Water-based aluminium paste is widely used to create metallic effects in automotive, industrial and plastic coatings. However, some coating manufacturers may find that the final coating does not have the expected metallic brightness after application.

Why does this happen? The problem may be related to dispersion, formulation, pigment orientation or application conditions.

1. Poor Dispersion

Poor dispersion is one of the common reasons for reduced metallic brightness.

If the aluminium flakes are not evenly distributed, pigment aggregation can occur. This can result in an uneven metallic appearance and reduced light reflection.

When using aluminium paste for water-based coatings, manufacturers should follow the recommended mixing process and avoid excessive shear that may damage the aluminium flakes.

2. Incorrect Formulation Compatibility

The compatibility between aluminium paste, resin and additives can directly affect the final appearance.

An unsuitable combination may cause poor pigment orientation, uneven distribution or changes in surface appearance.

For this reason, water-based aluminium paste should be tested with the actual resin and additive system before production.

3. Incorrect Pigment Orientation

Metallic brightness depends heavily on how aluminium flakes are arranged in the coating film.

When the flakes are well oriented and relatively parallel to the coating surface, light reflection can produce a brighter metallic effect.

Uneven orientation can reduce brightness and create a dull or inconsistent appearance.

Particle size, coating viscosity, application method and drying conditions can all influence pigment orientation.

4. Unsuitable Particle Size

Different aluminium flake sizes create different visual effects.

Finer flakes can provide a smoother and more uniform metallic appearance, while larger flakes can produce stronger sparkle and visual impact.

Therefore, the correct particle size should be selected according to the required coating appearance rather than simply choosing the finest available grade.

5. Application Conditions

Even when the aluminium paste itself performs well, application conditions can affect the final metallic effect.

Factors such as:

• Coating viscosity
• Spray pressure
• Film thickness
• Drying conditions
• Application method

can influence aluminium flake orientation and surface appearance.

Manufacturers should therefore evaluate water-based aluminium paste under actual application conditions.

How to Improve Metallic Brightness?

If a water-based coating shows insufficient metallic brightness, manufacturers can check the following:

1. Confirm that the aluminium paste is suitable for water-based coatings.
2. Check the dispersion process and mixing conditions.
3. Evaluate resin and additive compatibility.
4. Check particle size and pigment concentration.
5. Review application and drying conditions.
6. Compare the coating appearance using different aluminium paste grades.

Testing these factors systematically can help identify the main cause of brightness loss.

Conclusion

The metallic brightness of water-based aluminium paste depends on more than the pigment itself. Dispersion, formulation compatibility, particle size, pigment orientation and application conditions can all affect the final appearance.

For manufacturers using aluminium paste for water-based coatings, testing the complete coating system is essential for achieving a consistent and bright metallic effect.