most common spraying defects, their root causes, and practical solutions is critical for minimizing waste, reducing rework costs, and maintaining product quality.

In this article, we'll walk you through the top 8 spraying defects, why they happen, and exactly how to fix them.

1. Runs / Sags (Paint Drips)

What it looks like: Vertical streaks or curtain-like drips on the surface.

Causes:

• Applying too heavy a coat

• Moving the spray gun too slowly

• Spraying too close to the surface

• Paint viscosity too low (over-thinned)

Prevention:

• Apply multiple thin coats rather than one heavy coat

• Keep the spray gun at the correct distance (usually 6–10 inches)

• Maintain proper gun speed and overlap (50%)

• Check and adjust paint viscosity as per the technical data sheet

Repair:

• If the paint is still wet: wipe off immediately with a clean cloth and re-spray

• If cured: sand down the drips with fine-grit sandpaper (e.g., P400–P800), then polish or recoat

2. Orange Peel (Rough, Textured Surface)

What it looks like: A bumpy, uneven surface that resembles the skin of an orange.

Causes:

• Paint viscosity too high (not enough thinner)

• Gun pressure too low (poor atomization)

• Spray gun held too far from the surface

• Incorrect thinner or hardener ratio

Prevention:

• Thin the paint to the correct viscosity (use a viscosity cup)

• Increase air pressure to improve atomization

• Keep the gun at the recommended distance

• Use the recommended thinner and hardener

Repair:

• For mild orange peel: wet-sand with P800–P1200 sandpaper, then machine polish

• For severe cases: sand back completely and re-spray

3. Fish Eyes (Cratering / Silicone Contamination)

What it looks like: Small, round depressions (craters) in the paint film.

Causes:

• Contamination on the surface (silicone, oil, wax, grease)

• Contaminated compressed air (oil/water in the air line)

• Poor surface cleaning or degreasing

• Use of silicone-based polishes or release agents near the booth

Prevention:

• Thoroughly clean and degrease the surface before spraying

• Use separate, clean rags for each cleaning step

• Install oil/water separators on your air compressor

• Never use silicone-based products in or near the spray booth

Repair:

• Light sanding and re-spraying is usually required

• In stubborn cases, you may need to apply a filler/primer first, then sand and re-spray

4. Pinholes / Bubbles (Micro-Sized Holes)

What it looks like: Tiny holes or bubbles in the paint film after drying.

Causes:

• Trapped air or moisture under the paint layer

• Painting over porous surfaces without sealing

• Applying paint too thickly, trapping solvents

• Spraying in high-humidity conditions

Prevention:

• Use a primer/sealer on porous substrates

• Apply thin, even coats; allow flash-off time between coats

• Avoid spraying in very humid or rainy weather

• Ensure the substrate is completely dry

Repair:

• Sand the affected area down to the primer, re-prime if necessary, and re-spray

• For minor pinholes, apply spot putty, sand smooth, and re-spray

5. Blushing / Clouding (White Haze)

What it looks like: A milky, whitish, or cloudy appearance, especially on clear coats.

Causes:

• Spraying in high humidity or cold conditions

• Moisture trapped in the paint film

• Evaporation of solvents too quickly (cooling the surface)

Prevention:

• Use a slower-evaporating thinner (retarder) in humid or cold weather

• Avoid spraying when relative humidity exceeds 80%

• Warm up the workshop or substrate before spraying

Repair:

• For mild blushing: re-coat with a slow thinner or apply a heat lamp to drive out moisture

• For severe blushing: sand and re-spray

6. Dry Spray / Overspray (Rough, Powdery Finish)

What it looks like: A rough, dry, matte, or powdery texture on the surface.

Causes:

• Spray gun held too far from the surface

• Paint drying before it reaches the surface

• Low air pressure or insufficient paint flow

• Spraying in warm, drafty conditions

Prevention:

• Keep the gun at the correct distance (6–10 inches)

• Adjust air pressure and fluid flow properly

• Avoid spraying in windy or drafty conditions

• Overlap strokes by 50%

Repair:

• Sand lightly with P800–P1200 and re-spray

• For minor overspray: machine polish can sometimes remove it

7. Cracking / Crazing (Fine Lines or Cracks)

What it looks like: Fine hairline cracks or wider cracking in the paint film.

Causes:

• Applying paint too thickly in one coat

• Insufficient flash-off time between coats

• Using incompatible primers or topcoats

• Excessive temperature changes (thermal shock)

Prevention:

• Follow the recommended dry film thickness

• Allow adequate flash-off time between coats

• Use compatible products from the same system

• Control workshop temperature and avoid extreme shifts

Repair:

• Sand back completely to the substrate

• Re-prime, sand, and re-spray

8. Poor Adhesion / Peeling (Paint Lifting)

What it looks like: Paint lifting, flaking, or peeling off the substrate.

Causes:

• Inadequate surface preparation (not sanding or cleaning)

• Grease, oil, or rust left on the surface

• Incompatible primer and topcoat

• Sanding too smooth (no “tooth” for mechanical adhesion)

Prevention:

• Always sand the surface properly (P180–P320 for primers, P400–P600 for topcoats)

• Degrease thoroughly before applying any coating

• Use a compatible primer and topcoat system

• Apply an etching primer on bare metal

Repair:

• Strip all loose paint off the surface

• Sand down to bare substrate

• Re-apply primer, sand, and re-spray