What Is White Ink Printing? How White Becomes Visible on Clear Stickers

The glass door of the workshop is tinted dark, and the logo has white lettering. The clear sticker arrives and goes on. You can hardly see the lettering at all. The printer printed exactly what was in the file. There just wasn't any white in it.

What is white ink printing? In white ink printing, an opaque white ink is printed so that white becomes visible at all on see-through or non-white materials. On clear stickers, this one colour decides whether a logo stands out on glass or dark plastic, or disappears into the surface behind it.

What is white ink printing, and why does colour printing have no white?

Standard colour printing works with four process colours: cyan, magenta, yellow and black, CMYK for short. White is not one of them. On paper or white film it isn't missing either, because there white simply appears wherever the material is left unprinted.

On top of that, printing inks have a particular property. They are translucent, meaning light shines through them, and they need a light background to look right. White film provides that background; clear film does not.

White is printed as a colour of its own, because it cannot be mixed from the four process colours.

At print shops you will often hear the term "opaque white". It means the opaque white ink that acts as a base coat and replaces the white material. In everyday use, print shops mean largely the same thing by opaque white and white ink printing.

Clear stickers without white: what happens then

If you have clear stickers printed without white ink, all the white areas in the design stay see-through. Where there was white on screen, you will later see the glass door, the casing or the packaging behind it.

The other colours change too. On clear film against a light background they look pale and lack contrast. On a dark or coloured surface they turn darker and distorted, because the translucent ink lets the surface show through. A colourful logo on an anthracite machine casing then looks much duller than in the file.

Our advice: before you order, go through every white element one by one. Should there be white here later, or should the surface show through? The answer is often mixed: the lettering should be white, the area around it can stay clear.

How white ink printing works: underprint, spot, full coverage

Which option fits depends on where the sticker goes and from which side it will be seen.

White underprint beneath the colour

With an underprint, white goes onto the film first and the colour on top of it. The white takes on the role of white paper. That way the design looks strong even on dark, coloured or see-through material, as long as you look at it from the printed side. This suits stickers you look at directly: on the outside of a window or on a toolbox.

Spot or full-coverage white

White does not have to cover the whole area. With spot or selective white, it sits only under certain parts of the design. The logo then stands on white, and the film around it stays clear. With full-coverage white, the entire design is backed with white.

White as a colour in its own right in the design

White can also be the design itself, for example as white lettering on clear film or as a white accent on coloured material.

White over the colour, for viewing through the glass

If a sticker goes on the inside of a window and is to be read from outside, the order is reversed. The design is printed mirror-reversed and then overprinted with white. You still supply your file the right way round and state that it will be applied on the inside; we do the mirroring. From outside, looking through the glass, you see the colour first, with the white behind it. The film and adhesive must be optically clear for this. Behind tinted glass, the design looks darker from outside. If there is already a tinting film on the inside, clarify that with us first.

For lettering that needs to work both in daylight and when backlit, there is a third build: colour, white, colour. The white then sits between two layers of colour.

Printing methods: what white is printed with

White can be printed using several methods: screen printing, digital printing, offset printing (usually with UV curing there), flexographic printing and pad printing. For digital white printing, there is white ink for UV, latex and eco-solvent printers.

In digital printing, white ink takes more effort than the other colours. Its pigments settle, so it is kept constantly circulating in the machine.

UV printing can do more. There the ink cures instantly, and white and varnish can be printed on top of each other so many times that a texture you can feel builds up, all the way to tactile elements.

Opacity and the limits of printed white

How opaque white turns out depends on the printing method, the amount of ink and the material. For more opacity, white is printed in several layers or with more ink laid down. Test prints before production are common.

One printer manufacturer gives a figure for its white latex ink: 91 % visual opacity, according to its own test (as of 2020), as an underprint with 160 % ink density on black adhesive film. The figure only applies under exactly these conditions. So printed white is not always fully opaque.

The second limit is registration. Some digital printers apply white and colour in a single pass, and then the offset between the layers is usually very small. If printing is done in several passes, for example with drying time in between, white and colour can shift slightly against each other. A thin white fringe then peeks out at the edge. In the print shop, a flaw like this is known as a "halo". What helps is setting up the white area in the print file very slightly smaller than the colour design.

Stickers with white ink: when it is worth it

Typical uses for white ink printing are clear films and labels, glass, dark or coloured surfaces, kraft paper, natural board, metallic material and packaging.

• Glass doors and shop windows: logo, lettering or opening hours on clear film. Without white, light-coloured lettering stays see-through; with white, it stands out visibly on the glass.
• Dark casings and toolboxes: a coloured logo with a white underprint stays strong instead of sinking into the dark plastic.
• No-label-look labels: clear labels are printed so that it looks as though the packaging has been printed directly. For this, coloured parts of the design are backed with white in a targeted way.
• Kraft paper: the natural brown paper distorts the printing inks. For light and bright colours, white goes underneath.
• Metallic film: where there is white, the shine disappears. Where there is none, the metallic effect stays visible. This lets you place shiny areas in the design deliberately.

Not every sticker needs white ink. If nothing of the surface should show through anyway, there is also the white sticker. There the material provides the white, and only the four colours are printed. Single-colour lettering can also be cut from vinyl, with no printing at all. When foil technology makes sense and when digital printing does is covered in Foil technology or digital print?

White in the print file: the principle

Because white is a separate colour, it needs its own instruction in the print file. White is set up as a spot colour on its own layer, separate from the colours. Whether the white goes under or over the colour depends on which side the sticker is viewed from.

What the spot colour has to be called is set by each print shop or its software. Ask us for the name and for how the white layer should be set up before you create the file.

In our free file check, we look over your file before printing. We are happy to clarify with you in advance whether and where your design needs white. Tell us what the sticker is going on and whether it goes inside or outside.

A typical case: the white logo on the tinted workshop door

A trade business wants its logo on the dark-tinted glass door of its workshop and on its toolboxes. The lettering in the logo is white, the symbol next to it coloured. The file arrives as a normal colour image, with no information about white. So before printing we ask: where should the white go, and is the door sticker going on the inside or the outside?

Printed as a clear sticker without white, the lettering would be see-through. On the door, you would only see dark glass in its place; on the toolbox, the black plastic. The coloured symbol would look duller than planned.

The right answer here is spot white: the lettering is printed in white, the coloured symbol gets a white underprint, and the area around it stays clear. For the toolboxes this underprint is enough, because they are seen from the printed side. For the door too, given this dark tint, we recommend applying it on the outside with an underprint, because behind tinted glass the design looks darker from outside.

What the screen doesn't tell you about white

On a clear sticker, white is a colour you have to plan for specifically. On screen, a logo with white lettering looks finished, because the monitor shows white as a solid colour. In colour printing, though, white is a spot with no ink, and on clear film it stays see-through. If you decide before printing where the white should go, or show us the file in our free file check, you will usually get the sticker exactly as intended the first time.

How a sticker in a shop window stands out overall is shown in our article Stickers you can't overlook. Shop window lettering and window films are under Foil technology.

Conclusion: white ink belongs in the order

White ink is a separate, opaque colour. Without it, white areas on clear stickers stay see-through, and colours look dull on a dark surface. Before you order, clarify:

• Where should the white go? Under the whole design, only under certain parts, or as white lettering?
• From which side will it be seen? Applied on the outside, white goes under the colour. On the inside behind the glass, it goes over it, and the design is printed mirror-reversed.
• How dark is the surface? Printed white covers differently depending on the method and material. For very dark surfaces, a test print is worth it.

Not sure whether your design needs white? Write to us via Contact and tell us what the sticker is going on. Order stickers online at koeck-print.at. Whether inside application or colour-white-colour is possible for your design, we clarify through the contact form.

Frequently asked questions

What is white ink printing?

In white ink printing, an opaque white ink is printed; print shops often call it "opaque white". Normal colour printing with cyan, magenta, yellow and black has no white; there the white material is simply left unprinted. On clear film, glass, kraft paper or dark material, that white does not exist. There it has to be printed specifically.

Is white printed automatically on a clear sticker?

You should not rely on it. White is a separate colour and is set up on its own layer in the print file. If this information is missing, white parts of the design stay see-through on clear film. Before you order, clarify where the white should go and whether the sticker goes on the inside or the outside.

How opaque is printed white?

That depends on the method, the amount of ink and the material; white printed in several layers covers more. One printer manufacturer gives 91 % visual opacity for its white latex ink, according to its own test (as of 2020), as an underprint with 160 % ink density on black adhesive film. For a very dark surface, a test print is worth it.