Useful Industry Definitions: Common Paint Defects
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Understanding common paint and coating defects is essential for improving finish quality and identifying application, material, surface-preparation, or environmental problems before they become costly.
The following definitions explain four defects frequently encountered in professional painting and industrial finishing operations.
1. Bleeding
Definition:
Bleeding is a color distortion that occurs when soluble dyes, stains, or pigments from an underlying material or coating migrate into the new topcoat. The contamination may appear as discoloration, staining, or an unwanted color change.
Common causes:
Solvents in the new coating may reactivate soluble colorants in the underlying finish or substrate. Bleeding can also occur when incompatible coatings are applied over certain stains, dyes, asphaltic materials, wood extractives, or previously contaminated surfaces.
2. Blistering
Definition:
Blistering is the formation of raised bubbles or dome-shaped areas within or beneath a paint film. The blisters may contain air, moisture, solvent vapor, or liquid.
Common causes:
Blistering may result from trapped moisture or solvent, excessive film thickness, applying coating to a hot or damp surface, poor surface preparation, contamination, inadequate flash time, or loss of adhesion between coating layers.
3. Blooming
Definition:
Blooming is the development of a dull, hazy, cloudy, or sometimes powder-like condition on the surface of a coating. It can reduce gloss and alter the intended appearance of the finish.
Common causes:
Blooming can result from moisture, low curing temperatures, airborne contamination, incompatible coating components, incomplete curing, or the migration of certain coating ingredients to the surface.
4. Blushing
Definition:
Blushing is the formation of a whitish, milky, or cloudy appearance within a coating film. It is most commonly associated with fast-drying solvent-based finishes such as lacquer.
Common causes:
When solvent evaporates rapidly in humid conditions, the coating surface can cool enough to cause moisture from the surrounding air to condense in the wet film. Incorrect thinner selection, excessive atomizing air, low material temperature, or poor environmental control can increase the risk.
A Practical Troubleshooting Reminder
Correctly identifying a defect is only the first step. Similar-looking problems can have different causes. Before changing the spray equipment, evaluate the
substrate, surface preparation, coating compatibility, material temperature, viscosity, film thickness, flash time, air quality, humidity, and curing conditions.
Professional tip: Record the coating, reducer, mixing ratio, spray settings, temperature, humidity, and application results. A dependable spray log makes recurring finish defects much easier to diagnose.
Need Help Troubleshooting a Finish Problem?
Contact
Azimuth Spray Systems for help evaluating your spray equipment, application settings, compressed-air requirements, and finishing process.
Providing Direction — Improving Performance!
Azimuth Spray Systems, LLC
Phone: 817-490-1777
Email:
[email protected]
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