Although silver-halide and thermal printers require special papers, inkjets will print on almost any surface. In fact, the way your printed digital images look, and how well they age, depends a great deal on the paper you print them on and how you store them. If you're just printing copies to hang on the refrigerator door, you're probably not thinking about this. After a few months, when the pictures have shifted to green, or faded, you'll just toss them. But there are times when you don't want to be so casual with your prints. Since it takes time to capture, edit, and print images it's nice if they last long enough to be enjoyed by generations to come.

Paper Types

There are four common types of photo-quality inkjet paper: RC, cast coated, and swellable papers usually used with dye inks, and cotton rag fine art papers used with pigment inks.

• RC (resin coated) papers are constructed much like silver-halide resin coated paper so they feel like traditional pints. A sheet of paper is sandwiched between layers of plastic and the top layer is coated with a polymer designed to receive the ink. If you put a drop of water on this layer, it is slowly absorbed and dries without leaving ripples in the paper. Images stay glossy because the ink is absorbed by the polymer layer and not the paper base although the water resistance of the top layer varies from brand to brand. These papers have the widest color range (gamut) and can be divided into three sub-categories based on their finish:

  Glossy, called an F surface, has a very shiny, almost reflective surface.

  Luster/Satin, called an E surface, has a bumpy repeating surface that varies in depth depending on the manufacturer

  Semimatte, called an N surface, has a luster without any texture.

  If you gently bend a corner of an RC paper, you'll hear a slight cracking sound. You can even bend a print somewhat without creasing it. The paper also resists tears, kinks, and abrasions. An anticurling layer on the back side keeps the print flat, even when it's humid or large amounts of ink are used on the front side.

• Porous papers, also called microporous, nanoporous, nanoceramic, microceramic or photobase, often have banners on the package reading "Quick Dry" or "Instant Dry". They have short drying times because they are so absorbent that water in the ink evaporates more quickly. However, their longevity is less than that of other papers. When combined with dye-based inks,these papers are susceptibility to damage from ozone. One way to identify a microporous high-gloss paper is to rub your finger across its surface. It will squeak and prevent your finger from sliding smoothly because the paper is so absorbent it absorbs the tiny traces of oil and moisture on your finger that would otherwise act as a lubricant on a smooth surface.

  If you immediately frame one of these prints behind glass, the inside of the glass may fog. This fog, which looks something like a ghost image, is created by ink solvents leaving the paper before it is completely cured. These solvents dry at a slower rate than water so even when a print feels dry, they may not have completely dissipated. This process, called outgassing, occurs with all porous papers because these papers have a barrier that creates brighter, glossier prints by keeping the inks near the surface, but which prevents them from penetrating into the paper where they can dissipate. Other types of papers absorb the inks and do not have this problem. To prevent outgassing, Epson recommends you let a new print sit for 15 minutes, then place a sheet of inexpensive plain uncoated paper on top of it for 24 hours to absorb the solvents and accelerate the outgassing. If you are stacking prints, interleave plain paper between each pair. After 24 hours, if the paper is still wavy, replace the plain paper sheets and let the prints stand for another 24 hours. It also helps if you use proper framing procedures, including preventing contact between the print and the inside of the glass or UV acrylic.

  

  For your best images, look into fine art papers such as Hahnemuhle. These papers are more substantial and richly textured than other inkjet papers, and longer lasting. Some sheets, like the one shown here, are double-sided. Typically made from 100% cotton these papers are also acid-free with a neutral pH. Courtesy of Hahnem�hle at www.hahnemuhle.com.
 
• Cast coated papers have a coating that hardens in contact with a polished chrome surface that gives it an exceptionally glossy finish. The coating is an ink receiving layer on top of a paper layer, and prints dry quickly as ink is absorbed into the paper base. These papers fade in bright light and feel light weight. Too much ink can cause sections to wrinkle or bubble and even loose their glossy look. Once dry, a sheet with too much ink remains deformed just as plain paper does. You can also easily scratch the surface with a fingernail. Until recently these papers only worked with dye inks, but a cast coating designed for use with pigment inks is now available.
• Cotton rag papers, often called fine art papers, are not only more substantial and richly textured than other inkjet papers, they are longer lasting. Typically made from 100% cotton (except canvas which is usually 50% polyester) and coated with an inkjet receptive surface, these paper are also acidfree with a neutral pH. They come in at least two finishes, a smooth vellum and a textured velvet. Uncoated watercolor papers such as Arches, Somerset Velvet and Lanaquarelle are also fine art papers used for photos.

  Many fine art papers are made by the same traditional methods used for hundreds of years. For example, mouldmade papers are produced on a slowly rotating machine called a cylinder mould that simulates the hand-papermaking process using water, cotton fibers and natural gelatin sizing. Fibers become more randomly intertwined than in machine made papers, producing a stronger, more flexible sheet or roll. On many papers, a feathery deckle edge is the result of the natural runoff of wet pulp when making handmade and mouldmade paper, or created by tearing sheets while still wet. These papers last for centuries and are widely used for watercolors, acrylics, gouache, printmaking, and digital printing. In some cases, special versions of these papers have been introduced for inkjet printers.

• Speciality papers. Since any smooth surface can be coated with a layer that accepts ink, many materials can be made printable as long as they are thin and flexible enough to run through a printer. These include canvas, fabric, vinyl, transparent films, and transfer papers. One unusual example is Brightec's Night Luminescent Photographic Paper on which your images appear normal by day but luminescent at night.

Paper Sizes

Inkjet papers come in a range of sizes specified in inches, millimeters (mm) or by letters. Most photo printers can print on all sizes up to Legal (8.5 x 14), although when roll paper is used the length is much greater. Larger, yet still affordable, printers ($500 or less) print no larger than Super A3/B. For larger sizes you need to go to a service bureau or on-line printing service.

Paper Weight and Thickness

Papers can be partially described by their weight and thickness. Paper that weighs more and is thicker has a more substantial feel. These two measurements are often related, but not all thick papers are heavy and vice versa. The density of a paper may be low, but the sheet itself can be thick because of the way it's manufactured.

• Weight is often specified in pounds, or in Grams per Square Meter (GSM) with the later being a more reliable number to use when comparing papers. Pounds can be fudged so a reliable paper company will always list the GSM of their papers. A typical glossy paper's weight is around 260gsm.
• Thickness is specified in mils (thousandths of an inch). A typical glossy paper's thickness is between 10.4-12.5mil. Fine art papers can range between 13-17mil, so thick you may have to feed them into the printer one sheet at a time.

Selecting Paper

When considering paper for your images, here are some other criteria to consider.

• Finishes include glossy, semi-glossy, luster, velvet and matt. Rougher papers tend to scatter the light and lower the paper's color gamut (color range). If you look at a paper with a microscope, you can see that a glossy surface is less course and more uniform than a matt surface.
• Absorption refers to how a paper absorbs ink on its surface. Absorbent papers let liquid inks soak into the paper taking the color along with them leaving images that look faint and washed out. You'll get richer colors using coated papers that are less absorbent and designed specifically for photographs.
• Brightness is the measure of the amount of light reflected from the surface of a sheet of paper and is determined by industry standards. The brightness scale has a range of 0-100% and the higher the number the brighter the sheet is. Brighter papers provide more contrast and brighter colors.
• Opacity is determined by the thickness of the paper and the materials used to make it. High opacity prevents a print that is on one side of a sheet of paper from showing through to the other side. You can compare paper opacities by holding each sheet up to a light source or by placing them over a printed surface to see if the type shows through.
• Archival quality is an estimate of how long a paper will last without showing the traditional signs of aging such as fading, yellowing and brittleness.
• Watermarks are faint designs embedded in a paper when it is made, often to indicate the maker or brand. The translucent design or name is visible when you hold a sheet up to the light. Watermarks are created by a design sewn onto the papermaking screen with raised wire. When the sheet is formed, the pulp settles in a thinner layer over the wire.
• Rolls of paper can be used to print long panoramas but the printer has to have an attachment to feed the paper and the paper you want to use must be available in rolls.

Caring for Paper prints

• Do not fold or roll the paper, or scratch the printing side.
• Do not touch the printable side without cotton gloves or you can transfer moisture or oil to it.
• Store and use paper and prints at normal room temperatures and humidities. Don't use or store it in extreme conditions
• Print only on the printable side. With glossy papers it's easy to tell the printable surface (the shiny side) but for others it can be more difficult. Usually the printable side looks smoother when held at an angle to the light or whiter when flipped back and forth. Some paper will have a logo or other design on the nonprintable side. Occasionally, paper will have one corner notched.
• Choose paper and ink carefully because ink-paper combinations are somewhat unpredictable. Most companies recommend using their own papers and ink cartridges with their printers. With reliable companies (Epson and Canon to name a few), this is because they have extensively tested their materials and know these products work well together. Even the most responsible company can't possibly be expected to test them in combination with inks and papers from other suppliers. To be safe, stick with a trusted source for both paper and ink.
• When printing more than one photo, remove each finished print from the printer before the next one slides over it.
• Store unused paper in its original package.
• Specify the correct printer profile. When printing, one of the most important settings you will make is the one in a dialog box where you specify a printer profile so the printer knows what kind of paper is being used. Different papers require different amounts and mixes of inks and if you specify the wrong type of paper you won't get optimal results. To find generic printer profiles, visit the site of the company that made or sold you the paper. They are often offered as free downloads.