Printing & Design Tips: NOVEMBER 2005, Issue #52

Inkjet Inks and Paper

An entire book could easily be written about inkjet papers and inks (and many already have been). The following is in no way intended to be comprehensive, but rather to give you a starting point, a vocabulary, to help you ask questions. Your printer will guide you through the rest.

First of all, if you’re printing display signage for a trade show or any other large-format single image, you will want a printer with digital imaging capabilities. Not all offset printers have such equipment and knowledge. Vendors tend to specialize in either offset or digital work, although you may be pleasantly surprised to find out that your old tried-and-true printer has sprung for some new equipment.

After you find your printer and tell him about your job, you may first want to explore the various surfaces on which you can print with an inkjet printer. They run a wide gamut. You can print on paper, plastic, and glass. You can create faux art prints on canvas. Everyone has seen the back-lit displays in the subway, essentially inkjet ink sprayed on transparent plastic and then lit from behind. You can even print on food (with the proper non-toxic inks). For example, photographs can be printed on birthday cakes.

Second, consider the physical qualities of your intended surface. When printing on a non-porous surface such as glass or plastic, you would use solvent-based inks. The solvent in these inks will be flashed off (caused to quickly evaporate through the application of heat), leaving only the ink colorant on the printed surface. Water-based inks, on the other hand, could not be used on plastic or glass, since they will not sit up on top of the printed surface. Water-based inks need something to soak into (e.g., paper). Paper is porous; glass is not.

Next, you need to consider whether the large-format ink-jet image will be used inside or outside. The kind of ink your vendor chooses will depend on your answer. Dye-based inks are used indoors only; pigment-based inks are used indoors and outdoors. What’s the difference? Pigmented ink-jet inks are composed of colorant (usually a metal or mineral) molecules suspended between the molecules of the ink vehicle (water or solvent: the liquid that makes the ink fluid). In dye-based inks, the colorants have already been absorbed into the vehicle (usually water), creating one homogeneous solution. Outdoors, because your large-format print will need to withstand the sun (UV radiation) and rain, you need to use pigmented inks--normally pigmented inks suspended in solvent. This kind of ink is generally toxic and more expensive, but it is necessary for most outdoor signage. Also, remember that these inks will let you print on non-porous surfaces.

Finally, consider color accuracy (called color fidelity). Many ink-jet printers (all of which start with a four-color process ink set just like an offset printing press) have added two or more additional colors, usually light magenta and light cyan. Some also add even another black ink. Why? Because not all colors (some PMS colors in particular) can be approximated with only four inks. Adding the extra colors to the ink-set expands an ink-jet printer’s color gamut to more closely approximate a wider range of PMS colors. Discuss this with your printer to ensure a satisfactory result.

Armed with this information, you have a starting point from which to choose a vendor and begin asking questions. Using this common language, you will be able to describe the results you are looking for and the concerns you may have.

One final note: a good way to start your search for a vendor with large-format ink-jet capabilities is to ask your offset printer (whom you trust) to suggest a vendor that focuses on “signage” or point-of-purchase displays (i.e., the plastic or cardboard pop-up displays in retail stores). The Internet is another good resource for finding these printers.

What is a Freesheet?

A freesheet, which your printer will distinguish from a groundwood sheet, includes no more than 10 percent mechanical wood pulp. Mechanical wood pulp exists only in the two lowest grades of paper stock.

Why does this matter to you?

The impurities in a groundwood sheet will cause the paper to age and yellow more quickly. This may not matter if your publication is designed to be read once and then discarded, like a newspaper. If, on the other hand, you are printing an annual report that will (hopefully) be kept and reread, you might choose a freesheet.

Also keep in mind that a freesheet will be brighter than a groundwood sheet--an added plus for a high-profile publication. Not surprisingly, freesheet paper stock is incrementally more costly, depending on the quality of the paper stock you choose.

[Steven Waxman is a printing consultant. He teaches corporations how to save money buying printing, brokers printing services, and teaches prepress techniques. Steven has been in the printing industry for thirty-three years working as a writer, editor, print buyer, photographer, graphic designer, art director, and production manager.]