Putting Ink on Board: The science that makes it stick

In our last instalment, Material Matters, we picked the board. Now comes the fun bit: getting your design onto it. If you've ever wondered why one carton's colours look so crisp while another's look a bit tired, the answer is usually the print process and how carefully the colour is managed.

Printing methods and their use cases

There are three main methods of printing on packaging:

• Lithographic (offset) - The workhorse. Ink is transferred from metal plates to board, giving sharp detail and consistent quality. Best suited to medium and large runs.

• Digital - The flex option. Artwork is printed straight from the file, with no plates at all. Ideal for short runs, prototypes and lots of versions.

• Flexographic (flexo) - The no-frills solution. Flexible relief plates on rotating cylinders print with fast-drying inks. Widely used for corrugated outer cases, labels and flexible packaging, it's quick for long runs of simpler graphics, though it doesn't usually match litho for fine detail.

  
  

At Quantum we print cartons either on lithographically or digitally. Each is good at different jobs, and picking the right one is mostly about how many cartons you need. Here's a closer look at how each one works and when you'd use it.

Litho printing - The workhorse

Litho (short for lithographic, and also called offset) printing has been the backbone of carton printing for decades, and for good reason.

Your artwork is split into its separate colours, and each colour gets its own metal printing

plate. The plate picks up ink and passes ("offsets") it onto a rubber blanket, which then presses it onto the board. Most full-colour images are built from four process inks, cyan, magenta, yellow and black (CMYK for short), laid down as tiny dots that your eye blends into a full picture.

Litho really shines when you are looking at

• Big runs. Once the plates are made and the press is set up, each extra sheet costs very little. The more cartons you print, the better value each one becomes.

• Consistency. Litho delivers the same result sheet after sheet, which matters when you're printing tens of thousands of cartons.

• Detail. Fine text, small barcodes and delicate gradients come out beautifully sharp.

• Spot colours. Alongside CMYK, we can print specially mixed inks (often matched to the Pantone colour system) when a brand colour has to be spot on, or is simply too vivid to build from four inks.

  
  

The trade-off is set-up. Making plates and getting the press running takes time and material, so litho isn't the cheapest option for a small quantity.

Digital printing - The flex option

Digital printing skips the plates entirely. The press takes your artwork straight from the file and prints it, a bit like a very clever, very large office printer.

Because there's so little set-up, digital is brilliant for:

• Short runs. A few hundred cartons for a product launch, trial or seasonal special.

• Fast turnaround. No plates to make means you can go from approved artwork to printed sheets quickly.

• Prototypes and samples. Seeing (and holding) a real printed carton before committing to a full run is hugely useful.

• Versioning. Every carton in a run can be slightly different, so you can print different flavours, languages or even personalised names in one go.

  
  

Digital has come on enormously in recent years, and the quality gap with litho is much smaller than it used to be. For very large quantities, though, litho still usually wins on cost per carton.

Digital printing - The flex option

Flexo (short for flexographic) printing is the go-to for the brown corrugated boxes your online orders arrive in.

Instead of flat metal plates, flexo uses flexible rubber-like plates with the image raised slightly from the surface, a bit like a very sophisticated rubber stamp. The plates are wrapped around rotating cylinders, and a finely engraved roller (called an anilox) feeds them a precise, thin layer of fast-drying ink, which is then pressed straight onto the material. Most flexo presses print from a continuous reel rather than individual sheets, which is a big part of why they're so quick.

Flexo comes into its own for:

• Very long runs. Once it's up and running, a flexo press is extremely fast, so it's hard to beat for huge quantities.

• Tricky materials. It prints happily onto plastic films, foils and the rougher surface of corrugated board, which other methods can struggle with.

• Simpler graphics. Bold colours, logos and text, such as the branding and handling marks on a shipping case, are exactly what flexo does best.

  
  

The trade-off is detail. It doesn't usually match litho for fine text, small barcodes, photographic images or smooth gradients. That's why, for the printed cartons our customers put on the shelf, where the quality of the print is doing the selling, we use litho and digital instead.

Colour management: making your blue, your blue

This is my favourite bit, and it's the part most people never think about.

Colour is surprisingly slippery. The screen you designed on creates colour with light (RGB), while a press builds it from ink on board (CMYK), so something that looks punchy on a monitor can come out quite differently in print. The board plays its part too. Ink on a bright white coated surface looks crisper than the same ink on a natural or recycled board. So does the ink: we print with vegetable-based inks as standard, but can switch to food-grade inks where a carton needs them, and mix customer-specific colours (if your design uses spot colours, we can arrange a drawdown / sample).

Colour management is how we take all of that slipperiness and pin it down, so your colours come out right and stay right.

It starts before we go anywhere near the press, taking your artwork and ensuring it is ready for printing - for example, adding bleed (a little extra artwork beyond the cut line, so there are no white slivers at the edges), and checking that your images are of high enough quality to print sharply.

We then move to press. At 'make-ready', we build up the strength of each colour until it matches your target, usually a Pantone reference or an approved printed sample. This is also where we love having customers on site for a press pass. There's nothing quite like seeing your own cartons coming off the press, and it means you can sign off the colour with complete confidence before the run goes ahead.

Once we're running, the job is to hold that colour steady from the first sheet to the last. The press carries out its own automated checks as it goes, and our trained printers back these up with hands-on checks throughout the run. Machines are brilliant at consistency, and experienced eyes are brilliant at spotting the things machines don't; we use both.

Finally, we think about next time. We keep a record of previous versions and press settings, so when you reorder next year, the new batch matches this one.

The result? The blue on your carton is your blue, on every box, in every batch, whenever it was printed.

Coatings and varnishes: sealing it in

Once the ink is on the board, the final step in the print process is usually to seal it in with a coating or varnish. It's easy to think of this as a finishing touch, but it's doing two important jobs at once.

The first is protection. Between our press and the shelf, your cartons get packed, shipped, stacked and handled more times than you'd probably like to know. A coating guards the print against scuffs, scratches and moisture along the way, so your cartons still look their best when a customer finally picks one up.

The second is look and feel. The coating you choose changes how a carton looks on the

shelf and how it feels in the hand. A gloss finish gives a shiny, eye-catching surface that really makes colours pop. A matt finish feels softer and more understated, often with a premium edge. Silk sits comfortably in between.

That's exactly why it pays to think about your finish early on, rather than leaving it as an afterthought. The coating affects how your colours come across, so the same blue can look rich and vivid under gloss and noticeably more muted under matt. Decide on the finish at the design stage, and we can make sure the colour you approve is the colour you get.

Up next

With the ink on the board and sealed in, it's time to make it sparkle. Next in the series we'll dive into the art of finishing: foiling, embossing, spot UV and those lovely soft-touch coatings.

Got a packaging puzzle of your own? The team at Quantum Print & Packaging would love to hear about it.