Inkjet paper

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Paper for inkjet and laser printers in a store.

Inkjet paper is a special fine paper designed for inkjet printers, typically classified by its weight, brightness and smoothness, and sometimes by its opacity.

Manufacture[edit]

Main article: Paper machine

Inkjet paper is made from high quality deinked pulp or chemical pulps and requires good dimensional stability, no curling or cockling, good surface strength, and surface smoothness. Sufficient and even porosity is required to counteract spreading of the ink. For lower quality printing, uncoated copy paper will suffice, but higher grades require coating. The traditional coatings are not widely used for inkjet papers. For matte inkjet papers, it is common to use silica as pigment together with polyvinyl alcohol (PVOH). Glossy inkjet papers can be made by multicoating, resin coating, or cast coating on a lamination paper.

Comparison to standard office paper[edit]

Example cheap uncoated paper heavily soaked with ink, showing the back of the paper. The moisture-soaked fibers swell and revert to their original shape, showing the mesh belt webbing used in the paper manufacturing plant.

Standard office paper has traditionally been designed for use with typewriters and copy machines, where the paper usually does not get wet. With these types of paper, moisture tends to wick through the fibers away from the point of contact to form a disk. For an inkjet paper, this spreading results in the ink spreading out in the fibers to form a large smudge which lacks pigment intensity.

High-quality inkjet printing with dark, crisp lines requires the paper to have exactly the right degree of absorbency to accept the ink but prevent its sideways spread. Many general-purpose office papers of weights around 21 to 27 lb (80–100 g/m²) have been reformulated so that they can be used equally well with both inkjet and laser printers. However, this category of paper is only suitable for printing text, because the ink load is light.

When paper is manufactured, it is formed from a fiber mat that collects on an open mesh screen, which is then dried and pressed flat and smooth. Large areas of inkjet color, such as found in graphics and photographs, soak the paper fibers with so much moisture that they swell and return to their original shape from before pressing, resulting in a wavy buckling of the paper surface.

Double-sided inkjet printing is usually not possible with inexpensive low-weight copy paper because of bleed-through from one side to the other. Heavier weight paper works better due to the thickness of the fibers limiting bleed-through.

These papers are also unsuitable for photographic work because standard office paper is usually not "white" enough. This results in a poor color gamut and leads to colors being described as "muddy".

For all types of paper, the settings in the printer driver must be adjusted to suit the paper, so that the right amount of ink is delivered.

Inkjet photo paper[edit]

Photo paper is a category of inkjet paper designed specifically for reproduction of photographs, which is extremely bright white due to bleaching or substances such as titanium dioxide, and has been coated with a highly absorbent material that limits diffusion of the ink away from the point of contact. Highly refined clay is a common coating to prevent ink spread.

The best of these papers, with suitable pigment-based ink systems, can match or exceed the image quality and longevity of photographic gelatin-based silver halide continuous tone printing methods used for color photographs, such as Fuji CrystalArchive (for color prints from negatives) and Cibachrome/Ilfochrome (for color prints from positive transparencies). For printing monochrome photographs, traditional silver-based papers are widely felt[by whom?] to retain some advantage over inkjet prints.

Photo paper is usually divided into glossy, semi-matte, semi-gloss, "satin" or "silk", and matte finishes. The thickness of photo paper varies over a wide range. The lighter weights are not much different from general-purpose office papers as described above, and can be used for all types of printing, although these are the least expensive lowest-quality photo paper.

Photo papers for more critical work are thicker and have advanced coatings, sometimes with quick-drying properties. They can normally be printed only on the one specially coated side. A few papers are coated for double-sided printing.

Glossy photo paper, which is generally the most popular, has a shiny finish that gives photos a vivid look. It will generally be smooth to the touch and will have some glare to it. Matte photo paper is less shiny and has less of a glare than glossy paper. It is often used to produce superior text results. Matte and glossy prints will typically feel different to the touch, but when displayed under glass their results will often look quite similar. To increase the resemblance to oil paintings, papers with an imitation canvas texture are available. Photo papers are usually high-brightness neutral white papers, but a few off-white papers are made.

As in offset litho printing and traditional photographic printing, glossy papers give the highest color density (or Dmax), and therefore the widest color gamut. Photo papers vary in their longevity and their color gamut. Ink suppliers often provide color profiles for their ink systems when used with specific papers. Longevity depends on the specific combination of inks and paper. For maximum life, the paper substrate will be "woodfree" (i.e. wood-based but without lignin), or cotton-based, or a combination of the two. Plastic substrates also exist.

No official paper industry definition exists for glossy, semi-matte, etcetera, although an objective scale is available for the glossiness of papers used in offset litho printing. Such paper suppliers as Hewlett-Packard, Epson and Kodak all use their own terms to describe their paper, such as Everyday (HP), Premium High Gloss and Luster (Epson) and Ultima (Kodak). ECI (www.eci.org) has categorized papers for proofing simulation of litho papers (type1/2 etc.)

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