Pinholing (Boiling Defect)

Problem Description:

Pinholing refers to the appearance of small, round holes on solvent-based paint surfaces, typically caused by rapid solvent evaporation.

Possible Causes:

• Rapid Solvent Evaporation: Low humidity and high temperatures accelerate solvent evaporation, causing pinholing.
• High Application Temperature: Applying paint in a hot environment causes solvents to evaporate too quickly, leading to boiling defects.
• Insufficient Drying Time: Applying upper coats before the underlying layers have dried adequately traps solvent, preventing proper evaporation.
• Incorrect Paint Formulation: Excessive solvent or incompatible solvents in the formulation accelerate evaporation and cause defects.

Solutions and Precautions:

• Thinner Selection: Avoid fast-evaporating thinners; prefer medium to slow evaporating thinners such as polyurethane thinners.
• Allow Adequate Drying Time: Ensure sufficient drying time between coats.
• Application Technique: Apply paint in thin layers to allow uniform drying.
• Ensure Proper Airflow: Maintain appropriate air circulation in the painting area.

Pinholing can be prevented by selecting proper materials and maintaining controlled application conditions.