Select a pigment grade that meets the required print appearance within the ink’s processing, viscosity and stability limits. In waterborne acrylic flexographic and gravure inks, first compare candidates in the existing formulation to establish whether a direct replacement is feasible. Treat changes to dispersant, grinding resin or pigment loading as reformulation. For carbon black, assess aggregate structure and surface chemistry alongside particle size before choosing a finer grade. Make the final selection at the required printed color, after confirming that the chosen combination remains acceptable through binder letdown, storage and printing.

This guide covers organic pigments and pigment-grade carbon black. Inkjet, conductive and UV-curing inks require separate qualification. Acceptance limits must come from the intended ink, substrate and printing process.

Define the Optical Target and the Candidate Grade

For colored inks, specify the required shade and whether transparency or hiding is part of the target. For black inks, distinguish a deep solid black on coated paper or film from the printed density required on absorbent stock.

Specify whether black-ink acceptance concerns full-shade appearance, undertone, tinting strength in a white mixture or printed reflection density. If more than one is required, define a separate test and acceptance criterion for each.

Identify each candidate by its Colour Index designation, exact commercial grade and delivery form. Record declared surface treatment and, where relevant, crystal modification. For a supplied dispersion, obtain pigment content and available carrier-resin and additive information before calculating an equivalent replacement.

Surface treatment belongs in the comparison. BYK’s practical guidance explains that dispersing additives interact with the treated pigment surface and recommends considering alternative surface treatments when grinding results are unsatisfactory. A failed first grind therefore identifies a problem with the tested combination; it does not establish that every grade of that pigment is unsuitable.

Compare Carbon Black Structure Before Pursuing More Jetness

Carbon black contains fused primary particles assembled into aggregates. Dispersion breaks down agglomerates rather than converting every grade into isolated primary particles.

Cabot’s printing-ink selection guide describes three distinct selection variables. Smaller primary particles generally offer greater jetness potential with more demanding dispersion and viscosity behavior. Lower aggregate structure can reduce viscosity impact while making dispersion harder. Oxidative surface treatment can improve wetting and flow in compatible vehicles.

Use these trends to choose the next controlled comparison. If blackness is already adequate but flow is restrictive, include a lower-structure candidate with a comparable optical target. If wetting or stability is inadequate, compare surface treatment or dispersant chemistry. These are proposed screening paths; grades differing in several attributes cannot isolate one attribute’s contribution.

Request specific surface area in m²/g and oil absorption number, or OAN, in mL/100 g, with the supplier’s methods. Orion’s technical data guide reports surface area and the structure-related OAN separately. Use them to describe candidates; determine actual dispersant demand through the formulation trials below.

Keep substrate effects separate from millbase flow. Cabot describes higher-structure blacks improving coverage and optical density on porous newsprint in aqueous flexographic inks. This specific holdout benefit does not establish the preferred grade for coated paper or film.

Separate Direct Replacement from Reformulation

Test the existing formulation first

Replace the reference pigment on an equal dry-pigment-mass basis. Keep grinding resin, dispersant chemistry and active dosage, water quality, neutralizer and letdown package unchanged.

Use the same milling setup and document temperature, time, media conditions and energy where available. Compare samples after the same cooling and conditioning procedure. Do not thin one candidate to match the reference viscosity during this stage.

This trial tests compatibility with the existing formula and process. Failure excludes a straightforward replacement under those conditions. A candidate requiring a different additive package can enter a separately identified reformulation trial.

For supplied dispersions, account for their water, carrier and additives. If composition cannot be balanced from available information, describe the result as a comparison of formulated concentrates rather than an isolated pigment substitution.

Define what may change

For reformulation, state whether changes to dispersant chemistry, active dosage, grinding resin or pigment loading are allowed. Identify the reference formulation and acceptance criteria before optimization.

Keep binder-containing and binder-free grinding routes separate in the trial record. A change of route changes the combination being qualified, so its result cannot be used to claim compatibility with the unchanged formulation.

Normalize Dispersant Demand and Establish Usable Loading

Check both the numerator and denominator of each addition recommendation. Additive as supplied on total grind, additive as supplied on pigment and active dispersant on pigment are different reporting bases.

For example, Evonik’s TEGO Dispers 761 W technical data sheet distinguishes binder-free grinding from use alongside grinding resin and expresses its addition guidance on the grind. Convert the basis before comparing it with a pigment-based recommendation.

For a defined active content:

Active dispersant on pigment (%) = 100 × additive mass × active mass fraction ÷ dry pigment mass.

Use the supplier’s active-content definition. Do not substitute a nonvolatile-solids result unless its relationship to active content has been established.

BYK’s dosage guidance cautions that surface-area or oil-absorption calculations are not generally reliable dosage predictors. Use an applicable supplier recommendation to define the initial laboratory range.

The following is a proposed comparison design. At a common dry-pigment concentration, prepare fresh grinds across the justified dosage range. Keep the resin package, water quality, target pH, addition sequence and milling procedure comparable. Balance carrier water and record changes in additive solids.

Sample during milling to determine whether coarse-material reduction and useful color development continue. Compare conditioned samples rather than hot mill discharge.

For promising combinations, prepare separate batches at increasing pigment concentrations within equipment and supplier limits. Keep the selected active-dispersant-to-pigment and grinding-resin-to-pigment ratios consistent; rebalance water. Resin and additive concentrations rise with pigment concentration, so this establishes the loading range of the complete millbase route.

Interpret the Results Before Changing the Grade

Use the following patterns as selection leads. They do not prove an adsorption mechanism or identify a unique root cause.

For systems relying on steric stabilization, BYK’s mechanism explanation identifies both pigment adsorption and compatibility of the protruding polymer chains with the surrounding vehicle. This provides a reason to test the complete letdown package even when the initial millbase is acceptable.

If thickening first appears at letdown, verify composition, solids, pH, temperature and entrained air against the reference. Where useful, compare a pigment-free vehicle blend or controlled aliquots with and without a suspected addition. Account for carrier and dilution differences.

A similar change in the blank identifies a vehicle contribution without excluding pigment instability. A stable blank alongside color loss or increasing coarse material in the pigmented ink strengthens the case for further dispersion investigation. Neither control alone proves the cause.

Use Measurements That Can Support the Decision

A grind gauge screens coarse particles or agglomerates. It does not establish the complete particle-size distribution, as stated in BYK-Gardner’s fineness-of-grind guidance. A satisfactory reading alone cannot confirm full dispersion or storage stability. media.byk-instruments.com

For viscosity, record the instrument, geometry or spindle, speed or shear rate, temperature, conditioning and reading time. Include flow and recovery measurements where relevant. BYK-Gardner’s rheometry guide explains why shear and time dependence, together with measurement geometry, affect interpretation.

For optical comparisons, keep instrument settings, backing, sample conditioning and drying conditions consistent. Measure shade, transparency or opacity, blackness or reflection density according to the actual target.

Define the dry-deposit comparison as well. Identical applicator settings do not establish equal deposited mass when solids and transfer differ. If deposit cannot be verified, report the optical result as performance under fixed application conditions, with that limitation.

Select the Final Formulation at the Required Print Appearance

Evaluate reformulated finalists at the required color on the intended substrate. One proposed basis keeps binder identity and binder solids per unit mass of finished ink constant, adjusts pigment loading to meet the target and balances with water. Record the resulting pigment content, binder-to-pigment ratio, active dispersant and total solids.

For carbon black, calculate active dispersant per unit mass of finished ink from final pigment content and the selected active-dispersant-to-pigment ratio. A higher requirement per gram of pigment does not by itself establish a higher requirement per kilogram of finished ink. The calculation must use the actual optimized formulations.

Carry finalists through defined storage and representative circulation or printing. Keep substrate, anilox or gravure-cylinder specification, speed and drying conditions fixed for the initial comparison. Record actual transfer or dry deposit where practicable. Document any setup changes required by a candidate.

Keep sealed storage separate from open circulation, recording temperature, evaporation and corrective additions. Check adhesion, rub or water resistance where required; meeting color and viscosity targets does not waive finished-film requirements.

Retain a direct replacement only when the unchanged formula and process pass the defined criteria. Treat an acceptable optimized combination as a reformulated option with documented implementation conditions. Exclude a candidate from this application when its usable range cannot satisfy the required appearance, flow, stability and film performance.

The next step is one matched reference-versus-candidate trial using the exact grades and permitted formulation route. ChemicalCell’s Pigments category supports initial material browsing; confirm grade identity and relevant aqueous application data before including a listed material in that trial.