Paper Encyclopedia
A
Absolute moisture |
The quantity of water in the paper measured as a percentage of its weight. |
Age resistance |
The following factors distinguish a paper as being age-resistant:
- uncoated paper, that could be suitable for coating, manufactured from 100% bleached pulp
- pH value of 7.5–9
- a calcium carbonate share of at least 3%
These guidelines were laid down in DIN-ISO 6738. They cover the features which paper and cardboard have to fulfil in order to correspond to the required durability class (in Germany LDK). This standard is applied to paper and cardboard in the form of documents and books, for example, which have to be usable even after a longer period of storage.
Classification of the LDKs
LDK 24–85 – this class of durability fulfils the very highest demands
LDK 12–80 – several 100 years
LDK 6–70 – a minimum of 100 years
LDK 6–40 – a minimum of 50 years |
Air humidity |
Because paper reacts very sensitively to moisture fluctuation, a climate (humidity and temperature) which is as constant as possible is important for the storage of paper. In processing paper, a relative humidity of approx. 50–55% at a temperature of approx. 20°–22 °C has proved to be favourable. |
AOX |
Standard international unit of measurement for comparing the pollution of waste water with hydrogen chloride from various pulp factories. The AOX value constitutes the basis for division into “chlorine-free”, “low-chlorine” and “chlorine-bleached”.
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Auxiliary materials |
A large number of organic and mineral additives (e. g. glue, clay, paraffin, resin) and fillers (e.g. china clay, chalk) and dyes. They are necessary to give the desired characteristics to any paper. |
B
Base paper |
Natural paper which is produced in a paper mill and then finished outside the paper machine. |
Basis weight |
Feature differentiating many “paper thicknesses”. The value is determined from the weight of
1 square metre (=g/m2).
7 g/m2–150 g/m2 = paper
150 g/m2– 600 g/m2 = cardboard
over 600 g/m2 = board |
Bleaching |
As the pulp has a yellowish to brown colour after chemical decomposition, the pulp is bleached using various processes. The result: white paper. |
Bleeding |
Is the flowing of different, adjacent colours into one another as in inkjet technology. |
Bleeding test |
An A4 sheet is cut from every roll to be tested and imprinted using an inkjet printer. Here a test image with adjacent colour areas is used. The test evaluates the bleeding of the various inks into one another. |
Blue Angel |
The environmental label of the German Federal Environmental Agency. The pulp used for these products must consist of 100% waste paper. The recycled papers must contain at least 51% waste paper from the lower and middle categories (groups I, II, IV, V). |
Brightness |
The light reflected from a paper sample is measured under standardised lighting conditions. It classifies the intensity of the apparent whiteness. The degree of brightness can be significantly increased using optical brighteners. Not to be confused with the whiteness, which takes the various colour nuances into consideration. |
Broke |
Paper which has been rejected due to defects or clipped edges arising during production. It can be returned to the production line for the manufacture of “quality goods“. |
C
Calender |
Smoothing machine made of steel and hard-paper (cotton) rollers. The paper web is subsequently fed through it and pressed (“super-calendered”) with moisture, pressure and heat. |
Calender stack |
Before being rolled up, the paper is smoothed under high pressure between steel rollers in the calender stack at the end of the paper machine. There are also soft-calendar stacks with a combination of steel and plastic rollers. |
Calendering |
Also known as “satin-finishing“. It is the mechanical smoothing of a coated or uncoated paper during manufacture. During this process, the paper web is guided between several rollers at very high pressure and temperature. |
Cardboard |
Its basis weight lies between paper and (thicker card) board. We differentiate between one-layer and multi-layer cardboard, which can be couched or glued. Multi-layer couched cardboard consists of several – not necessarily equal – layers of fibre which are formed individually on round or longitudinal screening machines or combined round-longitudinal screening machines, and combined while wet. The fibres in the individual layers become felted to one another (couching) before being further processed as a continuous web, i.e. pressed and dried. |
Cardboard (over 600 g/m2) |
Is of course thicker than cardboard (under 600 g/m2). It is also more stable. We differentiate between machine cardboard and grey mill board, packaging cardboard, technical and special cardboard.
Thickness is quoted in mm or in pieces (40s = 40 pieces in the format 75 x 100 cm for 50 kg). |
Cellulose |
The cell walls of the plants consist of this organic compound, the most frequent in nature. In wood, cellulose is compounded with lignin and other components of the cell wall. |
Chlorine bleaching |
Elementary chlorine is used to remove lignin during the production of pulp and bleaching. Lignin makes paper friable when exposed to oxygen, and allows it to yellow. The waste water from chlorine bleaching cannot, however, be cleaned sufficiently and therefore pollutes waters. For this reason, only chlorine-free alternative bleaching methods are now used. These do not pollute the environment. |
Chlorine-free paper |
Describes the bleaching process in the production of pulp. Paper which has been manufactured from pulp and has not been bleached with elementary chlorine or chlorine compounds is described as chlorine-free paper. The bleaches most used today are oxygen and hydrogen peroxide. Paper, the fibre-bleaching of which reduces water pollution, is described as “low-chlorine”. Here the pulp used is frequently bleached without chlorine gas (elementary chlorine) – chlorine dioxide is used instead. |
CIE |
CIE (Commision International de l’Eclairage) is a standard colour system for the measurement of colour values (e. g. degree of whiteness). |
Click price |
Price per copy (not including paper costs). |
Coated paper |
To achieve a closed surface and thus even better printability, a coating compound is applied to so-called coating base paper and distributed equally in the prescribed coating thickness. This coating process refines the surface of the paper. There are various coating procedures: china clay, chalk, casein and plastic dispersion. One-sided (= chromo paper) and double sided matt, semi-matt and glossy coating is possible.
Coating can either take place on-line (on the paper machine) or off line (on a separate coater). Coated papers make up the largest part of the high quality art papers sector. |
Coating machine |
The coating machine produces coated paper. It transfers a selected coat colour to the surface of the base paper or raw paper. |
Coloured papers |
Coloured papers are produced by adding colours and patterns (mostly manual designs) after manufacture (not to be confused with tinted papers). |
Continuous paper |
Rolled printing paper for continuous printing machines weighing between 40–80 g/m2, mostly woodfree but also paper with various percentages of secondary fibres. |
Copy paper/ laser printing paper |
Paper which is exactly attuned to the requirements of copy machines. Temperatures of up to 200 °C temporarily arise during both copying and laser printing. This requires a particularly heat-resistant paper with a specific degree of smoothness, moisture and runnability. These papers contain less moisture than offset papers (relative humidity of 30–35%). |
Cross-cutting |
A process for finishing paper. The paper and cardboard webs are produced on rolls and then cut in a cross-cutter, first longitudinally and then transverse to the machine direction, thereby achieving the desired formats. Depending on the grammage, several rolls can be cut at the same time. |
CTMP |
Chemo-thermo mechanical pulp. A raw material gained from wood which is broken down chemically, thermally and mechanically. The yield then amounts to 95 % (similar to ground wood pulp). The raw material thus extracted is not bleached but rather processed further while maintaining its yellowish coloration. |
Cut/cut edge |
The paper taken from the roll for formatting is initially cut longitudinally on cutting aggregates using so-called slitters. This is followed by cross-cutting, with either rotary or chopping cross-cutters.
Important when cutting: dust-free without fraying, accurate format, perfect right angles. |
Cut size |
Paper formats DIN A4 (210 x 297 mm) and DIN A3 (297 x 420 mm). |
Cut size sheets |
Describes all unfolded formats from DIN A3 and smaller. Larger formats are referred to as “folio sheets (greater than DIN A3)”. |
D
Degree of whiteness |
The impression of the degrees of paper whiteness gained by an observer. These can be bluish, reddish, greenish or yellowish. The degree of whiteness is a technically measurable quantity. Paper can have various appearances even if it has the same technically measurable degree of whiteness. |
De-inking |
To create a high degree of whiteness from recycling paper, the printing inks have to be removed from the waste paper. They are dissolved by means of soapsuds and compressed air, and then siphoned off. The pulp from waste paper can additionally be bleached. The waste from fillers, coating material and printing inks is disposed of in an environmentally friendly manner. |
Digestion |
In this chemical process, pulp is extracted from wood or perennial plants. Wood chips are solubilised with chemicals under heat and pressure. |
Digital printing |
A printing process which only functions electronically by means of computer technology and needs no conventional preliminary printing stage. The data is transferred to the printer in digital form. |
DIN 6738 |
This standard classifies the longevity of paper and cardboard (40 to 400 g/m2) when stored over a period of years in rooms without air-conditioning. Papers in the durability class (LDK) 24–85 may be described as age-resistant. Papers in LDK 12–80 can be kept for several hundred years when stored and handled carefully; LDK 6–70 indicates a life span of at least 100 years. Papers in LDK 6–40 can be stored in a protected environment for at least 50 years. |
DIN ISO 9706 |
The objective of this international standard is to provide a method of specifying and identifying paper (not cardboard) which, according to current information, shows a high degree of durability and at the same time displays no or only slight changes in the propensities which influence legibility and handling when the paper is kept in a protected environment for a lengthy period of time. |
DIN paper formats |
Deutsche Industrie Normen (German Industrial Standards).
3 basic requirements have to be fulfilled in the standardisation of paper formats:
- The original format = square 1 m2 in size.
- Each neighbouring format must be derived through halving or doubling.
- Each format has to be geometrically similar to the others. From the formula “length : width = SQRT(2) : 1, the dimension 84.1 x 118.9 cm (approx. 10,000 cm2) was derived for the original size DIN A0. The formats derived from this, DIN E … (for paper manufacture products such as envelopes, files, folders etc.) supplement the other formats.
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DIP (De-inked pulp) |
De-inking serves the separation of inking colours from printed waste paper so that the recovered “de-inked” waste paper material can be processed into light and white paper products. The waste paper material evolved after de-inking is described as DIP. |
Dry end |
This part of the paper machine is connected to the wet (press) end. The continuous paper web is fed around several heated rollers with the aid of felt. In this way, water is removed from the web, which causes it to become consolidated. |
Duplex copies |
A sheet copied on both sides. |
Durability classes |
Coated and uncoated paper and cardboard are classified according to durability. These classifications can be found in the DIN 6738 standard, January 1999. |
Dyes |
Are added to the paper pulp to give it continuous coloration. The dyes can also be added when coating (coated paper) and in the size press (surface coloration). The paper is then only coloured on the coated side. |
Last change: 03/08/2007
Contact
Mondi
Uncoated Fine Paper
Kelsenstrasse 7
AT - 1032, Vienna
Tel: +43 (0)1 79013 - 0
Fax: +43 (0)1 79013 - 5065
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