Glossary / D

Dandy roll
A cylinder on a paper machine used to improve formation; also wire roll.

Decor paper
Woodfree, white or single-colour paper, often printed with various patterns, e.g. wood grains. The final product consists of laminated boards or directly coated particle boards used for furniture production.

Defibration
Separation of wood fibres by mechanical and/or chemical means.

Deinkability
Suitability of recovered paper for deinking; depends on paper grade, printing process used, age of paper, and other factors.

Deinked pulp (DIP)
Paper pulp produced by deinking of recovered paper.

Deinking
Removal of printing ink and impurities from recovered paper; to produce recycled fibre pulp with maximum whiteness and purity.

Deinking loss
Unwanted loss of solid material from pulp during deinking (usually 10-40%).

Delignification
The removal of lignin, the material that binds wood fibres together, during the chemical pulping process.

Deposit
Mass of airborne pollutants deposited on a unit area of land or water in a given time, e.g. grams per square metre per year (g/m²/a).

Deresination
Reducing the resin (pitch) content of wood prior to cooking either by storage or using bleaching chemicals to reduce the resin content in pulp.

Digester house
That part of a chemical pulp mill where cooking takes place.

Digital printing
Printing system that cuts out the intermediate stages between prepress (creation of text and images on the computer) and printing. It eliminates the preparation of printings elements, make ready times and the start up procedure required for conventional presses. In addition, presses are only capable of printing the physical image borne by their printings elements, which is identical for the every impression. Digital presses can be personalized for each single run.

Direct cooking
Cooking in which heating is achieved by blowing steam into the cooking liquor.

Dispersion
The separation of a substance into the smallest possible particles using another substance (the medium). Used in papermaking to homogenize pulp properties and remove impurities.

Dissolving pulp
A chemical pulp grade used, for example, in the production of acetate and viscose fibres and cellulose films.

Document paper
Document paper is paper with a high ageing resistance. It is woodfree but may also contain rags or be fully made from rags and is used for documents that have to be preserved for a longer period.

Double coating
Coating of paper or board twice on one or both sides.

Drainage
Formation of a paper or board web on the wire by removing water at the paper machine wet end.

Drawing paper
General term for paper intended to be used for drawing. The quality of normal drawing paper varies greatly, depending upon the intended use. It is almost never contains wood pulp, whilst the finer grades that are intended to be kept for long periods contain a high percentage of rag or are entirely rag papers. The stock is always well sized in order to resist penetration by water–colours. It may often also be sized with starch or animal size and the surface is, to a greater or lesser degree, rough. The best grades are part hand, part machine made on cylinder machines, whilst medium and cheap grades are produced on Fourdrinier machines. Only very high quality paper is made by hand. Grammages ranges from 100 to 400 gsm. Given the intended use, these papers are never watermarked other than with the manufacturer’s mark. Ingres paper is a high quality drawing paper. This is a laid paper made by hand or partly by hand partly by machine. With a coarse, distinctive grain, a grammage of 90–100 gsm and is often in pastel shades. Technical drawing paper, also referred to as tracing paper, is a dense, highly transparent paper with grammages ranging from 30 to 100 gsm.

Dry coating
Coating method in which a binder is applied to the paper surface followed by dry coating pigment.

Dry creping
Creping of a dry paper web.

Dry end
Final part of the paper machine from the drying section onwards.

Dry solids
Mass of dried sample as a percentage of mass of original sample.

Dry strength
Mechanical strength of a dry paper sheet (includes tensile strength, tearing resistance and folding endurance).

Duplex board
Duplex board consists of two layers, mostly made from waste paper pulp. It is used for packaging purposes.