Overview #
Metallic and pearlescent inks are among the most specification-sensitive materials we work with — the difference between a flat, dull metallic and a genuinely luminous finish often comes down to particle size selection and the print process used to lay it down. Brand owners in cosmetics, spirits, premium food, and consumer electronics packaging ask us about these inks constantly, usually after a disappointing sample from another supplier. The core technical issue is this: metallic and pearlescent pigments are platelet-shaped particles that need to lie flat and parallel to the substrate surface to reflect light correctly — and every process decision, from ink viscosity to screen mesh count to substrate smoothness, either supports or destroys that orientation.
Pigment Particle Size: The Foundation of Reflectivity #
The optical performance of metallic and pearlescent inks is governed almost entirely by particle size distribution. Aluminium flake pigments for metallic inks typically range from 5 µm to 60 µm in median diameter. Pearlescent pigments — usually mica platelets coated with titanium dioxide or iron oxide — run from 5 µm to 200 µm depending on the effect grade.
We classify these into three functional tiers on our production floor:
- Fine grade (5–15 µm): Highest printability, smoothest lay, suitable for offset and flexo. Lower specular reflectivity — produces a satin or brushed-metal appearance. Typical reflectance values of 60–75% at 45° geometry (measured per ASTM E1164).
- Medium grade (15–40 µm): Balanced between printability and sparkle. Our most-used range for folding carton and label work. Reflectance 75–88%.
- Coarse grade (40–100 µm+): Maximum sparkle and glitter effect. Requires screen printing or gravure — offset rollers shear and fracture particles above ~25 µm. Reflectance can exceed 90% specular at 45°.
Particle fracture is the single most common cause of metallic ink disappointment. When a brand partner sends us a reference sample with a high-sparkle metallic and asks us to match it in offset, we have to explain that the particle size in that reference is almost certainly above 25 µm — and offset will destroy it. We either switch to screen or reformulate with a fine-grade pigment and accept a lower-sparkle result.
Process Comparison: Offset, Screen & Gravure for Metallic/Pearlescent Inks #
This is where most production decisions get made. Each process has hard limits on particle size, ink film thickness, and achievable reflectivity.
| Parameter | Sheet-Fed Offset | Screen Printing | Gravure |
|---|---|---|---|
| Max usable particle size | ~20–25 µm | 80–120 µm (mesh dependent) | 30–50 µm |
| Ink film thickness (wet) | 2–4 µm | 15–50 µm | 4–12 µm |
| Achievable reflectance (45°) | 60–80% | 80–95% | 70–88% |
| Register accuracy (our line) | ±0.10–0.15 mm | ±0.3–0.5 mm | ±0.15–0.25 mm |
| Substrate requirement | Coated board ≥200 GSM | Flexible or rigid, wide range | Film or coated board |
| Typical application | Folding cartons, labels | Rigid boxes, luxury labels | Flexible packaging, labels |
| Relative unit cost | Low–Medium | Medium–High | Medium (high tooling) |
Screen printing is the only process that can deliver the full particle size range without mechanical shear damage. On our screen lines, we use 80–120 mesh stainless steel screens for coarse metallic inks — below 80 mesh the ink deposit becomes uneven; above 140 mesh you start blocking particles and losing sparkle. For pearlescent inks with interference effects (the colour-shift grades), we specify 100 mesh as our standard.
For offset metallic work, we use purpose-formulated paste inks with aluminium flake ground to a D90 of ≤20 µm and ink tack values of 8–12 (Inkometer at 30°C, 400 rpm) — standard process inks run 12–18 tack, and metallic pastes need to be softer to reduce roller shear. We run these on our Heidelberg XL106 sheet-fed lines with dampening pressure reduced by approximately 15% versus standard CMYK jobs, because excess water emulsification greys out metallic inks faster than almost any other variable.
Gravure is our preferred process for metallic inks on flexible packaging — the engraved cell structure deposits a consistent ink film and the doctor blade does not shear platelets the way offset rollers do. Cell depth for metallic gravure typically runs 28–38 µm, deeper than standard process gravure (18–25 µm), to accommodate the higher pigment load.
Substrate Compatibility & Surface Preparation #
Metallic and pearlescent inks are unforgiving of substrate roughness. The platelet particles need a smooth, flat surface to orient correctly — on a rough or absorbent surface, particles tilt at random angles and the specular reflection scatters, producing a dull, hazy result.
For offset metallic on folding carton, we specify cast-coated or high-gloss coated board with a Parker Print Surf (PPS) roughness value of ≤1.5 µm. Standard SBS board at PPS 2.5–3.5 µm will produce noticeably inferior metallic results. If a brand partner is committed to an uncoated or textured board for sustainability or aesthetic reasons, we recommend switching to a pearlescent effect rather than a specular metallic — the diffuse interference colour of pearlescent pigments is more forgiving of surface texture.
For screen-printed metallics on rigid box wrapping paper, we typically apply a UV flood coat base (energy cure at 120–160 mJ/cm² per ISO 2884-1) before the metallic screen pass — this seals the paper surface and dramatically improves particle orientation and adhesion. Without this base coat, we see adhesion failures in cross-hatch tape tests (ISO 2409) at rates above 15% on uncoated papers.
Ink adhesion on film substrates for flexible packaging must meet a minimum peel strength of 1.5 N/15mm (tested per ASTM F904) after 48-hour conditioning at 23°C/50% RH. For food-contact flexible packaging, all metallic and pearlescent inks we specify comply with EU Regulation 10/2011 on plastic materials in food contact and are reviewed against FDA 21 CFR 175.300 where US market compliance is required.
Specification Notes for Brand Partners #
When you brief us on a job requiring metallic or pearlescent inks, the most useful information you can give us upfront is: the substrate type and finish, the target effect (satin metallic, high-sparkle, colour-shift pearlescent), and a physical reference sample if you have one. The most common brief mistake we see is specifying “gold metallic” without clarifying whether the target is a warm yellow-gold, a pale champagne, or a rich bronze — these require completely different pigment formulations and we cannot match a reference we haven’t seen.
Our standard workflow: digital colour proof in 3–5 working days (note: metallic effects cannot be fully represented on digital proofs — we always flag this), physical drawdown or press proof in 8–12 working days, production lead time 18–25 working days after approved sample. For screen-printed metallic on rigid boxes, add 3–5 working days for screen preparation. MOQ for specialty metallic ink jobs typically starts at 1,000 units for rigid boxes and 3,000 units for folding cartons, though we review this case by case based on substrate and finishing complexity.
Frequently Asked Questions #
Q1: What particle size should I specify for a high-sparkle gold metallic on a folding carton?
A: For maximum sparkle, you need a coarse-grade aluminium flake with median particle size of 40–100 µm — but this cannot be run in offset. On our folding carton lines, we would apply this via a screen printing pass over the offset-printed base, using a 100-mesh screen. If the job must be offset-only, we cap particle size at 20–25 µm and the result will be a satin rather than high-sparkle finish.
Q2: What is your MOQ and lead time for a pearlescent ink folding carton job?
A: Our standard MOQ for folding carton jobs with specialty pearlescent inks is 3,000 units. Lead time from approved sample to production delivery is 18–25 working days. If the job requires a UV base coat pass before the pearlescent layer, we build in an additional 2 working days for the extra press pass and curing cycle.
Q3: Do your metallic inks comply with food-contact regulations for packaging used in the EU and US?
A: Yes — for any food-contact application, we specify inks that comply with EU Regulation 10/2011 on plastic materials and articles intended to contact food, and we cross-reference against FDA 21 CFR 175.300 for US market shipments. We require your brand to confirm the food-contact surface configuration (direct or indirect contact, barrier layer present or absent) before we finalise ink selection, as this affects which pigment grades are permissible.
Q4: Can pearlescent colour-shift inks be combined with CMYK offset printing in a single job?
A: Yes, and we do this regularly. The standard workflow is to run CMYK offset first, then apply the pearlescent layer as a fifth or sixth pass — either offset with fine-grade pigment (≤15 µm) or screen for coarser interference grades. Register between passes on our sheet-fed offset line holds to ±0.15 mm, which is sufficient for most overprint effects. We recommend designing the pearlescent layer as a spot colour with deliberate trapping of 0.2–0.3 mm to accommodate any inter-pass movement.
Q5: Why did our metallic ink look dull and grey after printing — what went wrong?
A: The most common cause is water emulsification in offset printing. Metallic paste inks are highly sensitive to excess dampening solution — even a 5–8% water pickup in the ink train will grey out aluminium flake pigments by disrupting platelet orientation. On our Heidelberg lines, we reduce dampening pressure by approximately 15% for metallic jobs and monitor ink train temperature to stay below 32°C. The second most common cause is substrate roughness above PPS 1.5 µm — on rough board, platelets tilt randomly and specular reflectance drops from the expected 75–88% range down to 50–60% or lower.
Planning a packaging project? Contact our team to request a complimentary specification review and sample quote.
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