Technologies
Special Effects
Drip-off, raised crystal, haptic sand, soft touch, foil and colour-change — what each effect physically is, and what the press has to do to get it.
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The technology
Special Effects
An effect is a surface, and a surface is made by controlling three things: how much material is laid down, where it flows before it sets, and when it is locked. Almost every decorative effect in packaging is a variation on those three, and the ones that fail on press usually fail because one of them was left to chance.
Some effects are contrast effects: matt against gloss, smooth against textured, cold against warm to the hand. Some are structure effects, where a heavy film is deliberately allowed to break into a texture before it is cured. Some are optical, where a pigment or a foil redirects light. And some are responsive, where the surface changes with temperature or light. They demand different things from the press and they have very different costs.
We match and supply effects to a physical sample, because an effect cannot be specified by a colour number. Send the sample and the substrate, tell us the press and the cure system, and we will tell you what is reproducible at your speed and what is a hand-proof that will not survive a production run.
How it works
How the main effects are actually made
- Drip-off (matt/gloss differential). A matt or oleophilic primer is printed where the matt is wanted, then a UV gloss coating floods the whole sheet. The gloss coating de-wets where the primer sits and pulls back into a gloss film everywhere else. The contrast is produced by surface tension, not by registration of two coatings, so the register tolerance is generous and the visual effect is sharp.
- Raised crystal and structure. A heavy UV coating — typically screen-applied — is partly gelled under a low-power lamp so that the surface breaks into a controlled texture, then fully cured. The texture scale is set by the gel step, not by the coating alone: same coating, different first lamp, different crystal.
- Haptic sand and soft touch. A matting agent or a microsphere filler at a controlled loading gives a surface that reads as sand or as suede to the hand. Soft touch is a resin property; sand is a filler property; the two are often combined.
- Cold foil and metallics. A UV adhesive is printed where the foil is wanted and the foil is nipped onto it in line, or a metallic-pigmented ink is laid as a solid. Cold foil gives a mirror; metallic ink gives a metal-like solid with a coarser reflection and far lower cost.
- Thermochromic and photochromic. Encapsulated leuco dye systems that change with temperature or with UV exposure. Fully reversible or one-shot, with a stated activation point, and with light fastness that is low by nature.
On the press
What an effect costs you on the press
Effects are heavier films than normal print, and every consequence follows from that. A raised or textured coating at 30 to 80 g/m² needs the dose and the penetrating wavelength to cure at depth, so a gallium-doped lamp or a 405 nm array is usually part of the specification rather than an option. A heavy film also shrinks more as it cures, which puts stress on the interface: adhesion and crease performance are checked on the finished construction, not on a coupon.
Downstream matters as much. A soft-touch or haptic surface changes the coefficient of friction, so packing lines, folder-gluers and cartoning equipment behave differently — we state the surface’s slip characteristic because a beautiful carton that will not run through a gluer has failed. Where a pack is glued, the effect coating must be kept out of the glue lap, and where it is foiled, the foil and the coating have to be compatible in that order.
Process window
| Drip-off | Matt primer at 1.5–3.0 g/m² from the offset or flexo deck, UV gloss flood at 4–8 g/m² in the coater. Gloss differential of 60 to 80 gloss units at 60° (ISO 2813) between the matt and gloss areas is typical and is the number to specify, rather than “high contrast”. |
|---|---|
| Raised and structure coatings | Screen-applied at 30–80 g/m² depending on the relief wanted. A low-power gel lamp sets the texture, followed by full cure; the gel lamp’s power and the time to full cure are the variables that set the crystal size, and both are recorded as part of the job specification. |
| Haptic and soft touch | 2–6 g/m² UV or aqueous. Specified by feel against a physical sample and by measured coefficient of friction to ASTM D1894, because the line behaviour downstream depends on the COF and not on the description. |
| Gloss and matt measurement | 60° gloss to ISO 2813 on the printed and coated surface; 85° for very matt surfaces where the 60° reading loses resolution. Quoted as a range on the substrate concerned, because substrate absorbency changes the result more than coating chemistry does. |
| Cure for heavy films | Heavy effect films need penetrating wavelengths: an iron- or gallium-doped mercury lamp, or a 405 nm LED array. Dose is specified per product and is higher than for a normal coating — typically 200–400 mJ/cm² for structure coatings — and cure at depth is confirmed by solvent rub and by cross-section, not by surface feel. |
| Cold foil | UV adhesive at 1.5–3.0 g/m², foil nipped in line, then overprinted or over-coated where the design requires. Adhesive, foil release layer and any overprint coating are qualified as a set; a foil that lifts is almost always a mismatch between the adhesive and the foil release, not an adhesive fault. |
| Metallic and pearlescent inks | Aluminium or mica-based pigments. Both are platelet pigments, so shade and brilliance depend on orientation in the film and therefore on film weight, anilox and press speed. Matched to a physical sample at a stated viewing geometry; a spectrophotometer number alone does not describe them. |
| Thermochromic and photochromic | Encapsulated systems with a stated activation temperature or UV response, supplied reversible or one-shot. Light fastness is low by nature — typically BWS 2–4 — and heat above the activation point during converting will show the effect prematurely, so drying and lamination conditions are set with the activation point in mind. |
| Adhesion and creasing | Heavy films shrink more on cure. Cross-cut adhesion to ISO 2409 24 h after the run, and a crease test on the actual board and grain direction. Where an effect crosses a crease or a glue lap, that is designed for at artwork stage rather than corrected at the press. |
| Downstream compatibility | Coefficient of friction (ASTM D1894) for folder-gluer and packing-line behaviour; glue-lap keep-out where the pack is glued; and a check that the effect surface takes any later coding, labelling or over-lamination it will meet. These are specified before the job runs, not diagnosed after it. |
| Specification and sampling | Effects are agreed against a physical sample on the production substrate, with gloss, COF and relief stated. We produce a press-condition sample rather than a hand proof, because a hand-drawn effect at laboratory speed is not evidence that the effect is reproducible at 150 m/min. |
Where it is used
Products and papers that build on this technology.
Specialty and Effect Inks
The effect ink and coating range.
UV Speciality Coatings
Textured, haptic and structure coatings.
From Mirror Gloss to Sand Touch
The surface science, at length.
Colour Matching
Matching metallics, pearls and fluorescents.
Fault finding
What goes wrong with effect work, and where to look.
The drip-off contrast is weak or patchy
The de-wetting is a surface-tension effect, so the primer coverage and the gloss coating’s surface tension have to stay in the intended relationship. Check primer film weight first, then coating viscosity and temperature. Patchiness across the sheet usually points to the coater rather than to either material — blanket condition, chamber pressure or anilox wear.
The structure coating cures on top and stays soft underneath
The classic heavy-film cure failure. The top of the film screens the bottom, so more dose at the same wavelength will not fix it. Move to an iron- or gallium-doped lamp or a 405 nm array for that unit, and confirm by sectioning a sample rather than by rubbing the surface.
Soft touch scuffs or marks in transit
A soft surface is a soft surface: it will mark more readily than a hard gloss, and above a certain softness that is inherent. Choose a grade balanced for scuff rather than for maximum hand feel, add a scuff-resistant overprint where the design tolerates it, and check the packing and transit conditions before changing the coating.
Cartons jam in the folder-gluer after an effect coating
Coefficient of friction. Measure it (ASTM D1894) on the coated surface rather than inferring it from feel, and keep the effect coating out of the glue lap. Many effect surfaces are either far more slippery or far grippier than plain board, and the gluer is set for plain board.
Cold foil lifts at the edges
Adhesive and foil release mismatch, or adhesive cure. Confirm the adhesive is fully cured before the nip, check the adhesive film weight, then test the same adhesive with an alternative foil. Qualify adhesive, foil and any overprint coating as a set — changing the foil supplier is a change to the whole system.
The thermochromic effect has triggered before the pack is filled
Heat somewhere in converting: a dryer, a lamination nip, a hot store. Map the temperature the reel sees against the activation point, and if converting genuinely cannot stay below it, the system has to be specified with a higher activation temperature rather than protected by procedure.
Key points
Contrast effects
Drip-off matt against gloss, specified as a measured gloss differential.
Structure
Raised crystal and haptic sand, with the gel step recorded as part of the job.
Feel
Soft touch and sand, specified by sample and by measured coefficient of friction.
Optical and responsive
Cold foil, metallic and pearlescent, thermochromic and photochromic.
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