By Francis Atterbury
Ultra Violet has been chosen by Pantone as its ‘Colour of the Year’; to resounding cheers from the fashion community and groans from the printing industry, I’d imagine. I love colour, and I definitely love violet, but it is impossible to achieve from a conventional four-colour set. The closest you can get is 100% magenta and 100% cyan. But, in offset litho, ink is transferred from the blanket of a press to the paper by virtue of the fact that paper has more ‘tack’ than the blanket and thus ink is pulled from one to the other. However the usual printing colour sequence sees magenta and cyan next to one another and, faced with a solid coverage of ink, the next colour in the sequence will not be able to transfer from the blanket to the paper; this is called ‘refusal’. So, if the magenta goes down first, not enough blue will transfer and vice versa.
There are workarounds to this; changing the printing sequence (though this can have unexpected effects on colour in other areas) or by using a press with space for more than 4 colours in one pass and leaving gaps. Even then, it’s difficult to print without any refusal and any colour achieved won’t be true violet, or even anywhere particularly close. Even a press that employs UV drying after each unit will still end up with a poor relation to violet. Digital printing (HP Indigo) has very similar problems, although to a lesser extent.
An expensive solution in both offset litho and offset digital printing is the use of enhanced process colour sets – essentially the addition of one or more colours (usually an orange, an actual violet or a green) to the conventional four-colour set. This isn’t always easily proofed and it’s also not always appropriate where there is only a small amount of purple.
Strictly speaking Ultra violet refers to a wavelength beyond violet and outside our the visible spectrum – the last colour we can see on the rainbow! But once you realise that colour is just a figment of our imagination, there’s really no return…
For most, where purple or violet are crucial, we think the best solution (especially for Pantone) is to create a 5th colour and print CMYK + PMS Ultra Violet. Or try to balance things out with a bluer cyan or more purple magenta and see what happens; sometimes, trial and error will get you closest!
Top image from the Islington Chapel Books by graphic artist Billie Temple.