Calcium carbonate has been used historically in hand papermaking in the form of chalk, or ground sea shells, to increase the brightness of the sheet. In more recent times it has been used in its purer chemical form as an alkaline filler, usually between 10% and 20%, or coating agent in paper. It is largely replacing kaolin and other fillers as it is generally cheaper, more archival , creates stronger paper, retains brightness for longer, more easily used as a substitute for expensive fibres, and since it cannot be used in a papermaking machine working at below pH 6.5 has increased in usage with the increase in alkaline papermaking. It is used as either Ground Calcium Carbonate, GCC, or Precipitate Calcium Carbonate, PCC. In 1986 a PCC satellite plant was introduced in the USA. Calcium carbonate is not suitable for use in acid paper making or papers with a high lignin content.
A chlorine based bleach, Ca(ClO)², invented in 1799 by Charles Tennant in Glasgow, Scotland. It was the dominant form of bleaching until the introduction of gaseous chlorine and dioxide bleaches about 150 years later.
Calendering is a step in the modern papermaking process where, towards the end of the papermaking machine, the sheet is smoothed by passing it through hard rollers. The rollers can be metal, or of a softer polymer depending on the finish required. They can also be embossed with a texture to achieve a particular surface finish, for example linen finish paper. Paper that has been supercalendered has passed through alternating metal and fibre covered rollers and is known for its highly glazed surface that is used in publishing. Paper can also be ‘platen calendered’ as a separate processing step; in this case sheets are cut and pressed between metal plates.
A group of proteins found in milk, usually derived from cow milk. It has been used as a glue, or binder, in coating formulation. A coating formulation made of a combination of casein, or animal glue, and kaolin was introduced in 1807. Since then it has been used as a coating binder.
A modified positively charged starch used in the wet end of a papermaking machine to increase the interfibre and fibre to filler and size bonding. The use of cationic starches increases sheet strength, sizing, filler and fines retention
Cellulose fibres are the basis of the pulp from which paper is made. Cellulose is a long chained linear polysaccharide that plays an important structural role in the cell wall of plants. It was first discovered in 1838 by Anselme Payen, and the structure was discovered in 1920. The formation of hydrogen bonding between oxygen atoms in different hydroxyl groups holds the chains of cellulose firmly together giving tensile strength to the cell wall, and then later to paper. Cellulose breaks down through hydrolysis into smaller polysaccharides or glucose, this process is sped up in an acidic environment. Cotton is composed of 90% cellulose, making it one of the purest naturally occurring forms.
In a laid paper the chain lines are the thicker, less frequent, lines in the paper sheet. 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 chain lines are the thicker wires that the many finer parallel running wires were attached to. The finer lines created by the finer wires are referred to as laid lines.
A pulping process in which the wood chips are pretreated with chemicals to soften the lignin. Unlike chemical process the aim is not to dissolve or break apart the lignin and remove it – ChemiMechanical pulping aims to only loosen and soften it. Common types of ChemiMechanical pulp are hot sulphite, using sodium hydroxide and sodium sulphite; and cold soda, using sodium hydroxide. It is often used on hardwoods, and has a pulp yield of 80-90%. It is often referred to as CMP.
A process in which the lignin is softened with sodium sulphite or sodium hydroxide, and then mechanically pulped under heat and pressure. It is often used with hardwoods and has 80-90% pulp yield. It is often referred to as CTMP.
Another name for Kaolin.
Chlorine dioxide bleaching
An oxidizing bleach, referred to as (D) that was usually done in sequence with alkali washing of the pulp. As it reacts selectively to lignin and wood resins without effecting cellulose under ideal conditions it was widely used, especially in the five stage CEDED bleaching process. Chlorine dioxide bleaching was first used in Canada in 1946. Elemental chlorine free bleaching, ECF, still uses chlorine dioxide bleaching, while total chlorine free bleaching, TCF, does not. In 2005 85% of world chemical pulp was bleached with chlorine dioxide.
A deep yellow pigment that was first encountered in its natural form of crocoite in 1766 in mines in the Ural Mountains of Russia. It was synthesized in the laboratory by mixing a solution of lead nitrate and potassium chromate, and then filtering off the lead chromate solution. It has the chemical formula of PbCrO4. It was first created by Louis Vauquelin in 1797, and its first recorded use as a colour in English is in 1818. Since it darken with air exposure, and contains toxic heavy metals it is currently rarely used.
Coal tar dye
Aniline synthetic dyes developed between 1834 and 1843 by the chemists Otto Unverdorben, Friedlieb Runge, Carl Fritzsche, Nikolay Zinin and August von Hofmann. In 1856 William Perkins discovered mauveine and started the industrial production of synthetic dyes.
A paper that has had its surface treated with a glue, such as casein; clay, pigment and adhesive mixture is used to improve smoothness and gloss, and reduce ink absorbency. Kaolin and calcium carbonate are frequently used in combination with organic or inorganic binders as coating agents to improve printing quality of papers.
Cold pressed paper has been air dried and then pressed in an unheated hydraulic press or through cold calendering. They generally have more surface texture than hot pressed papers.
A low grade bond or offset paper.
A type of fibre refiner that may or may not be used in conjunction with a standard, Hollander beater. It consists of a conical rotating plug and the matching shell in which it is fitted. Both the plug and shell are covered with knives or bars, and as the pulp is fed through the rotating plug the fibres are pulled apart. It was first invented by Joseph Jordan in 1860. It is also called a Jordan refiner.
Also known as the continuous web, it was originally a woven metal mesh onto which the pulp is sprayed, although currently it may be a plastic mesh.
A plant whose soft fluffy fibres around the seed have been used for papermaking for centuries. This protective soft, fibrous barrier around the seed, known as the boll, is almost pure cellulose. Paper made from cotton is known as rag paper, or cotton fibre content paper, and is generally high quality due to the absence of lignin from cotton.
Cotton linters are the short fibres that adhere to the cotton seed after the ginning process.
Cotton Fibre Content Paper
Paper made of at least 25% cotton derived cellulose.
The countermark is a watermark that gives the name of the manufacturer, their initials, mill or place of manufacture of the sheet. Often when one side of the sheet would contain an image this was referred to as the ‘watermark’ and the other mark on the opposite side of the sheet giving the name of the manufacturer, initials, place of manufacture etc being called the ‘countermark’. It is formed with raised wires in the mould in the same way as a standard design watermark. Not all sheets will contain both a ‘watermark’ and a ‘countermark’. Countermarks started to be used in the 17th century in England and earlier in France.
A fold or cut running against the grain direction of a sheet.
A smaller sheet of business paper that has been cut down from a larger sheet with a guillotine. Sizes are measured in inches and are 8″ x 10″, 8½” x 11″, or 8½” x 14″.
Cylinder mould machine
Developed in 1809 by John Dickinson in England, the cylinder mould machine differs from the standard Fourdrinier machine in that the instead of the pulp slurry being poured onto the wire, a wire covered cylinder is dipped into the vat of pulp slurry. Unlike the Fourdrinier machine the cylinder mould produces genuine watermarks that are wires woven into the cylinder mould, and can produce paper with four deckled edges by having thicker wires to mark the sheet size that can be torn through to give a deckled edge. It can also produce rolls of paper. Although they can be slower than other machines they allow a strong sheet, greater dimensional stability through a thicker cellulose fibre web, and true watermarks on the wire side. It is also called a mould made machine.
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