Which dispersant should a formulator select for organic pigments in gravure inks? In medium-polarity solvent-based systems, polymeric dispersants compatible with both the pigment surface and the resin–solvent vehicle provide a starting point. Candidates should then be evaluated against color development, processing flow, storage stability and the active dosage needed to meet specification. A fresh grind-gauge reading or an attractive drawdown answers only part of the question. Selection requires a match to the formulation, rather than a universal product ranking.

Organic pigments illustrate this especially well. An additive that improves color development in a yellow ink may offer its clearest benefit in storage behavior when used with a red pigment. In a blue ink, the same additive may show little differentiation. Including carbon black and titanium dioxide in a screening program makes these application boundaries even clearer.

Different pigment surfaces create different challenges

Dispersion involves wetting, mechanical deagglomeration and stabilization. The liquid must penetrate agglomerates and displace air, milling must separate them, and the newly exposed surfaces must remain protected against reagglomeration. Identical grind-gauge readings do not establish identical particle-size distributions, color strength or storage behavior.

Organic pigments differ in crystal structure, surface functionality, specific surface area and surface treatment. Azo pigments, lakes, phthalocyanines and quinacridones therefore should not be selected for dispersion simply by color. Even pigments sharing a Color Index designation may require different additive levels when the grade or surface treatment changes.

For organic reds and yellows, formulation priorities often include color development, transparency and rheological stability. Phthalocyanine blues also demand attention to shade, color strength and compatibility after letdown. Carbon black introduces high surface area and aggregate structure; the objective is generally to separate agglomerates, rather than break every fused aggregate into primary particles. Titanium dioxide brings surface-treatment, hiding-power and settling considerations. These differences define the conditions under which a dispersant must function.

What an organic pigment dispersant needs to match

A polymeric dispersant needs pigment-affinic anchoring functionality and stabilizing chains compatible with the surrounding liquid. Adsorption holds the additive at the surface, while solvated chains provide steric separation. Insufficient anchoring can permit desorption; inadequate chain compatibility can weaken stabilization. A comb-like architecture or an amine value alone does not establish performance in a finished ink.

Dosage is equally important. Insufficient coverage can leave newly exposed surfaces vulnerable to reagglomeration. Excess unadsorbed additive may alter flow, foam, drying or film properties. A dosage ladder based on active dispersant relative to pigment is more informative than transferring one addition level between colors.

Why dispersant performance changes between gravure ink systems

The grinding resin can compete for pigment surfaces, and the letdown vehicle can change compatibility. Alcohol-to-ester balance, solvent evaporation and moisture can modify the liquid environment. Wetting agents, defoamers, waxes and other additives also belong in the final compatibility assessment. A stable millbase does not automatically remain stable after dilution or press circulation.

Addition sequence, predissolution, grinding media, energy input and temperature should be controlled. Easy flow alone does not demonstrate adequate dispersion: an ink containing coarse agglomerates may flow readily while delivering insufficient optical performance. Final validation should include cell transfer, resolubility, drying, substrate adhesion and, for laminating inks, lamination performance.

Application screening recommendations supported by ink test data

A polyurethane/PVC gravure-ink study conducted by Corechem in July 2025 compared three high-solids polymeric dispersants against an established market-brand benchmark and a no-dispersant control. The pigments were P35 carbon black, PR57:1 red, PY14 yellow, PB15:4 blue and grade 706 titanium dioxide. Table 1 connects each product to an application screening priority and its supporting observations. The subsequent discussion uses the designations A, B and C.

The technical data sheets describe all three as comb-structured polymeric dispersants. A and B are solvent-free solids with nonvolatile content of at least 99% and amine values of 25–35 mg KOH/g. C is a viscous liquid with stated active content above 99%. A is positioned for high-color carbon black, selected high-performance organic pigments and inorganic pigments. B additionally emphasizes alcohol/ester systems and heat-storage stability with selected organic reds. C focuses on organic pigments and carbon black. These descriptions establish screening candidates; they do not disclose identical molecular compositions or prove equal performance.

The additives were prediluted to 20% in ethyl acetate. Samples underwent a total of 60 minutes of glass-bead shaking, with cooling intervals, followed by letdown. Fresh-ink efflux time was measured with a No. 4 flow cup at 23 ± 1°C, and fineness with a 0–50 μm grind gauge. Diluted samples were drawn down on OPP and PET. Accelerated storage was conducted at 50°C for seven days. Values in seconds below are cup efflux times, not dynamic viscosity in mPa·s.

Table 1. Application screening starting points in the tested gravure inks

These are first-screen candidates for the same or similar formulations. Optical observations were visual, and values in seconds are cup efflux times. A change in pigment grade, binder or solvent combination requires renewed dosage and performance validation.

Figure 1. Initial grind-gauge fineness in μm. The reading indicates detectable coarse particles or agglomerates, not mean particle size. The yellow control matched several additive-containing samples at 12.5 μm, despite differences in visual optical performance.

Carbon black calls for a combined assessment. Fineness was 12.5, 17.5 and 15 μm for A, B and C, versus 15 μm for the benchmark and 30 μm for the control. Initial efflux times were 10.5–10.7 seconds for the three candidates and 10.9 seconds for the benchmark. C changed from 10.7 to 10.4 seconds after storage; the report also noted a small visual increase in gloss and jetness. This makes C a useful screening candidate, although it showed no clear initial optical advantage. The small time differences do not establish superiority across all storage criteria.

Red highlights storage-related flow changes. All four additive-containing inks reached 10 μm. Benchmark efflux time increased from 17.8 to 21.2 seconds, or 19.1%. A changed from 15.6 to 15.8 seconds, or 1.3%; B from 14.2 to 14.1 seconds, or −0.7%; and C from 16.3 to 17.6 seconds, or 8.0%. B merits priority when controlling efflux time is the main objective. A remains a candidate when the report's broader visual assessment is considered. Gloss showed no obvious difference from the benchmark, but this does not establish equivalence across optical properties. Red color strength with A warrants reassessment after storage.

Figure 2. PR57:1 red-ink efflux time before and after seven days at 50°C. Percentage change equals the after-minus-before difference divided by the initial value. The control's shorter time does not indicate better dispersion: its initial fineness was 22.5 μm.

Yellow shows a balance between optics and flow. A received favorable visual ratings relative to the benchmark for color development, transparency and gloss, while its initial efflux time was 15.3 seconds versus 14.1 seconds for the benchmark. B, at 14.4 seconds, was closer to the benchmark. C reached 10 μm, compared with 12.5 μm for the other groups, without achieving a corresponding advantage in every optical property. A is therefore a reasonable starting point for optical priorities, while B warrants screening when flow is emphasized.

Blue showed limited differentiation. All additive-containing inks reached 10 μm, with initial efflux times of 11.7–12.1 seconds. A and the benchmark both measured 11.8 seconds initially and 10.9 seconds after storage. Their transparency showed no obvious difference. A showed no clear color-strength advantage, so a replacement decision should include instrumental color and strength measurements at equal dry-film thickness.

Titanium dioxide requires a white-ink perspective. All additive-containing samples reached 10 μm. Initial efflux times for A, B and C were 11.6, 12.2 and 11.9 seconds, versus 12.5 seconds for the benchmark. After storage, these became 13.3, 14.1 and 13.7 seconds, versus 14.2 seconds. The report identified B as a white-ink candidate, although it did not give the shortest initial efflux time among the three. No clear advantage in whiteness or gloss was established. Hiding power, settling and lamination performance should help determine the final choice.

Evaluate storage as a separate performance requirement

Table 2. Cup efflux time in seconds, shown as initial → after seven days at 50°C. Small changes do not establish statistically significant differences.

The data do not produce one ranking that applies to every pigment. Red differentiated the additives most clearly in efflux-time drift. All white inks showed an increase, while most black, yellow and blue samples showed modest decreases. A decrease is not automatically evidence of improved stability; settling or other structural changes may also affect the result.

A storage program should track efflux time, fineness, color, gloss, separation, sediment and redispersibility under consistent sampling and temperature conditions. Seven days at 50°C is an accelerated screening condition, not a direct prediction of ambient shelf life. Ambient storage in the intended packaging, temperature cycling and press trials should follow before scale-up.

This screening study did not report replicate counts or error ranges, and optical comparisons were mainly visual. “No obvious difference” describes the relevant observation rather than statistically demonstrated equivalence. Similarly, improved fineness at a fixed milling time does not by itself prove a reduction in production milling time.

How dispersant solids and dosage affect gravure ink cost

Product price should be considered alongside supplied solids and the dose needed to meet the target. Active dispersant on pigment equals the mass of supplied dispersant multiplied by its active fraction, divided by pigment mass. Predilution must be included. Nonvolatile content should substitute for active content only when their relationship has been confirmed.

For example, adding 3 kg of a solution containing 20% active dispersant to 15 kg of pigment gives an active-on-pigment dose of 4%. This illustrates the calculation; it does not establish the study's final-ink addition rate. The original formulation lists grinding and letdown components, so an individual listed percentage should not be treated as a normalized finished-ink percentage.

High-solids supply reduces carrier brought in with the product, but solid or viscous additives may require dissolution and handling steps. Predilution solvent must be included in the formulation balance. High supplied solids alone therefore do not prove lower solvent use in the finished ink. Because all three candidates are high-solids products, optimized active dosage and process behavior are particularly important differentiators.

The useful economic measure is total cost per kilogram of ink meeting specification. It includes additive, pigment, resin and solvent costs, milling and adjustment, filtration losses, and storage-related rework. Screen at comparable active dosage, then optimize each candidate to the same color strength, printing flow and storage requirements. Potential pigment savings, higher solids or shorter milling should enter the cost model only after they have been demonstrated.

Turning a dispersant shortlist into a working formulation

For organic-pigment gravure inks, define the main formulation priority before shortlisting candidates. Start with A when yellow color development and transparency lead the brief. Examine B when lower, stable red-ink efflux time is central, while comparing A for the broader performance balance. A also provides a starting point for blue formulations seeking benchmark-like flow behavior. For carbon black and titanium dioxide, include C and B, respectively, among the candidates while retaining alternatives as controls. These recommendations arise from the specified formulations; they are not universal claims for every grade within a pigment class.

Build an active-dosage ladder, evaluate grinding, letdown, storage and printing, and calculate cost per kilogram of ink meeting specification. There is no perfect product for every system. Dispersion quality, supplied solids, actual dosage and storage behavior all belong in the selection decision.

Corechem Additives provides customized additive services. Engineers are welcome to discuss their pigment grades, resin and solvent composition, milling conditions and performance targets to identify a better-matched gravure-ink dispersion solution. For product and technical inquiries, visit the Corechem website.