RGB printing – and it works!

We all know that RGB cannot be printed. This colour space is intended for screens and other self-illuminating systems. For printing, we use CMYK – that’s just the way the world works. But is that still true? What if an artist and printer calledLorenz Boegli were to develop a way to print in RGB? Because that’s exactly what he’s done! And the result is a fantastic and innovative new printing technology.

RGB vs. CMYK

Until now, it has not been possible to reproduce the rich and vibrant RGB colour space on paper or other substrates using a single printing process. As an additive colour system, RGB is reserved for luminous media such as screens or projectors. RGB colours are light colours; colour perception is created by mixing light. For this reason, it is also referred to as an additive colour model. The more colour is used, the brighter the image becomes. If all three primary colours are used at 100 per cent, the result is white.

CMYK, on the other hand, is the subtractive model. It consists of the three colours cyan, magenta and yellow, as well as the primary colour black, which are printed onto a (usually) white background. The more ink is applied, the darker the result becomes. The key colour is necessary because applying 100 per cent cyan, magenta and yellow does not produce true black, but only a dark brown.

An innovative new printing process

Boegli’s RGB printing, on the other hand, is printed on black paper and transitions into a brilliant white. This is made possible by reflective pigments in the colours.

“Using red, green and blue Spectraval pigments from Merck on a black background, I succeeded in 2013 in producing white by overprinting the three primary colours of additive colour mixing. This is achieved thanks to the reflective pigments in the inks,” says Boegli.

In the meantime,Merck and Boegli have further developed the technology and made it available for use with standard printers. RGB printing usingSpectraval™ works on conventional printing presses and can therefore be integrated into standard screen, gravure or flexographic printing processes.

The four main steps are:

1. The image file is separated into CMYK and placed on the negative. This produces the colours red, green and blue.
2. A fine screen ruling is selected for screening to ensure maximum ink coverage.
3. For printing, the special colour pigments are mixed in high concentrations into conventional screen-printing inks.
4. During the printing process itself, a low printing speed is important to ensure the ideal alignment of the individual pigments

To showcase the new RGB printing technology at drupa 2016, Merck collaborated with the company STAINER, which produced 3 mm thick, 2750 x 1875 mm aluminium composite panels for an RGB exhibition wall. To achieve this, the aluminium panels were first pre-printed in black using screen printing and then printed using the RGB printing process with the supplied design in the colours red, green, blue and silver-white.

More and more sectors are turning to RGB technology, as the impact of additive printing literally catches the eye of businesses and customers alike.