Paper is the common factor between all Ricoh products—from original to copy, from fax to print, from A4 to wide-format. Paper is available in many different formats, weights, surfaces, structures, and colour—all influencing the quality of the final deliverable.
In addition, environmental factors—such as the period of time the paper is stored and the storage conditions used—can influence the paper characteristics.
Temperature and humidity affect the quality of print on the paper.
This fact sheet details these characteristics to help you and your customer choose the right paper for the job.
In the offset industry, paper is selected per job based on the requirements of the final deliverable such as a book, magazine, or calendar. In an office environment, paper is selected based mainly on its price.
Choosing the right paper is as important as choosing the right digital press. The right type of paper for a digital print job is directly related to the quality of the printed material and the productivity of the digital printing system.
Anatomy of paper
Paper is thin material mainly used for writing or printing upon, or for packaging. It’s produced by pressing together moist fibres, typically cellulose pulp derived from wood or grasses, and drying them into flexible sheets.
What are the components of paper?
| Components | Coated | Uncoated |
| Fibres | 50% | 70–75% |
| Coating | 30% | 0% |
| Filler | 10–13% | 16–23% |
| Water | 5–8% | 4–7% |
| Starch and other | 2% | 2% |
What is paper grain?
Paper grain is the direction in which most of the fibres lie. The grain is determined during the papermaking process when fibres tend to align in one direction or the other. Depending on how the paper is cut, it can be identified as either:
- Short grain paper—the grain is parallel to the paper's short side
- Long grain paper—the grain is parallel to the paper's long side.
Folded documents
Paper should be folded parallel to the grain direction. Paper folded against the grain may be rough and crack along the folded edge. The heavier the paper, the more likely roughness and cracking will occur. For heavier paper, to avoid cracking along the folded edge, the paper should be scored before folding.
Selecting media
Customers who are moving from offset to digital printing expect to print on varied paper, primarily because they have always been able to with their offset devices. It’s important to get customers to agree to use only 2 different types of tested and approved paper—coated and uncoated—by promoting these 2 benefits:
- Overall reliability will be improved
- Only carrying 2 types of paper will improve profitability and reduce waste.
When suggesting paper to a customer, select paper based on:
- Coating type
- Availability
- Grain direction
- Sizes and cutting
- Packaging
- Consistency of supply.
Occasionally a sales region will conduct its own tests on paper and use the results to provide advice to their customers. Some of these tests and results are available—consult with your sales company for more information.
Paper storage
Paper is living material that is sensitive to changes in humidity, temperature, and light.
Paper absorbs and releases moisture into the air causing it to curl, influencing it’s electrostatic characteristics.
Paper shrinks when it loses water and swells when it gains water. Fibres in the paper swell and shrink with humidity changes, mainly in the cross direction.
Light intensity from different sources can cause paper to discolour. It’s advisable to store paper in a dry and dark environment, sealed in its packaging until required.
Paper inside the paper tray of a device is also affected by humidity changes. If paper usage for the device is low, it’s best to replenish the paper tray as required and to store the open package properly.
When storing paper, provide conditions that are as stable as possible. High temperatures and humidity levels speed up the degradation of the paper and encourage mould growth.
Fluctuations cause distortions and subsequent damage to paper items. The optimum storage conditions are 18-22°C and 45-55% relative humidity. These conditions are difficult to achieve without specialist air-conditioning systems—but it’s possible to apply some basic but important principles that will make a difference, such as not storing paper in direct sunlight and placing paper in a cupboard free of moisture.
Paper weight, paper path, and fusing
Paper weight
Paper weight, or paper density as it’s sometimes known, is an important specification for Ricoh devices. Paper weight is expressed in grams per square metre (g/m2) of paper.
Paper weight or paper density is the concentration of paper fibres (and other materials) per sheet of paper. The heavier and stiffer the paper—the more difficult it is to bend it.
Paper path
The curvature of the paper path in a device limits the maximum paper weight. Paper that is too heavy or too light can cause paper jams inside the device.
The paper path is the combination of selected paper tray, duplex unit, and finishing function—or all of these. The duplex unit can have a tight curvature, limiting the maximum paper weight for duplex jobs.
Fusing
When determining the maximum paper weight to be used on a toner-based device, you also need to consider the setting on the fusing unit.
A combination of heat, pressure, and the speed of the paper travelling through the fusing unit melts the toner and presses it into the fibres of the paper.
If this combination is not optimal, the toner melts incorrectly—either not enough or too much—resulting in poor image quality.
The user must change this combination by applying the correct paper weight settings on the device or in the printer driver.
Paper surface
When feeling the paper surface of a book, newspaper, or glossy magazine, you will notice differences in the paper surface from rough to smooth.
A rougher surface improves the readability of the document as the surrounding light is reflected in all directions, and not only into the eye of the reader—so there is less glare. This is a characteristic of uncoated paper, so it’s best used for publications such as books—which demand long and uninterrupted attention from the reader.
A smoother surface is more suitable for colour reproduction, or when very fine details such as very thin lines are required. A smoother surface will allow the ink and, to a lesser degree, toner to stay on the paper surface and not spread so much into the paper fibres. This is a characteristic of coated paper and it increases the glare from the surface.
Coated and uncoated paper
Coated paper is paper that has been coated with chalk or china clay and bound synthetically to the paper, or naturally with starch. This coating imparts certain qualities to the paper, including weight, improved surface gloss, and smoothness or lower ink absorbency.
The coating can have dull, gloss, matte, or other finishes. Coated paper generally produces sharper, brighter images, and has better reflectivity than uncoated paper.
Coated paper is typically smoother and is less absorbent than uncoated paper. These characteristics make it more suitable for certain types of overprint finishing techniques such as flood or spot coating with varnish or other finish coatings.
To grade the smoothness (level of gloss) of coated paper, paper manufacturers may use these names or descriptions:
| Level | Common names |
| High gloss | Cast, chrome coated, cast coated |
| Gloss | Gloss, enamel, art |
| Semi-gloss | Dull silk |
| Satin | Satin, velvet |
| Matte | Matte, reply card |
Uncoated paper is paper that doesn’t have any kind of coating—such as clay or latex. It’s available in many different finishes, colours, and weights. Uncoated paper is more absorbent than coated paper and typically used for letterheads, copy paper, or printing paper.
The finish of paper—level of smoothness and roughness—is determined during the production process. During the pressing stage, it passes through a series of rollers. Increasing the number rollers in the process results in smoother and glossier uncoated paper.
The paper finish can significantly affect the image quality. If the surface is too rough, the toner may not fuse properly and colour may appear duller and darker. With the oil-less toner, a mottled image on rough surface paper is improved by a smoother toner surface on the paper producing a sharper, more even image.
Offset vs digital printing
The basic processes for offset and digital printing are different and require different paper demands.
Offset printing uses liquid ink in an absorption process that doesn’t require heat to print on paper. Using digital, printing transfers dry toner or ink electronically to the paper, and uses a high temperature to fuse the dry toner or ink to the paper.
There is a direct relationship between the performance and productivity of production printers, and the design and quality of paper used. Different types of paper are produced for different types of printing.
Using offset paper in a digital colour printer can result in mottled appearance, poor fusing, jams in a stacker, paper curling, and excessive dust or contamination.
These are the key risks and problems when using offset paper in a digital printing device:
| Risk | Problems |
| Porosity | |
| Fuser roll oil absorption | Contamination risk Image quality Paper jams |
| Moisture | |
| Impacts the electrical charge Paper curl and waviness | Print mottling Light and dark areas on the print |
| Dimensional stability | |
| High temperatures from fusing can cause paper curling | Paper jams Stacking issues Duplex printing issues |
Digital optimisation
It’s the process by which paper and specialty media products are developed, designed, and produced to ensure optimum performance on digital printing systems. This process includes stringent product specifications, quality control and assurance criteria, converting or finishing requirements, and supplier training and education.
The differences in paper used in offset and digital workflows are described in this table:
| Digital paper | Offset paper |
| Paper stiffness | |
| The paper is stiffer than offset Printing is affected by the stiffness of the paper—for example, paper jams stem from poor paper stiffness At the time of papermaking the stiffness of the paper is taken into consideration | Priority is given to the printing and the feel of the paper rather than the stiffness At the time of papermaking the stiffness of the paper is taken into consideration |
| Electrical resistance | |
| Electrostatic properties of the printer are set to optimal for the transfer efficiency of the toner | Electrostatic properties are not taken into consideration |
| Moisture content | |
| Paper moisture is set to 4–5% to prevent paper curl after printing Paper with high moisture content tends to curl | Paper moisture is set to 6–7% to enhance printing |
| Air permeability | |
| The paper has high air permeability to eliminate the influence of the heat from the fuser Low air permeability may cause paper wrinkling | Air permeability is not a factor in improving the printing process |
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