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Papers for digital printing

Oct 1, 2005 12:00 AM

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Once a paper or specialty media product has been selected, it has to be stored, handled, conditioned and loaded properly to maximize performance and machine productivity. Here are some useful tips.

Proper storage
Paper normally is shipped in cartons. If a large quantity has been ordered, the paper typically arrives on wooden pallets. These pallets and cartons should be handled carefully. Although designed to withstand the demands of normal shipping, the cartons do not afford protection against damage if they are thrown, shoved, dropped, struck or poked by a forklift. Mishandling of the cartons can result in physical damage to the paper, some of which might not be immediately obvious; that, in turn, increases the rate of jams and other feeding and imaging problems.

Do not store paper directly on the floor, because that increases the possibility of moisture absorption. Paper should be stored on pallets or shelves, or in cabinets in an area protected from extremes of temperature and humidity.

Do not open sealed reams of paper until you are ready to load them into the printer. Leave paper in the original ream wrapper, and leave the reams in the shipping carton. The ream wrapper contains an inner lining that protects the paper from moisture. Removing the ream wrapper eliminates that protective moisture barrier and, depending on the environment, that can result in the paper losing or absorbing moisture. Paper is very sensitive to moisture changes and this fluctuation can result in excessive curl, wavy edges, tight edges and other quality issues.

If cartons or individual reams are to be stacked, they should be placed carefully on top of one another to avoid crushing the edges or causing any other damage.

The temperature of the room where paper is stored can have a significant effect on how that paper performs in the machine. Optimum paper storage and printer operating temperature is 68 to 76 degrees F (20 to 25 degrees C).

Humidity control is essential to ensure proper paper handling and performance. Optimum storage conditions include areas with a relative humidity of 35 percent to 55 percent. Automatic control devices are not always reliable. The areas must be continually double-checked using an accurate instrument. Even when functioning properly, overloading of the storage or work area with external air from open doors and excessive in-and-out traffic can defeat environmental control systems. Upward or downward adjustments in relative humidity (and sometimes temperature) might be needed to compensate for environmental variations.

An increase in humidity can cause paper to develop wavy edges resulting in jams and misfeeds. This can occur because the edges absorb moisture while the rest of the ream remains unaffected.

When there is a decrease in humidity, the edges can lose moisture. They then contract, causing “tight edges.” This, too, leads to jams, as well as faulty registration and wrinkles during printing.

If paper shows signs of waviness or tight edges, a change in relative humidity might help. In general, it is best to adjust the relative humidity in increments of no more than five percent to 10 percent, allowing time for any alteration to be fully effective before making further changes.

Conditioning paper
If paper is moved from a storage area to a location with a different temperature and humidity, the paper should be conditioned to the new location before use.

See the paper conditioning chart, below, for assistance in determining the amount of time needed to condition stacked, unopened cartons of paper.

Note: The top row of numbers indicates the temperature difference between the storage area and the operating environment, with the first number being degrees Fahrenheit and the second number being degrees Centigrade.

Paper conditioning chart
Temperature difference (degrees F/C)
10/5.5 15/8.5 20/11 25/13 30/17 40/22 50/28
Cartons Hours to condition
1 4 8 11 14 17 24 34
5 5 9 12 15 18 25 35
10 8 14 18 22 27 38 51
20 11 16 23 28 35 48 67
40 14 19 26 32 38 54 75

Example: If you want to move 10 cartons from a storage area with a temperature of 20°C to an operating area where the temperature is 33°C (a differential of 13°C), the 10 cartons should stand unopened in the printing room for a minimum of 22 hours prior to use.

The chart refers to moving paper cartons loaded together on a pallet. Separating the cartons or reams from each other can accelerate conditioning. Do not unseal the reams, however, until you are ready to load them into the machine.

Follow the arrow (North America only)
Because the front and back surfaces of the paper, as determined during the papermaking process, differ slightly, one side is preferred as the side to image first. The primary determinant of which side to print first is the paper’s curl characteristics.

If you are using a quality paper intended for digital printing, the ream wrapper will be marked with an arrow that points to the preferred printing side (see example, above). Print on this side when printing one side only; print this side first when printing on both sides of a sheet.

Whether this side is to be loaded up or down in the paper tray must be determined for each machine (and sometimes for each paper tray) by reading the system’s operator guide. Once you’ve determined the correct orientation, marking each paper tray with a label indicating the correct loading direction helps avoid operator error and lost productivity.

Loading the paper tray

Carefully unwrap the reams of paper to be loaded, taking care not to bend any of the sheets or otherwise damage the paper. Inspect the paper for any obvious signs of damage (bends, folds, crumpled or wavy edges, tight edges) or defects. Fan the paper as necessary to avoid sticking edges. Do not handle the paper any more than necessary.

Load the reams into the paper tray one at a time, taking care to observe the correct orientation, as indicated by the ream wrapper arrow.

When more than one ream is being loaded, it is important to make certain the reams are aligned atop one another. It is easy to wrinkle, bend or otherwise alter the top sheet of a lower ream when placing another one on top of it. The interface between reams in the paper tray is a frequent source of jams. It is particularly important to avoid loading successive reams inconsistently (some arrow up, some arrow down).

Observe the paper fill line marked on all paper trays and do not load paper above this line.

Storage and conditioning for specialty media Specialty media such as carbonless, labels, tabs and transparencies also have proper loading, storage and handling requirements. Review instruction sheets contained in the product packages.

Determining curl

In the event a paper ream is not marked for correct print-side orientation, it might be necessary to determine the curl direction yourself. Do this by holding a 1?2-inch stack of paper by one of its short edges. Let the paper hang with the long edge parallel to your body. Either the lower edge or the two side edges will be curling slightly toward the center. Observe which way the edge(s) curl. This is the curl side. Load the paper into the tray such that the side opposite the direction of curl is imaged first.

Note: If the ream has an arrow marking, it points to the opposite side. Load into the paper tray in the appropriate direction.aper tray in the appropriate direction.

Tamara Pope is manager of Worldwide Product Planning and Marketing Strategy for Xerox Supplies. Xerox offers a “Helpful Facts about Paper” resource guide on its Web site. See