русский
Español
Français
Home / News / Industry News / Epoxy Floor Coating — Why Are Some Areas Darker and Others Lighter After Application?
Industry News
Epoxy Floor Coatings · Industrial Floors · Coloured Floor Systems
After epoxy floor coating is applied, a relatively common phenomenon is frequently encountered: clearly using the same batch of coating, fully stirred before application — but the finished floor is not a uniform colour. Some areas are darker, some lighter; some positions look mottled, and colour differences become more obvious when the light direction changes. Simply attributing this to "non-uniform application" often fails to truly solve the problem. Epoxy floor colour differences between areas may be related to pigment dispersion, flooding and colour mottle, substrate absorption, and the film formation process — in addition to application film thickness differences.
1
Same Bucket of Coating — Why Still Have Colour Differences After Application?
Coating state in the bucket does not equal the state after application. If pigment dispersion stability in the system is insufficient, slight flocculation or local concentration differences may appear after standing. Even if stirred before application, if a fully uniform state was not achieved, the composition of coating taken from different positions may have subtle differences — ultimately forming areas of uneven depth in the film.
2
Why Does Poor Pigment Dispersion Directly Affect Colour?
Epoxy floors have relatively high requirements for colour uniformity. Pigment particles that are not fully dispersed easily form larger agglomerates. These agglomerates not only affect colour intensity — they may also change how the film reflects light. Therefore, even if the overall formulation pigment addition amount has not changed, as long as the pigment dispersion state changes, the final visual effect may show differences. In high-pigment-concentration coloured floor systems, the matching between dispersant, resin, and pigment is particularly important.
3
Why Does Flooding and Colour Mottle Appear?
If there are differences in migration speed between different pigments during the film drying process, flooding or colour mottle may be produced. The coating looks uniform in colour right after application, but as the film gradually levels and cures, some pigments redistribute. Different surface areas develop different pigment compositions — visually appearing as uneven depth. In large-area floor application, this problem is especially obvious because different areas may have subtle differences in application speed, film thickness, temperature, and flow state.
4
Why Do Thicker Areas Look Darker with the Same Colour?
Film thickness is also an important source of floor colour differences. With the same colour coating, different film thicknesses produce different degrees of hiding and light reflection. Thin-film areas may show slight show-through, allowing the substrate colour to affect the final visual effect. Thicker positions usually have more saturated colour. If scraping, rolling, or spraying during application is not uniform, different areas may have film thickness differences — causing colour inconsistency.
5
Different Substrate Conditions May Also Cause Colour Shade Changes
The final colour of an epoxy floor is not completely determined by the topcoat alone. If substrate treatment is inconsistent, the absorption capability of different areas may also differ. If some areas have higher moisture content, or penetrating primer penetration differs, this may affect the film formation state of subsequent coatings. If local substrate absorption is stronger, the thickness and surface state of the film may also change accordingly — producing different visual effects with the same topcoat applied in different positions.
6
Why Can Different Application Speeds Also Cause Colour Differences?
In large-area floor application, it is difficult to complete all areas at exactly the same time. Areas applied first and areas applied later have different open times. During the process from application to leveling and curing, the coating is sensitive to temperature, humidity, and ventilation. If application state differences between areas are large, the film surface flow and drying speed may differ. Temperature changes in particular can further amplify this difference.
7
Why Does the Dispersant Also Affect Final Colour?
In coloured epoxy floor systems, the dispersant not only affects whether pigment can be broken apart — it also affects the stable state of pigment during storage and film formation. If compatibility between dispersant, resin, and pigment is insufficient: initial colour may be normal → storage brings re-coarsening → application causes flooding → final area colour difference results. If the dispersion system is relatively stable and pigment can maintain uniform distribution, the probability of local colour change during application is also reduced.
8
How to Diagnose — When Floor Colour Difference Already Appears?
If colour difference is related to film thickness, prioritise checking application uniformity. If colour appears as cloud-like or stripe-like variation, focus on flooding and pigment migration. Check substrate state — compare moisture content, roughness, and primer condition of different areas. Check coating storage state — confirm whether it was fully stirred before application. Check the dispersion system — if obvious differences exist between batches or pigment systems, re-evaluate the matching between dispersant, resin, and pigment.
Summary
Epoxy floor area colour differences are not necessarily a pigment addition amount problem. Film thickness differences, substrate state, pigment dispersion stability, flooding, and application environment changes can all cause final colour shade inconsistency. Especially in large-area application, the coating goes through dynamic changes from stirring and application through to final curing. Therefore, solving epoxy floor colour differences cannot only focus on "whether the colour was mixed accurately" — it is also necessary to ensure that pigment always maintains a stable, uniform distribution throughout storage, application, and film formation.
Film thickness difference is a common source of area colour difference
Pigment dispersion stability determines colour uniformity
Flooding redistributes pigment during film drying
Substrate condition affects coating absorption and film formation
Application speed and environment affect colour consistency
Dispersant system matching affects long-term colour stability
Frequently Asked Questions
Is flooding in coloured epoxy floor coatings always caused by pigment migration — or can it also come from other component separation?
Flooding in coloured epoxy floors can arise from multiple mechanisms: pigment-pigment density and particle size differences causing differential settling or surface migration; filler-resin incompatibility causing localised filler-rich zones; and surfactant or additive surface migration creating local surface tension differences that produce Bénard cell patterns visible as cloud-like colour mottle. Diagnosis of the specific mechanism matters because the corrective action differs: pigment migration is addressed through dispersant optimisation; additive migration through type or dosage adjustment; and density-driven settling through viscosity and flow adjustment.
Can flooding in epoxy floor systems be improved by adjusting mixing ratio of Part A and Part B?
In two-component epoxy systems, the mixing ratio affects viscosity, cure speed, and the open time during which pigment redistribution can occur. An off-ratio mix — either excess resin or excess hardener — may affect viscosity and extend or shorten the open time, potentially worsening or improving flooding depending on the specific system. However, deliberately departing from the specified ratio to control flooding is not recommended, as it compromises film properties. Flooding should be addressed through dispersion system optimisation, not through ratio adjustment.
