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Home / News / Industry News / Metallic Paint Dispersion Is Fine — Why Is the Metallic Effect Still Weak After Spraying?
Industry News
1
Aluminium Flake Already Dispersed — Why Is Metallic Effect Still Insufficient?
For metallic paint, "dispersed open" is only one part of the process. Aluminium flake is a flat pigment — the metallic effect ultimately presented is closely related to its arrangement state in the film. When large numbers of aluminium flakes can arrange relatively regularly along the film surface, light reflection is more concentrated, the film looks brighter, and metallic quality is more pronounced. If the arrangement is chaotic, even if the pigment has no obvious aggregation, light reflection becomes scattered — visually appearing grey, dull, and with insufficient metallic effect.
2
Film Flow State Changes Aluminium Flake Arrangement
After aluminium flake enters the film, it is not static. After spray application, the wet film goes through wetting, flow, leveling, and solvent evaporation — the aluminium flake also changes position and angle with the film state. If film flow is sufficient, flat aluminium flake has the opportunity to gradually tend toward a flatter state. But if the system flow state is inappropriate, the aluminium flake may not form a stable arrangement — resulting in inconsistent metallic effect between different areas.
3
Leveling Agent Is Not Better in Larger Amounts
The influence of leveling agent on metallic paint is quite special. An appropriate leveling system can improve film spreading, making the surface more flat, and helping reduce surface defects generated during application. But as leveling agent addition changes, system surface tension and film flow state may also change — and for metallic paint containing aluminium flake, these changes may further affect aluminium flake arrangement. Therefore, leveling agent evaluation for metallic paint cannot only look at film flatness — the spray board should also be observed from different angles to check metallic flake orientation.
4
Dispersant Primarily Addresses "How Aluminium Flake Stably Exists"
Dispersant also affects the final appearance of metallic paint. For aluminium flake systems, dispersant needs to be matched with the resin, solvent, and aluminium flake surface state. If wetting is insufficient, aluminium flake easily develops local aggregation, causing non-uniform pigment distribution in the film. But if the dispersion system acts too strongly on the aluminium flake surface, it may also change the arrangement state. Therefore, dispersant for metallic paint cannot be simply understood as "stronger dispersing capability is better" — matching with the entire formulation matters more.
5
Wetting State Changes May Also Change Metallic Effect
Metallic paint is relatively sensitive to wetting state. If the wetting state of aluminium flake in the resin system is not ideal, local aggregation or non-uniform distribution readily appears. After wetting agent addition, system surface tension and film spreading state may also change. This easily produces a common situation: the intent is to improve wetting for more uniform aluminium flake distribution, but the metallic effect changes instead. Therefore, when adjusting wetting agents, it is not enough to only observe storage stability or paint state — spray board observation is also needed.
6
Different Film Thickness — Metallic Effect May Also Differ
Metallic paint is typically sensitive to film thickness changes. The same formulation at different film thicknesses shows changes in aluminium flake arrangement state, film transparency, and light reflection. Thin film may show insufficient coverage; thick film extends the flow time and the aluminium flake re-arrangement process also changes. Therefore, when evaluating the formulation's metallic effect, it is best not to use only one film thickness — multiple film thicknesses can be compared to observe metallic effect, light-dark changes, and front-side-view effect differences.
7
Different Application Method — Why Does the Same Bucket of Paint Give Different Results?
Beyond formulation factors, application conditions cannot be overlooked. Spray pressure, spray distance, spray width, traverse speed, atomisation state, and flash-off time can all change the wet film formation process. After the atomisation state changes, droplet size and wet film formation speed also change, subsequently affecting aluminium flake arrangement. Therefore, if "the same paint gives different metallic effect when sprayed by different operators," this does not necessarily mean the coating itself changed — the application parameters also need to be checked.
8
How to Diagnose Weak Metallic Effect and Adjust?
If grey, insufficient brightness, or weak metallic effect appears: first observe aluminium flake distribution — confirm whether obvious aggregation, flocculation, or local accumulation exists. Then check aluminium flake arrangement by observing spray boards from different angles to judge whether flakes can form a relatively stable arrangement state. Then adjust the dispersion system — not simply pursuing stronger dispersion. Re-evaluate the leveling agent — if metallic effect changes after changing the leveling agent or increasing the amount, focus on surface tension and film flow state. Check film thickness — compare multiple film thicknesses, avoiding misidentifying film thickness variation as a pigment problem. Then standardise application conditions before comparing formulations.
Summary
Metallic effect in metallic paint is not simply determined by the amount of aluminium flake. The state of the aluminium flake itself is only one part — dispersion, wetting, film flow, surface tension, film thickness, and application conditions may all affect the final metallic effect. When metallic paint shows "colour is right, but metallic effect is insufficient," rather than directly increasing aluminium flake, it is better to start from aluminium flake arrangement and the film formation process, then adjust in combination with dispersant, leveling agent, and wetting agent. What truly needs attention for metallic paint is not the action of any single additive, but the arrangement state that aluminium flake ultimately presents after the system has formed the film.
Frequently Asked Questions
Is the "face angle" vs "flop angle" measurement useful for diagnosing aluminium flake orientation problems?
Yes — this measurement directly quantifies the characteristic that pearl and metallic orientation problems manifest as. The face angle (measured at near-perpendicular illumination and observation) gives the brightness when flakes are viewed at the alignment angle; the flop angle (measured at near-grazing observation) gives the brightness at the poorest angle for aligned flakes. The ratio between these values — the flop index — quantifies the directionality of the metallic effect. Low flop index indicates poor flake orientation or chaotic arrangement. Comparing flop index before and after formulation or process changes is a quantitative tool for evaluating whether the change improved or worsened flake orientation.
Does the aluminium flake grade (cornflake vs silver dollar type) affect how sensitive the metallic effect is to leveling and flow conditions?
Yes significantly. Silver dollar type aluminium flakes have a smooth, regular circular morphology with high reflectivity and produce sharp, high-flop metallic effects — but this also makes them more sensitive to orientation disruption during film flow, as any angular deviation from the flat position reduces their specular reflectivity substantially. Cornflake type aluminium has an irregular, rougher morphology that produces a more diffuse sparkle and lower flop — and is correspondingly less sensitive to the precise orientation conditions during film formation. Formulations requiring very high metallic clarity and flop should use silver dollar grades but require more careful leveling system management.
