In the digital world the ink represents a key part of the technology within the total system. With screen-printing ink, it is available as a liquid in a can and is only dependent on the criteria required for analogue production. But all ink has to be able to do what it says on the tin when providing the final, viewable image, and it needs to offer consistent output without fading, smearing or chipping off.

Printer manufacturers regularly get criticised for the cost per litre of ink. The smaller the output device, the more expensive this becomes with desktop ink-jet printers suffering the most when it comes to assessing the cost of each colour cartridge.

Digital ink-jet ink represents a key part of the total printing machine's engineering

Compared with its analogue counterparts, digital ink is expensive to develop and to manufacture, and its packaging doesn't come cheap, either. Using any of today's formulations isn't merely a question of opening a tin, stirring the contents, and pushing it through a screen. In digital use, ink has a far more convoluted role to play. It has to be compatible with all the elements of the printing machine, needs to behave itself when being jetted and must dry quickly and efficiently. Not only that, it should behave on the finished material not only in terms of the colour and end quality of the print but, also, in terms of adhesion and durability.

As such, ink in a wide-format printer is part of the overall machine's design and build, and not just a liquid which has come along as an afterthought. In fact, it's worth considering that it is the ink which is the key to the platform, with its chemistry playing a cogent role into the development of the printer itself. Ink-jet ink also has to be compatible with the print-heads, and be able to jet efficiently across a range of different temperatures and levels of humidity.

No ink is merely a fluid with a bit of colourant added. For digital devices, the precision accountability of its behaviour is crucial because of the complexity of the elements in an ink-jet printer. Perfecting its chemistry and ongoing performance is also subject to continual improvements and enhancements, and all ongoing developments take time and cost money. And, as formulations change, so research continues.

So it's hardly surprising that digital ink costs more than its analogue counterparts, whether it's supplied in tidy cartridges or in a container where supplies can be refilled on the fly. Every print that's output is the result of considerable research and development, and that's no mean feat considering all the criteria expected in today's ink-jet formulations.