The halo effect in coatings is one of the most common and frustrating defects. It appears as bright rings or uneven patches that make surfaces inconsistent. Fortunately, this problem can be avoided by following proper procedures and selecting suitable raw materials. Discover below the essential measures that help control and minimize the halo effect effectively.
Ways to Prevent the Halo Effect in Coatings
Careful surface preparation
A solid substrate is the foundation of a flawless finish. Before application, dust, oil, and moisture must be completely removed. For metal, rust should be treated and a protective primer applied. For wood, sanding is required to achieve a smooth surface and better adhesion.
It is also important to ensure the primer and topcoat are compatible. When coating layers work together, the film becomes stable and the risk of uneven color decreases. Good preparation removes most chances of the halo effect from the start.
Controlling solvents and viscosity
Solvents determine evaporation speed and coating smoothness. If the wrong solvent is used, halos may easily form. It is essential to select one with an evaporation rate suitable for the application conditions.
Paint should also be mixed according to the manufacturer’s recommendation. Proper viscosity allows the film to level naturally and prevents blotchy marks. With both solvent and viscosity under control, the coating remains uniform and stable.
Using correct spraying techniques
Spray technique directly affects surface uniformity. The applicator should keep a stable spray gun distance, usually 20–25 cm. Movements must be smooth and parallel, avoiding long pauses in one spot.
Thin and even coats are recommended, rather than applying one thick layer. In some cases, the “wet-on-wet” method—spraying the next coat before the previous one is fully dry—creates a seamless film and significantly reduces the halo effect.
Controlling application environment
The application environment is crucial but often overlooked. Strong wind disperses spray unevenly, while high temperatures cause solvents to evaporate too quickly and leave blotchy areas.
Humidity also matters. Low humidity prevents smooth leveling, while high humidity can make the film cloudy and less glossy. Therefore, application should be done in facilities with ventilation, dust control, and stable temperature and humidity. A controlled environment greatly limits the halo effect.
Raw materials and additives that reduce halos
Beyond application techniques, the use of suitable raw materials and additives helps reduce halo problems. Wetting and leveling agents promote even pigment distribution and improve consistency. Silicone- and acrylic-based additives can enhance flow and reduce blotches.
In waterborne systems, Bayhydrol A145 (Covestro) is well regarded for its stable pigment dispersion. Combined with proper additives and correct pH, it lowers the risk of the halo effect noticeably.
High-quality TiO₂ pigments also play a vital role. With strong opacity and excellent light reflection, TiO₂ allows light colors to cover dark bases evenly, reducing contrast and minimizing bright rings.
Explore TiO₂ pigment products officially distributed by Vichem:
How to fix and correct the halo effect
When the halo effect has already developed, prompt correction is necessary. For small areas, light sanding followed by a thin and even repaint can be effective.
For large areas, the best solution is to sand away the defective layer and reapply starting from the primer. In many cases, adding suitable additives or adjusting solvent blends before respraying improves uniformity of the new coat.
To avoid recurrence, applicators should review the entire process: surface preparation, environmental conditions, and spraying technique. This ensures the new coating remains stable and visually appealing.
VICHEM – ĐẠI LÝ PHÂN PHỐI PHỤ GIA HOÁ CHẤT ĐẠT CHUẨN CHÍNH HÃNG TẠI VIỆT NAM
Vichem is an officially authorized distributor of chemical additives in Vietnam, fully compliant with legal regulations. We not only supply certified products but also provide international-standard after-sales services, including:
- Technical consulting: Assisting customers in selecting the right products.
- Color matching tests: Performed by Vichem experts to ensure design standards are met.
- Application support: Guiding customers during integration into production lines for optimal results.
For more information, please contact us via the following channels:
📞 Hotline: 08 1790 1790
📧 Email: contact@vichem.vn
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🌐 Website: www.vichem.vn
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