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GLOSSARY

Hardwood
Wood from the angiosperm order of trees. Although generally harder than softwoods, there are examples of hardwoods that are softer than softwoods and vice versa. Hardwoods have more vessel elements and generally shorter fibre length than softwoods. Examples of hardwoods are birch, beech, maple, oak, eucalypt and poplar.


Head box
In a papermaking machine the head box holds the pulp, also called stock, before it is sprayed onto the continuous wire for sheet formation.


Hemicellulose
A group of polysaccharides associated with cellulose in the plant cell wall. They are less crystalline than true cellulose and also shorter and less resistant to hydrolysis.

Hot pressed
Hot pressed papers have been heated, either in a press or by heated rollers, to remove water from the still wet sheet. Hot pressed papers generally have a smoother surface than cold pressed papers.


Hydrogen peroxide
An oxidizing bleach that was first discovered in 1818 by Louis Thenard. Although the chemical itself can be expensive, its ease of use and low plant capital cost outlay have made it a popular pulp bleach. In the shorthand for describing bleaching processes it is represented by the letter ‘P’.


Indanthrene blue
A deep, dark blue dye that is also written as Indanthrone blue. It is made by aminoanthroquinone treated with potassium hydroxide and is known to be very lightfast. It was first manufactured in 1901, and became widely available in the 1950s.


Internal sizing
Internal sizing is when the sizing agent is applied to the pulp from which the sheet will be formed. This process is also called engine sizing.


Jordan refiner
This is another name for a cone refiner.


Kappa number
The kappa number is an indication of residual lignin in a pulp. The kappa number is determined by the amount of potassium permanganate that the pulp will absorb and is used as a measure to determine the amount of bleaching required.


Kaolin
A white clay, composed mainly of kaolinite, an aluminium silicate. It can be added to pulp as a filler, to increase opacity or as component of coating. It is also known as China clay.


Kozo
The Japanese name for the paper mulberry. The bast fibres of the paper mulberry have been used in papermaking for centuries. The fibres are very long and strong meaning that the fibres may be added to a wide variety of other fibre types, and the resulting paper used in a wide variety of uses, from writing, painting, calligraphy, folding screens, umbrellas, sliding doors, toys, lanterns etc.


Kraft Process
Another name for the sulphate process of chemical pulp processing.


Laid paper
Laid paper is made with the distinctive laid and chain lines. Traditionally the laid and chain lines where created in the sheet through the wires on the handmade screen, however today they are recreated through an impression into the wet formed sheet by a dandy roll. A paper without laid and chain lines is known as wove paper.


Laid Lines
In laid paper the laid lines are the thinner lines that run counter to the thicker, more widely spaced, chain lines. A traditional handmade paper mould is a series of fine wires through which the water could drain while the wires would catch the pulp. The laid lines are the thinner wires that are attached to the thicker lines known as chain lines.


Lignin
A series of complex chemical compounds found most commonly in wood as a means of supporting and strengthening. Lignin fills the space between the cell walls, especially in the xylem, and helps binds cells and fibres together. Papers with lignin content are known to darken, become acidic and degrade more quickly than lignin free papers. Rag papers have no or very little lignin and generally last longer.


Linen Finish paper
A sheet that has been given the impression of linen cloth through pressing. The linen cloth impression can be given to the paper by pressing it between linen cloth, between linen covered rollers/belts or having a dandy roller with a linen cloth pattern on it.


Machine coated
Paper that has been coated during its processing through the papermaking machine.


Machine direction
The direction in which the paper pulp runs onto the papermaking web in the papermaking machine. It is also the called the grain direction on the paper.


Machine dried
A drying process in which the paper is dried by passing through heated rollers.


Mechanical Pulp Process
This is pulp produced without chemicals. There are two main methods of producing mechanical pulp: groundwood pulp and thermomechanical pulp. Groundwood pulp is created by feeding wood through metal grinders; if it is created through the use of a refiner it is called refined groundwood pulp. If the grinding takes place at high pressure it is called pressure groundwood. Thermomechanical pulp is created by grinding the wood while it is being steamed at pressure, this reduces the energy needed and results in less damage to the fibres. Mechanical pulping usually requires more energy than chemical pulping. The process does not remove lignin from the pulp so papers produced using this method is prone to high acidity, discolouration and embrittlement. Mechanical pulp paper is often used for the production of newspapers. Mechanical pulp has a pulp yield of over 90%.


Manila hemp
A traditional name for fibre from abaca, a species of banana originated in the Philippines, and which is now grown in the tropics for its fibre.


Mitsumata
A shrub growing in Japan that is used for papermaking. The inner bast bark is used in papermaking.


Modern laid
A laid paper in which there is no shadowing around the chain lines visible through transmitted light. Modern laid paper was developed around 1800 with an improvement in handmade paper mould design, and then the introduction of machine making paper and the dandy roll.


Multi-tonal watermark
This type of watermark incorporates light and shade into its design as opposed to the linear watermarks previously used. It is formed by instead of using wires on the dandy rolls surface it has areas of relief forming the image in the dandy rolls wire surface. T H Saunders exhibited examples of multi-tonal watermarks in 1851. They are often used in security papers, such as in cheques and passports. They are also known as chiaroscuro watermarks or light and shade watermarks.Newsprint
A low cost, non-archival paper that is used for printing newspapers. It is usually composed mainly of mechanical pulp.


Naginata beater
A naginata beater is a Japanese designed beater that uses slightly curved dull blades to beat through the pulp, rather than a dull bladed roller as used in a Hollander or standard beater.


Neutral sulphite pulp
A process in which the lignin is softened, but remains in the pulp during refining. This process involves mild cooking with sodium sulphite combined with sodium carbonate to produce a neutral pH cooking liquor. Since it does not remove the lignin the process is a semi-chemical one and the resulting sheet or board suffers from the same long term acidity and loss of strength as other mechanical processes.