Metal Decorating Inks

Metal decorating inks are printed onto tinplate, tin-free steel and aluminium by two routes. Flat sheet is printed by lithographic offset on a sheet-fed press, and the printed sheet is then made into three-piece bodies, drawn food cans, ends and closures. Two-piece beverage cans, monobloc aerosols and collapsible tubes are printed after the body has been formed, by dry offset from a blanket onto a body turning on a mandrel. In both routes the metal absorbs nothing. The ink sits on a cured size coat or basecoat, or on bare metal, is covered by a varnish, and dries only in the oven or under the lamp.

An ink on metal is judged on what happens after the press. It has to take one or more further bakes without shifting colour or losing adhesion, move with the metal through drawing, necking, beading, seaming or crimping without cracking, and come through pasteurisation, retort or a hot water bath without blushing or lifting under the varnish. It also has to leave the finishing varnish free to set the slip and scratch resistance the pack needs on the conveyor. Each Arcdeco grade is therefore specified against the coating stack, the oven schedule and the forming sequence of the customer’s line.

Arcdeco sits between two existing Arctic ranges. The Metal Packaging Coatings range, Arccan, supplies the films below and above the ink: internal linings, the size coat and white base for sheet-fed lines, the external white basecoat for two-piece bodies, and the overprint and finishing varnishes applied over the ink. Arcdeco supplies the printed colour layer only, and each grade is qualified with the Arccan or Arctube films it will run between. On aluminium tubes and monobloc aerosol cans the basecoat below the ink and the overvarnish above it come from the Arctube range. The Printing Inks page on this site covers gravure and flexographic inks for flexible packaging, paper and board: liquid inks dried by evaporation or cured by UV, and never stoved. Thermochromic and fluorescent coatings for paper, board and film are in the Arcveil range.

External decoration does not touch the food, but it is part of a food-contact article. The metal is an absolute barrier, so the routes that matter are set-off from the printed face onto the internal lacquer of the next sheet in the stack, contact at the rim and neck of a drinking can, and substances left by incomplete cure. Compliance is established for the finished pack against the law of the market of sale: in the European Union Regulation (EC) 1935/2004, Regulation (EC) 2023/2006 on good manufacturing practice, which addresses set-off from inks on the non-food side, and Regulation (EU) 2024/3190, which prohibits bisphenol A and other hazardous bisphenols in printing inks as well as in coatings; in India the Food Safety and Standards (Packaging) Regulations, 2018. Arcdeco grades are formulated without PTFE wax. Raw material exclusions required by the brand owner are taken at enquiry, and a declaration is issued on request with the Technical Data Sheet. No approval, certification or accreditation is claimed for these products.

Thermally cured lithographic inks for tinplate, tin-free steel and aluminium sheet, printed over a cured size coat or white base and stoved in a wicket oven under a finishing varnish applied wet or on a separate pass. Grades rise in flexibility from food and general line bodies to closure stock and drawn and redrawn cans.

Free-radical UV-curing lithographic inks for metal sheet, cured between units or at the end of the press so the sheet can be stacked or varnished without an ink oven pass. Specified for adhesion through the thermal bakes that may follow and for full cure against set-off in the stack.

Thermally cured inks for the can decorator, laid side by side on a common blanket and transferred to the can in one revolution, then overvarnished wet and cured through the pin oven and the internal bake oven. Specified for transfer at line speed, heat history, necking and mobility.

Concentrated oil-based dry-offset inks for impact-extruded aluminium monobloc aerosol cans and collapsible tubes, printed over a base enamel and varnished wet. Specified for the necking of the aerosol shoulder or the folding and squeezing of the tube.

Dry-offset effect inks run at a decorator station alongside the standard set: a reversible cold-activated thermochromic ink and a matt and gloss contrast ink. Each effect is qualified on cans that have seen the full heat history of the line.

The figures below are the typical operating window for this range, not a measured result for any one batch. Confirmed values are issued with the Technical Data Sheet and Certificate of Analysis by our laboratory.

The sheet-fed line

On a sheet-fed metal decorating line the sequence is set by the oven. The sheet is roller coated with a size coat or white base, typically Arccan SF 120, and stoved in a wicket oven before it reaches the press, with whites often applied in two coats for opacity. The press is lithographic with dampening, so the ink has to hold its ink and water balance on a surface that absorbs nothing, and on a multicolour press each colour traps wet onto the one before, which needs tack graded down the sequence. The finishing varnish is then roller coated either wet over the ink on a tandem line, stoving with it, or on a separate pass over the stoved ink, as with Arccan SF 230; each stoving is typically 10 to 12 min at 150 to 205 degrees C peak metal temperature. The ink must not bleed into the varnish solvent.

Every further pass is another bake for the ink already on the sheet: a second print pass on a two-colour press or an internal lacquer stoved after decoration. Colour and adhesion are checked after the full number of bakes the sheet will see, and pigments are chosen for it. Diarylide yellows, for example, are not used where the ink sees stoving above 200 degrees C, because they can break down at that temperature. The cured sheet is then welded, beaded, flanged and seamed, or stamped into ends and closures, and the ink has to follow each step.

UV and LED-UV on sheet

UV inks cure under the lamp, so the ink oven pass disappears and the sheet can be varnished or stacked at once. Over a thermal varnish the UV ink has to keep its adhesion and colour through the wicket oven and any later bake. UV films shrink as they cure and key less readily to a hard, fully cured basecoat, so adhesion depends on the surface of the size or white below, and forming severity is limited. A short dose leaves uncured material that can set off onto the internal lacquer on the back of the next sheet in the stack, which is why cure is confirmed by radiometer, solvent rub and tape, not by touch. LED-UV grades need the wavelength they were formulated for, and UV presses need EPDM or mixed-mode rollers and blankets.

The two-piece can decorator

The washed body, white basecoated where the design needs it, is decorated on a mandrel. Each of the six to eight inking stations, nine on some current machines, carries a relief plate that lays its colour onto a common blanket segment, and the blanket transfers the whole design to the can in one revolution. Because the colours meet on the blanket before they reach the can, they cannot be trapped wet one over another as on a sheet-fed press: where two images overlap, the following plate lifts wet ink back off the blanket into its own inking train. Designs are built from solid colours fitted side by side, tints made with halftone screens, and a limited, agreed overlap of dots for process work.

The overprint varnish goes on wet immediately after the decorator, and the bottom rim coat is applied at the decorator or a separate rim coater. Ink and varnish are set in a short pin-oven dwell and their cure is completed in the internal bake oven after the inside spray, so the decoration always sees at least two bakes before necking, filling, seaming and pasteurisation. Mobility and scratch resistance on the conveyor come mainly from the overprint varnish and rim coat; the ink must not disturb them, because excess wax makes the varnish crawl and a soft ink marks under line pressure.

Monobloc aerosols and collapsible tubes

Both are impact extruded from an aluminium slug, the tube annealed soft before lacquering, then lacquered inside, base enamelled outside and printed by dry offset, with the varnish usually applied wet. The aerosol is then necked and shaped through a long series of dies, which deforms the ink on the shoulder more than anywhere else, and the filled can passes a hot water bath. The tube is filled, folded and crimped, and squeezed by the user, so its flexibility has to last for the life of the tube.

Effect inks

Arcdeco FX grades run at a free decorator station and are judged on cans that have come through the pin oven, the internal bake oven and pasteurisation. The thermochromic capsules have a heat limit, so the bake schedule is agreed before the trial. The matt and gloss contrast ink is qualified with its named varnish. Fluorescent, pearlescent and textured effects are assessed on request against the same heat history, and no effect is offered on the strength of a flat drawdown.

Colour matching and approval

Colour is matched on the customer’s own white base, size or bare metal, at the film weight the process lays down. A laboratory proof is the starting point, not the approval, because a decorator blanket and a sheet-fed press lay different films and colour moves in the oven. Approval is taken from production sheets or cans after the full bake sequence, measured to ISO 13655 and compared by CIEDE2000 against a signed standard. ISO 2846-1 defines process colour on a reference paper and is not carried over to metal, and bare-metal grounds are read with a geometry agreed with the customer.

Handling and storage

Keep containers closed, within the storage temperature on the Technical Data Sheet and away from heat and direct sunlight, and bring ink to pressroom temperature before use, because tack and viscosity move with temperature. Oxidatively drying grades may skin in an opened container, so the surface is covered between uses. UV and LED-UV grades are kept in opaque containers away from daylight and are not mixed with conventional inks or wash-up. Handling precautions are given in the Safety Data Sheet, available on request.

Specifying a metal decorating ink needs the coating stack, the line and everything that happens to the metal after the press. The following are the questions Arctic will ask, and the answers usually come from the printer or can-maker and the brand owner together.

Substrate and coating stack

• Tinplate with its tin coating weight, tin-free steel, or aluminium with its alloy and temper, and the gauge.
• Which size coat, white base or basecoat the ink is printed on, from whom and at what cure schedule, or whether it is printed on bare metal.
• Which finishing or overprint varnish goes over the ink, whether it is applied wet or on a separate pass, and whether it is thermal, UV or LED-UV.
• Whether the internal lacquer is stoved before or after decoration.

Line and oven

• Sheet-fed press, can decorator, monobloc printer or tube printer, with the number of units or stations and the line speed.
• Wicket oven, pin oven, internal bake oven or drying oven schedules as peak metal temperature and dwell, and how many bakes the ink sees in total.
• For UV lines, the lamp type or LED wavelength, the number and position of curing stations, and the roller and blanket compounds.
• The dampening system and fountain solution on sheet-fed presses.

Colours and standards

• Spot colours, a process set or both, and how the standard is held: physical sample, reference number or digital standard.
• The approved tolerance and the measurement geometry, particularly on metallic or bare-metal grounds.
• For dry offset, the screen ruling and the dot overlap the design depends on.
• Any effect wanted, and the station and varnish available for it.

Forming and sterilisation

• What the printed metal becomes: welded body, drawn and redrawn can, end, crown, lug cap, necked beverage can, shaped aerosol or tube.
• The forming severity: draw ratio, necking and shaping stages, bead depth, fold and crimp geometry.
• Any heat after printing to gel or mould a sealing compound.
• Pasteurisation or retort time and temperature, the hot water bath for aerosols, and the conveyor and case-packing route the pack travels.

End use and regulatory

• The pack contents and the market of sale, and so the food-contact legislation the finished pack is assessed against.
• Any raw materials the brand owner excludes, such as bisphenol A, PFAS or named photoinitiators, and from what date.
• Whether the printed face will lie against the food-contact side of another sheet or part in the stack, and for how long.
• Which documents are needed in the dossier, and who signs the declaration of compliance for the finished pack.

The Technical Data Sheet, Safety Data Sheet and regulatory declaration for any grade in this range are issued by our laboratory against the substrate and process you are running. Tell us the job and we will specify against it.