Paper specifications

Designation Description
   Humidity Percentage of moisture in the office paper is a critical indicator for working properties of paper. Usually office paper has lower humidity (about 4.2 to 4.5%) than offset paper (about 5.0 to 5.5%). That is because the office paper is exposed to significant heating in almost all models of copiers. Having low humidities, paper is more stable during the changing of the size and geometry, and less exposed to temperature extremes. Thus, the paper is less likely to twist or wrinkle under the influence of the picture transfering  process, and we get a more compact / dense stack of paper to be published.
Opacity Opacity  is a measure of how much the paper itself prevents candling printed image made on the reverse side of the sheet to its front side. This index is particularly important in double-sided copying, when the press is put on both sides of the paper. There are several factors which influence the ‘opacity’ of paper. They are: basis weight, thickness, brightness (higher brightness, the lower the rate of opacity), and ash content. Generally, 89%  opacity is considered to be minimal for office papers, and for the more expensive varieties  this index is above 91%.
brightness

Brightness is a measure of light amount reflected from the surface of the paper.

There are different standards of measurement which are used to determine the brightness. The Tarrі’s standart is used in the USA, while in Europe and Russia the ISO standard is used. It causes some confusion while comparison . Usually brightness , according to ISO,  defines reflective paper at a single wavelength without the influence of optical bleaching agents (non RoHS), which are added during manufacture to improve the perception of whiteness.

One square meter weight Grammage or weight is the weight of one square meter of paper expressed in grams. Most office paper is produced with mass of 80 g / m².This weight is common, because it is generally considered the least weight of the paper, which has a hardness values and the thickness needed for good cross in modern high-speed copiers. Usually an increase in mass of the paper for more than 80 g / m². does not give better results while using paper. The laboratory method for determining the mass of the paper is simple weighing a small sample of a specific area on the laboratory scale and multiplying by a certain factor to calculate the equivalent of one square meter.
Whiteness

Whiteness is the complex property of visual sensation, characterizing the degree of approximation to the white object on the strength of its high-brightness, high throwing power and minimum hue (ISO).

Whiteness index is measured in percentage.

It should be noted that despite the fact that whiteness  is generally considered to be an indicator of paper quality, it is one of the characteristics most easily achievable in production. Whiteness itself does not guarantee that the other quality options  of the product are always better. For example, such options as curl or stiffness, which affect the working properties of paper, in fact, may be more important to satisfy the end-user with the quality of paper.

Thickness

The thickness of a sheet of paper is measured in microns. Thickness index itself can affect other paper characteristics such as stiffness or opacity, but it would be wrong to judge working properties of  paper according to this indicator. The thickness of the paper depends on the mass of the paper, ash content, the number of calendaring cycles, which were in the paper production process, and the type of fibers used to produce this paper.

Thickness is measured in the laboratory using a micrometer.

Roughness Roughness is a property that determines the smoothness of the paper surface, and is usually defined in units of “Bendsten.” Too rough paper can cause simultaneous capture of two or more sheets or jams in the copier, and the low density of the press (“speckled print”), especially in areas of large paper “filling”. Too smooth paper can be very “slippery” to be stuck in the copier and tend to lower hardness values. Usually, the optimal level of roughness is between 150 and 250 units Bendstena. There is a relationship between the roughness and thickness of the paper. Reduction of roughness (increased smoothness) of paper is achieved by increasing the pressure calender rolls in the paper production process, which simultaneously reduces the thickness of the paper.
Smoothness

Smoothness is a property which characterizes the surface of printed paper (the presence of macro-and microscopic irregularities). The gloss of paint layer on the print depends to a large extent on it: the higher the smoothness of the paper, the more gloss of paint film. Smoothness is determined on a special device and characterized by the time of the expiration of the volume of air between the sample of paper and the smooth plate tightly held to it.

Smoothness is defined in seconds.

Ash content “Ashes” or filler is added to the pulp for several reasons. The most frequently used in papermaking filler is calcium carbonate. It has an intense white color and its particles have less wood fibers. The addition of the filler increases opacity, whiteness and structure of the paper is aligned. The negative aspect of this process is the reduction of the thickness and rigidity of the paper. Most of today’s high-quality office papers contains from 18% to 20% ash, which provides the best combination of paper properties.
Stiffness Stiffness is a measure of resistance to bending of the sheet as it passes through the copier. It is also the most important feature for office papers and one of the main indicators of the working properties of the paper. Hard paper will pass through the supplying paper system better and with less possibility to jam. Stiffness of the paper is caused by weight, thickness, % content of filler and, what is most important, by characteristics of the fiber used in paper manufacturing.
Plumpness

Plumpness is measured in cm3/g.

Plumpness (cm3/g) = thickness (mm) / density (g/m2).

Plumpness  depends on the composition of the pulp used to make paper or paperboard. A significant number of pulp fibers previously dried or frozen helps to ensure a plump paper. Materials with short fibers  (eg, cellulose from hardwood) or materials that tend to shorten in the grinding process of sulphite pulp fibers, rejection of viscose pulp,  and a large amount of dry refuse also increases the plumpness of the paper.

Blending strength The property of paper which means the  resistance to bending and collapsing within the guaranteed operating time.

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