By: John Crumbaugh, Senior Marketing Specialist, Canon Solutions America
Here’s a bold statement—the first color you have to consider managing when using inkjet technology is the paper. Inkjet is not a four-color process. It’s a five-color process.
How can that be? Consider the three main print technologies of offset, toner, and inkjet. When printing on a toner device, the toner particles sit on the surface of the paper so the paper does not impact the color very much. With offset technology, the ink absorbs into the paper slightly. However the vast majority of the color remains at the surface, so there are more color differences using different papers on an offset press than on a toner device. But the greatest difference in color caused by paper occurs with inkjet technology.
The major component of inkjet ink is water so the substrate needs some absorbency to help the ink dry. This is important for fast production and the proper operation of downstream finishing equipment. In offset and toner printing, the colorant stays primarily on the surface of the paper so the interaction of the toner or ink particles with the paper fibers and the paper chemistry is minimal. With inkjet printing, the colorant gets absorbed into the strata of the paper. In effect, the image is printed into the structure of the paper. Therefore, inkjet images are influenced much more by the formation fibers and fillers that go into making paper than are offset or toner technologies. Ink and paper together make the color gamut in inkjet printing.
Of course, cost, quality, and value must all be taken into consideration when selecting the best media for any given application. The ink and paper chosen will determine the color gamut and aesthetic appearance. The business use will determine whether any additional cost to achieve the maximum color gamut and appearance are necessary. The key point is that there are many options available. The market is changing so rapidly that what we knew last year is out of date this year. As new products come out, new opportunities arise, and people are constantly needing to re-educate themselves.
Since the inkjet paper chosen has such a major impact on the quality of the output, it’s important to understand the three major categories of inkjet papers:
- Untreated papers—These papers have no special treatment for inkjet printing. They are primarily used for monochrome printing when color saturation is not necessary. They are available in various opacities to minimize show-through. Since there is no coating or treatment to help keep the ink colorant on the top of the sheet, more ink penetrates the paper’s surface yielding images that are softer with a smaller color gamut. Opacity is also affected by inkjet in that the opacity values are based surface readings and not inkjet printing which penetrates the paper.
- Inkjet treated papers—These papers contain treatments that are added during the paper making process. The treatment is throughout the paper allowing the colorant to sit higher on the surface of the paper. This provides better results in terms of clarity and color gamut. These papers cost more than untreated papers but may also require less ink since the colorant is trapped closer to the paper surface.
- Inkjet coated papers—These papers restrict the amount of colorant that can be absorbed by the paper thereby allowing the colorant to stay on the surface of the paper. The result is a broader color gamut than either of the other two paper types. These papers are more difficult to make. As a result, the range and availability of these papers is limited, and many come at a price premium
Inkjet ink also impacts the specific colors that can be reproduced. As the ink is absorbed into the paper, the shade, brightness, and saturation of the printed color can change. The deeper an ink absorbs into the paper, the more muted the color becomes.
There are two basic inkjet ink types—dye and pigment. With dye inks, the colorant is molecular; with pigment inks, the colorant particles are solid and opaque. Typically dye inks will be absorbed more deeply into the paper. The colorants in pigment-based ink tend to sit higher on top of the paper and are more light and fade resistant.
Inkjet treated and coated papers can be tailored for either dye or pigment ink to maximize the color gamut. An inkjet paper formulated for dye ink will have a larger color gamut when dye ink is used on that paper. Correspondingly, a paper formulated for pigment ink will have a larger color gamut when pigment ink is used vs. dye. The print application often governs whether dye or pigment ink is the best choice. Originally dye-based inks were less expensive than pigment inks, but that has substantially changed with the cost differential between the two becoming smaller.
With inkjet technology, color management becomes more critical because the interactions between paper and ink need to be managed well for optimum results. That is why inkjet printing paper is the number one component in defining the level of color quality.