DH-6740S: Prevent Pigment Re-Coarsening in Waterborne Colorants

Waterborne Color Paste Passed Fineness Testing — Why Is It Going Gritty in Storage

2026/06/26

Waterborne Colorant Dispersant Technology

Re-coarsening — the gradual return of dispersed pigment particles toward a coarser, more agglomerated state after grinding — is one of the most common storage stability failures in waterborne colorants and pigment pastes. It appears as a gritty texture, increased viscosity, reduced color development, or hard sediment that returns even after the pigment was ground to specification. And unlike many formulation problems, it gets progressively worse the longer the product sits.

What Re-Coarsening Actually Means

During milling, mechanical energy drives pigment particles apart and creates a freshly dispersed state. Without an effective dispersant stabilizing this state, the particles remain thermodynamically driven to reduce their total surface energy — which means coming back together. This is not a slow or exceptional process; it begins as soon as mechanical shearing stops, and it accelerates when the pigment has high surface area (fine organic pigments, carbon black) or when the stabilizing system is insufficiently matched to the specific pigment surface chemistry.

Common Symptoms in Waterborne Colorant Systems

Poorly Stabilized System

High grind viscosity — slow milling, energy-intensive processing
Poor color development — pigment not fully dispersed to primary particles
Re-coarsening during storage — fineness increases after milling stops
Settling and hard sediment on extended storage
Color inconsistency between colorant batches
Compatibility issues when let-down into different resin systems

Optimized with DH-6740S

Lower grind viscosity — faster milling, better processing efficiency
Full color development from better primary particle separation
Stable fineness maintained through storage
Reduced settling and easier re-dispersion if sediment forms
More consistent color from batch to batch
Good adaptability to resin-free and resin-containing colorant architectures

DH-6740S Nonionic Wetting & Dispersant

DH-6740S is a nonionic wetting and dispersing additive for waterborne colorant and coating systems. By improving the wetting state between pigment particles and the aqueous medium, it helps particles enter the dispersion phase more readily during milling and — critically — remain in that dispersed state during storage. The result is a lower grind viscosity, better color development, and a more stable colorant that resists re-coarsening and settling over time.

Pigment Wetting	Improves the interfacial wetting between pigment particles and the waterborne medium, reducing the energy required for dispersion
Milling Efficiency	Lower grind viscosity reduces milling time and energy input while reaching equivalent or finer fineness
Re-Coarsening Resistance	Stabilizes dispersed particles against re-agglomeration during storage, maintaining fineness over time
Settling Control	Reduces the rate of sedimentation and helps maintain a soft, easily re-dispersible sediment if settling occurs
Color Development	Better primary particle separation translates directly into improved color strength and masstone
System Compatibility	Good adaptability to both resin-free and resin-containing colorant systems, supporting a range of waterborne coating architectures

Pigment Types

DH-6740S has been evaluated across both inorganic pigments (titanium dioxide, iron oxides, mixed metal oxides) and organic pigments — including high-surface-area types such as phthalocyanines and carbon black that are particularly prone to re-coarsening.

Frequently Asked Questions

Why do organic pigments and carbon black re-coarsen more readily than inorganic types?

Organic pigments and carbon black have significantly higher surface area per unit mass, meaning the thermodynamic driving force toward re-agglomeration is much stronger. They also have surface chemistries that are less inherently compatible with aqueous media, which reduces the natural stabilization that larger, denser inorganic particles may have.

Can DH-6740S be used in resin-free universal colorant systems?

Yes — it is designed with compatibility in both resin-free and resin-containing colorant architectures, which is why it can be evaluated across the range of waterborne colorant designs currently in use.

Will it affect the compatibility of the colorant when let-down into different paint bases?

Nonionic dispersants generally have broader compatibility profiles than ionic types, which is a practical advantage when a colorant needs to be compatible with multiple paint bases. Compatibility testing with specific target systems is still recommended.

Can it reduce the grinding time for carbon black or phthalocyanine blue?

By reducing grind viscosity and improving particle wetting efficiency, it can support shorter milling cycles to reach a given fineness target — the actual time saving depends on equipment, pigment type, and concentration.

Key Takeaway

Re-coarsening in waterborne colorants is a dispersant stabilization problem — the freshly milled dispersion state is not thermodynamically stable without an additive actively preventing re-agglomeration.

DH-6740S improves wetting and dispersion efficiency across inorganic and organic pigments
Supports lower grind viscosity, better color development, and more stable fineness through storage
Reduces settling rate and maintains easy re-dispersion in the event of sedimentation
Compatible with both resin-free and resin-containing waterborne colorant architectures

Experiencing re-coarsening, settling, or color development issues in your waterborne colorant or pigment paste? Request technical information and a sample of DH-6740S.