Support Characterization

There are four broad categories of paper: bond paper, inkjet paper, fine art papers, and coated papers.

Bond paper is the plain paper used in laser printers and office copiers. This paper is made of wood pulp, which contains cellulose fibers, and lignin and is sized with rosin. The sizing and the lignin eventually destroy the image.

Inkjet paper, of slightly better quality than bond paper, has improved external sizings such as starches, polymers, and pigments. These sizes make the surface of the paper whiter and more receptive to inkjet output.

Fine art papers such as Arches, Rives, and Somerset have been used for watercolors, drawings, and traditional printmaking. The papers are made from 100 percent cotton rag (alpha-cellulose), and there is no rosin sizing or lignin. Sometimes an alkaline buffering agent is added such as calcium carbonate. The fine art papers are usually combined with dye-based inks and used with IRIS printers.

Coated inkjet papers have a receptor coating to aid in receiving the inks. Coated papers can closely resemble traditional color print supports. These coatings create a higher-color range (especially for pigment-based inks), better image quality, greater brightness, and ink stability, which make them less likely to bleed. Coatings may include materials such as silica, clay, titanium dioxide, calcium carbonate, and various polymers (Johnson 2003: 235, and Jürgens 1999: 43). There are many types of coated papers on the market. In general, one of the coatings listed below can be applied to a standard resin-coated paper (a paper base sandwiched between two polyethylene layers), which reduces curling from heavy ink or a paper-based support. One can categorize these coatings as follows:

Swellable polymer: a nonporous coating made with organic polymers that expands and encapsulates the ink after it strikes the paper. The coating increases brightness by keeping the colorants from spreading and protects the image from atmospheric pollutants. These papers are best used with dye-based inks. (Johnson 2003: 237)

Microporous: these coatings were developed for rapid ink uptake since swellable papers have the disadvantage of slow ink drying, loss of gloss after printing and curling before and after printing. Microporous coatings contain small, inorganic particles dispersed in a synthetic binder such as polyvinyl acetate (Tarrant 2002: 30) or polyvinyl alcohol (Kasahara 1998:151) which create holes in the coating. The ink is absorbed into these holes, which results in faster drying and prevents the ink from smearing. The paper has a higher resistance to moisture and humidities. However, the colorants are susceptible to atmospheric pollutants and cause the color in the print to shift.2 These papers offer excellent image quality and can have a glossy, luster, or matte finish. They are best used with pigment-based inks.

In short, a swellable paper is slower to dry and remains sensitive to high humidity levels. However, it offers protection to dye colorants by fixing them within the coating. A microporous paper dries quicker, is less sensitive to humidity change and provides less protection to dye-based inks. Pigment-based inks should be used with microporous papers.