UV printing on metal: aluminium, stainless steel and metal posters
are explained briefly when you hover over or tap them.
Metal is one of the most popular materials in UV printing: signs, business cards, name plates, bottle openers and photos on aluminium. At the same time, bare metal is one of the substrates on which UV ink holds worst without preparation. The difference almost always lies in the surface.
Which metal, which surface?
What counts for printing is not the metal itself but what is on top of it.
| Surface | Primer | Typical use |
|---|---|---|
| Coated aluminium (white, silver, gold) | usually no | photo prints, signs, business cards |
| Sublimation and photo metal | usually no | metal posters, photo prints |
| Anodised aluminium | usually yes, test it | name plates, business cards, tools |
| Bare or brushed aluminium | yes | industrial parts, decoration |
| Stainless steel | yes | bottles, cups, signs |
| Powder-coated metal | often yes | cups, housings |
Coated plates are the easiest choice for getting started. Their surface is made for printing. Bare aluminium and stainless steel are harder, because the ink finds hardly any grip on the smooth, dense surface.
Preparation: degreasing
Metal is almost never truly clean. Machining oil, corrosion protection and fingerprints sit invisibly on the surface.
- Put on gloves and from now on do not touch the print surface with bare fingers.
- Wipe in one direction with isopropanol and a lint-free cloth.
- For stubborn grease, wipe a second time with a fresh cloth.
- Let it dry completely.
For protective films on plates: only peel off the film directly before printing.
Primer or not?
On bare metal and stainless steel you need primer. Manufacturers offer dedicated metal primers or combined glass and metal primers for this. Apply thinly, let it flash off, print promptly. The details are in the article on primer.
For anodised aluminium it is worth running a test without primer. Some anodised layers accept ink well, others do not. On coated plates, primer is usually unnecessary and can even interfere.
After printing, do a tape test on an offcut. Only when that holds do you print the series.
With white or without?
This is where you decide the look.
With a white underprint you get bright, opaque colours. The metal disappears beneath the design. That is right for logos in corporate colours, photos with skin tones and anything where colours must be exact.
Without white, the metal shows through the colour. Colours look darker but they shine metallically. A blue becomes a shimmering metallic blue. That is a nice effect for decoration, jewellery pendants or photos with a lot of sky and water.
The two can be combined: white only where colours should glow, bare metal where it may shine. You set this up in the file with a separate white layer. How to do that is explained in Ink layers.
A note on very shiny surfaces: mirror-polished metal reflects UV light back to the print head. In the worst case this can cure ink on the nozzles. Some devices are designed for this; on others a slightly larger gap helps. Check the manufacturer’s specifications.
Durability and scratch resistance
Well-adhering UV ink on metal tolerates handling, wiping and everyday indoor use well. The critical points are:
- Edges and corners, where ink comes off first
- Parts that rub against other metal, such as key fobs on a key ring
- Dishwashers and aggressive cleaners
- Outdoor use over years
A full-surface coat of varnish protects the colour from scratches. After curing, also give the print some time before you package or stress it. Many manufacturers state at least 30 minutes, and full adhesion builds up over hours in some cases.
Metal posters and photo prints on aluminium
Photos on aluminium are a classic product. Usually white or silver coated aluminium plates are used. White coated gives classic photo colours, silver the typical metallic look.
A few points decide the quality:
- Resolution: Photos should have about 150 to 300 dpi at final size. Small phone pictures quickly turn soft at A3.
- Colour profile: Skin tones on metal are sensitive. A suitable profile for material and ink makes a big difference.
- Varnish: Gloss varnish makes photos look deeper and protects when cleaning.
For business use
With metal posters, complaints are often decided not by the print but by everything around it.
- Back: The adhesive strip, hanger or standoff frame must suit the weight. Cheap adhesive pads come loose on large plates.
- Hanging: Tell your customers clearly which hanging system is included and what they need themselves.
- Edges: Deburr sharp cut edges or use rounded corners.
- Packaging: Protective film or tissue paper on the print side, edge protection, stiff cardboard. Metal bends more easily in shipping than you might think, and a dent ruins the picture.
Calculate plate, primer, white, varnish, hanging system and packaging together. How is explained in the UV costing guide.
Continue with: Primer, Varnish and the materials overview.