When it comes to printing, paper is only one part of the equation. What about the inks?

Inks produced using vegetable oils can be made from a variety of sources including soy-bean, corn and linseed oils. Using these types of ink reduces or even cuts out volatile organic compounds (VOCs) emissions. These emissions not only combine with vehicle exhaust to form photochemical smog, but in liquid form VOCs can effect water and soil quality.

More and more printers are using these vegetable based inks so it's worth enquiring.

Even the more
exotic can be acommodated. Completely mineral oil free metallic inks were launched in February 2007 in all the standard pantone references and can also be blended with Pantone Inks (NPS) to produce Pantone polymetallic colours and other standard metallic colours.

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Visual colour mixing is nothing new, it is the whole basis of Pointilism after all. Go and look at Seurat's 'The Bathers' in the National Gallery for a perfect illustration of how the human eye naturally blends individual dots of colour to create a new palette.

Put simply, traditional halftone screening (also known as AM or amplitude modulated) uses dots of colour in varying sizes arranged in a regular pattern. Whereas Stochastic screening (also known as FM or frequency modulated) uses dots of the same size grouped with greater or lesser degrees of density. Traditionally an area of darker tone is produced by increasing the the size of the dots in the halftone pattern, with FM more dots of the same size are grouped closer together. But why does it matter?

There are three main advantages to FM screening:

1. Because there is no regular pattern involved the visual effects of mis-registration of the plates (or moiré) is greatly diminished.

2. The dots used in FM screening are smaller overall than AM and this results in improved image definition. A bi-product of this, some believe, is an increased colour gamut.

3. Again because the dots used are smaller and constant in size there is an average saving on the amount of ink used of between 10 and 20%. Smaller dots minimise the effects of dot gain which again contributes to image clarity. And of course using less ink (particularly those made with mineral oil rather than vegetable oil - see the G Spot opposite!) adds to our green credentials.

Despite being introduced over a decade ago in the mid 90s, stochastic screening is still a bit of a speciality. This is partly due to the fact that accuracy in the plate making is vital and until CTP (computer to plate technology) became as commonplace as it is now the comparative instability of film was always going to be an issue.

So have we seen the last of traditional haltone screening? I don't think so. As with all print technology you will always find a horses for courses argument. There are even the devotees of the more recent hybrid systems...but that's another story.

Next month: sheetfed litho,
what it means and how it works