Printing in clear contrast

This piece started out as long ago as the first wide-format printer we owned. Having used the services of a conventional screen printer for many years and then going on to use a Gerber Edge, something capable of printing at a larger scale than the Edge, and with more flexibility than outsourcing, was always going to be on our shopping list. Not just us either; almost every company in the industry now either has access to, or owns, some form of wide-format printer.


What happens though if you need to print on clear film for some reason? A window graphic or maybe a display panel. Solvent and eco-solvent by their very nature are not opaque enough and, although it is possible to increase the density of ink to create effects, clients invariably expect their design to look just the same on a clear film as on white.

In the days when you simply laid up coloured vinyl, opacity was not an issue. The Gerber Edge could answer some of this need using a white foil, which you could use as a primer on darker coloured surfaces or a backing if printing in reverse on transparent media. Solvent or eco-solvent has not quite got there yet, but they were close.

Wide-format printing remains resolutely CMYK with the odd addition of light cyan, light magenta, and light black. Orange and green are another option that is starting to gain ground as it increases the gamut of colours you can hit. So why has white so far failed to make the mainstream and remained on the margins whilst other options are gaining ground?

Any takers?

In part, I am sure the main reason for the lack of popularity of white ink is that for probably 90 percent of the time, there is a white roll of vinyl in the printer. Another reason could be that managing white ink on a conventional printer takes some doing, both for the hardware manufacturer and the user. For many equipment dealers, having printers in the showroom equipped with white ink is not an option either. As one supplier put it, if you are not using it over time, most of it will end up in the waste tank.


White ink has as one of its components Titanium Dioxide, which gives us the white element in the ink. It is a heavy compound, which does not enjoy being suspended in liquid and therefore needs to be regularly agitated or circulated to prevent it settling in the system. It is probably for this reason that you see varying degrees of whiteness from manufacturers who have differing amounts of Titanium Dioxide in their white ink, creating a com-promise between being dense enough to be useable, but not so thick that it clogs the print lines and heads.



Most manufacturers have incorporated recirculation systems and some method of agitating the ink. One printer we have used had a reminder facility and it is as simple as taking the cartridge out, shaking it, and putting it back. Admittedly this is more frequent than you would think, but is a simple enough task to do to keep it working.

Slow your speed

Another important factor to consider when specifying white is to bear in mind speed. Not only does white have to run slower than conventional inks, but by specifying a white channel, potentially you will reduce the speed on some machines by as much as half by taking channels that could be firing CMYK and that is whether you are using white on your job or not.

It is not all bad news though. Careful planning could avoid any production bottlenecks. One dealer I spoke with has seen customers add a white capable printer to their business in the form of a 750mm version of the same make of printer they currently use, leaving the larger one in standard 2x4 colour format for their day-to-day work.



Where white ink comes into its own is on flatbed and UV printers. These machines are industrial class, and for the most part can cope with the fact that the Titianium Dixoide element is three to four times the rate of ‘normal’ ink.
 
Most flatbed printers are specified with white ink and tests we have done, we have also found that the white is much denser giving a better finished product, however, on darker substrates more than one layer of white was needed. Most printers have the ability to print a white layer between two layers of colour. But I have seen in the past several layers of white being printed before the colour has gone down. This adds time and cost which has to be factored into any costings, but I have also seen good results using the roll option on a UV flatbed to print white down onto transparent media.

HP, amongst others, have two offerings that allow the user to put white on the machine when needed, which is a semi-automated process so the sacrifice in productivity can be managed fairly effectively. If white or metallic colours are something you are considering, Summa have the DC series which uses ribbons, this could be worth a look, as it uses the thermal transfer method so spot colours and metallic colours are its forte.

One thing that has come out of this little look at white ink is there are options in terms of equipment and as with any other large purchase you need to look at them all as they all differ slightly. There are even more options with UV but that can come with a hefty price tag. Some use white all the time, others less so, in some cases it is simply a means to an end rather than a central part of the creative process. It all depends on your market. There are business opportunities out there too as it is still a niche product, but if history is anything to go by it will not stay that way for long.



Looking at all the options on the market and the varying levels of sensitivity needed to use them, my own experience would tell me that to get the best out of white ink as a technology you need to be using it very regularly and have a dedicated production system setup to harness it. Like many such speciality technologies in our industry, only thorough testing and practice with it will yield the predictable results you want. Having seen what can be produced when it is done right, I would say white ink is worth the trouble, but only if you have the clients that require this type of output and if they are willing to pay a little extra for the trouble.


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