Offset, flexographic (flexo), and gravure are the three dominant printing processes, and each imposes distinct pigment requirements rooted in their fundamentally different ink transfer mechanisms. Offset transfers ink via a series of rollers onto a lithographic plate, demanding high-viscosity paste inks (10–50 Pa·s) with pigments that resist water emulsification. Flexo uses a raised-relief photopolymer plate and anilox roll metering, requiring low-viscosity solvent- or water-based inks (0.05–0.5 Pa·s) with fast solvent release. Gravure etches ink into recessed cells on a chrome-plated cylinder, demanding the finest pigment dispersions (<0.1 µm aggregates) in ultra-low-viscosity inks (0.02–0.2 Pa·s) to prevent cell clogging during high-speed doctoring.

Process & Pigment Parameter Comparison

Parameter	Offset Lithography	Flexography	Gravure
Ink Transfer Mechanism	Planographic — ink transferred via series of rollers; image and non-image areas on same plate plane separated by water/fountain solution	Relief — raised image areas on flexible photopolymer plate pick up ink from anilox roll cells	Intaglio — recessed cells etched into chrome cylinder; doctor blade removes excess; substrate draws ink from cells under pressure
Ink Viscosity Range (Pa·s)	10–50 (high-viscosity paste ink)	0.05–0.5 (low-viscosity liquid ink)	0.02–0.2 (ultra-low-viscosity liquid ink)
Typical Pigment Particle Size (µm)	0.05–0.5 (moderate dispersion; paste vehicles are more forgiving)	0.05–0.3 (fine dispersion needed for anilox cell transfer; ~4–8 µm anilox cell depth)	<0.1 (ultra-fine dispersion essential — particles must be <10% of typical 5–30 µm cell depth for clean doctoring)
Pigment Loading (% in ink)	12–25% (high loading due to ~1.5–3 µm ink film thickness)	8–18% (balanced for low-viscosity system; typical film 2–4 µm)	6–15% (lower loading; extremely thin film ~0.5–2 µm dried)
Ink Film Thickness (µm, dry)	1.5–3.0	2.0–4.0	0.5–2.0
Solvent System	Mineral oils (high-boiling aliphatics), vegetable oil esters, alkyd resins — oil-based paste; water-based variants growing	Ethanol, ethyl acetate, n-propanol, water — fast-evaporating solvents; UV-curable variants for labels	Toluene (declining), ethyl acetate, MEK, ethanol — very fast-drying; water-based gravure for flexible packaging
Drying Mechanism	Oxidative polymerization + absorption into substrate (heatset: evaporation + resin setting at 120–160°C)	Solvent evaporation only (interstation dryers at 40–70°C); UV-curable for specialty labels	Solvent evaporation (high-volume dryers at 50–80°C); multiple interstation drying zones
Typical Pigments Used	PY12, PY13 (diarylide yellows); PR57:1 (Calcium Lithol Rubine — the workhorse process magenta); PB15:3 (phthalo blue); PBk7 (carbon black)	PY14, PY83 (diarylide yellows with better solvent resistance); PB15:3 (phthalo blue); PR57:1; PR48:2 (lake reds); PW6 (TiO₂ white)	PY12 (solvent-soluble yellow grades); PR57:1 (in toluene/ethyl acetate systems); PB15:3 (predispersed micro-pigment grades); PR122 (quinacridone for high-end packaging)
Substrate Compatibility	Paper, paperboard, coated papers — limited to absorbent or primed surfaces	Paper, corrugated board, flexible films (PE, PP, PET), labels, foil, non-wovens — widest substrate range	Flexible films (PE, PP, PET, PA), foil, laminates, coated paper, decorative papers, wall coverings
Print Resolution (lpi)	133–200 lpi (commercial); up to 300 lpi for high-end sheetfed	100–175 lpi (typical); lower than offset due to flexo dot gain (~15–25% physical dot gain)	150–300 lpi (highest image resolution among the three; continuous tone capability via cell depth variation)
Running Speed (m/min)	Sheetfed: 10,000–18,000 sheets/hr; Web offset: 300–900 m/min	150–600 m/min (wide web); up to 250 m/min (narrow web labels)	200–600 m/min (publication); 100–400 m/min (packaging)
Relative Ink Cost	$$ (moderate — high pigment loading but lower-cost vehicles)	$ (lowest ink cost per print — low viscosity reduces vehicle cost; moderate loading)	$$$ (highest ink cost per kg — ultra-fine pigment dispersion plus specialty resins; offset by thinner film)
Critical Pigment Requirements	Water resistance (fountain solution); moderate dispersion; low abrasion on plate; heat stability for heatset (up to 160°C)	Excellent solvent resistance (ethanol/acetate); low viscosity build; no plate swelling; fast solvent release	Ultra-fine particle size distribution; absolute freedom from aggregates >1 µm; no abrasion on doctor blade; excellent solvent wetting

Process-Specific Pigment Selection

Offset Lithography — Paste Ink, Water Balance

Offset lithography is unique in requiring the pigment to resist water emulsification from the dampening (fountain) solution. The pigment is dispersed in a high-viscosity resin-oil vehicle (10–50 Pa·s) and transferred to the plate at film splits measured in microns. PR57:1 Calcium Lithol Rubine (CI 15850:1) is the iconic offset process magenta — its strong bluish-red shade and modest cost ($8–12/kg) have made it the global standard for CMYK process magenta in sheetfed and web offset. Key offset pigment requirements:

• Water resistance: The pigment must not bleed into the dampening solution — this rules out many water-sensitive azo grades
• Moderate dispersion: Offset inks are milled on three-roll mills; extremely fine dispersion is unnecessary since film thickness is 1.5–3 µm
• Low abrasion: The pigment must not abrade the aluminum lithographic plate — irregular hard particles shorten plate life
• Heat stability: Heatset web offset inks flash-dry at 120–160°C; pigments must survive this without color shift (PY12 is borderline at 160°C)
• Typical formulation: CMYK offset uses PY13 (yellow, CI 21100), PR57:1 (magenta), PB15:3 (cyan, CI 74160), and PBk7 (black, CI 77266)

Flexography — Low Viscosity, Fast Solvent Release

Flexo requires low-viscosity inks (0.05–0.5 Pa·s) that transfer cleanly from anilox cells to a raised photopolymer plate, then to a wide range of substrates. The anilox roll contains millions of laser-engraved cells (typically 200–800 lines/cm, 4–8 µm depth) that meter a precise ink volume. PY83 diarylide yellow (CI 21108) is a workhorse flexo pigment due to its good solvent resistance and strength in alcohol/ester systems. Key flexo pigment requirements:

• Excellent solvent resistance: Flexo ink vehicles are ethanol, ethyl acetate, or n-propanol-based — the pigment must not dissolve or recrystallize in these solvents
• Fine particle size: Particles should be finely dispersed (<0.3 µm) to transfer cleanly from anilox cells without clogging or bridging
• Fast solvent release: The pigment surface should not retain solvent, which would cause residual odor in food packaging (critical for gravure and flexo both)
• No plate swelling: The pigment must be chemically inert toward the photopolymer plate material; reactive grades cause plate degradation
• Key flexo pigments: PY14 (CI 21095, greenish-yellow), PY83 (CI 21108, reddish-yellow), PR48:2 (CI 15865:2, calcium lake red), PB15:3 (universal cyan), PBk7 (black)

Gravure — Ultra-Fine Dispersion, Zero Aggregates

Gravure demands the most stringent pigment requirements of any printing process. Ink fills microscopic cells etched into a chrome cylinder (5–30 µm depth, 20–80 µm width), and a steel doctor blade wipes the cylinder surface clean at 200–600 m/min. Any pigment particle or aggregate larger than ~1 µm will score the doctor blade, create print streaks, or clog cells — all catastrophic at production speed. PR57:1 and PY12 are common in publication gravure, while PR122 quinacridone magenta enters high-end packaging gravure for its unmatchable color purity. Key gravure pigment requirements:

• Ultra-fine particle size distribution: Primary particles <0.1 µm with zero aggregates above 1 µm; typically achieved via bead-mill dispersion to Hegman grind gauge reading >7 (NS scale) or >6 (μm scale)
• Excellent solvent wetting: The pigment must be easily dispersible in the gravure solvent system (toluene, ethyl acetate, MEK, or ethanol) without re-agglomeration
• Low abrasivity: Mohs hardness of the pigment must be well below that of chrome (Mohs 8.5) to prevent doctor blade scoring — PB15:3 and organic pigments generally pass; avoid crystalline inorganics
• No re-crystallization: During high-speed drying (50–80°C interstation dryers), pigment must remain in its dispersed crystal form without Ostwald ripening
• Packaging gravure pigments: PR122 (quinacridone, CI 73915), PB15:3, PG7 (CI 74260), PY12 (solvent-grade, CI 21090), PR57:1 (CI 15850:1)

Pigment Universality: What Works Across All Three?

Pigment	CI Number	Offset Performance	Flexo Performance	Gravure Performance
PB15:3 — Phthalocyanine Blue	CI 74160	Excellent — standard offset cyan; water-resistant; heat-stable to 300°C	Excellent — good solvent resistance; disperses well in ethanol/acetate systems	Excellent — available in predispersed chip grades for ultra-fine gravure dispersion
PR57:1 — Calcium Lithol Rubine	CI 15850:1	Excellent — the global standard for offset process magenta	Good — requires careful solvent system to prevent bleeding; widely used	Good — fine dispersion grade needed; some bleeding risk in acetate systems
PY12 — Diarylide Yellow AAA	CI 21090	Excellent — standard offset process yellow; strong, clean shade	Moderate — solvent resistance limitations in alcohol systems; PY14 or PY83 preferred	Fair to good — requires low-solubility grade; recrystallization risk in pure solvent systems
PBk7 — Carbon Black	CI 77266	Excellent — universal offset black; high jetness from furnace grades	Excellent — fine particle grades (20–30 nm) for flexo; can raise viscosity	Good — requires de-aggregated grade; viscosity build can be an issue at high loading

Frequently Asked Questions

Why can’t I use the same pigment across all three printing processes?

While some pigments like PB15:3 are truly universal, most pigments require process-specific grades because the dominant failure mode differs across processes. In offset, a pigment that bleeds into fountain solution causes tinting and ink/water imbalance — PR57:1 is fine but many water-sensitive azo reds fail. In flexo, a pigment with poor solvent resistance dissolves into the ethanol/ethyl acetate vehicle, causing shade drift and plate contamination — PY12 fails where PY83 succeeds due to higher molecular weight and reduced solubility. In gravure, a pigment with aggregates >1 µm (perfectly acceptable in offset’s 3 µm film) will score the doctor blade, clog cells, and cause catastrophic print defects — the identical chemistry must be dispersed to far finer particle size. Additionally, the surface treatment (rosination, surfactant coating) that optimizes wetting in an offset oil-based vehicle may be incompatible with flexo’s alcohol-based or gravure’s ester-based solvent systems. You can use the same pigment chemistry across all three, but you typically need a process-specific grade with adjusted particle size distribution and surface treatment.

Which printing process is most forgiving for pigment selection?

Offset lithography is the most forgiving process for pigment selection. The high-viscosity paste ink system (10–50 Pa·s) suspends larger pigment particles effectively; the 1.5–3 µm dry film thickness tolerates moderate dispersion quality; and the oil/alkyd vehicle is chemically milder than the aggressive solvent systems used in flexo and gravure. Offset can successfully use pigments with particle sizes up to 0.5 µm that would be catastrophic in gravure. At the opposite extreme, gravure is the most demanding — the combination of ultra-low viscosity (0.02–0.2 Pa·s), microscopic cell dimensions, and high-speed doctor blade wiping means that pigment dispersion quality directly determines whether the press runs or stops. A single aggregate above 1 µm can produce visible streaks across an entire print run. For new pigment development, start with offset-grade dispersion, prove coloristic performance, then invest in the finer dispersion needed for flexo and gravure grades.

How does the shift from solvent to water-based inks affect pigment selection?

The ongoing shift from solvent-based to water-based inks, driven by VOC regulations, significantly changes pigment requirements — particularly for flexo and gravure. Water-based inks require pigments with excellent alkaline resistance (water-based systems are typically pH 8.5–9.5 via ammonia or amines). Pigments like PR57:1 (Calcium Lithol) bleed severely at alkaline pH, making them unusable in water-based flexo — formulations pivot to PR122 quinacridone or PR146 naphthol reds instead. Additionally, water’s high surface tension (72 mN/m vs. ethanol’s 22 mN/m) makes pigment wetting more difficult, requiring specific hydrophilic surface treatments on pigment particles. Pigments that performed excellently in solvent-based systems (e.g., PY12 in toluene gravure) may fail entirely when converted to water-based gravure due to re-agglomeration, poor wetting, or alkaline sensitivity. CB15:3 phthalocyanine blue is one of the few pigments that transitions seamlessly between solvent and water systems, which contributes to its dominance across all print processes.