Paper Terminology

The degree to which paper takes up an amount of liquid. Measured by a standard test.

Free from any acid content or any other substances likely to have a detrimental effect on the paper or its longevity. Acid-free paper is paper that if infused in water yields a neutral or basic pH (7 or slightly greater). It can be made from any cellulose fiber as long as the active acid pulp is eliminated during processing. It is also lignin- and sulfur-free. Acid free paper has a longevity of between 500 and 1,000 years depending upon the grade of paper and various environmental effects.

Alpha cellulose is one of three classes of cellulose, has the highest degree of polymerization and is the most stable. The other two classes, known as hemicelluloses are beta cellulose and gamma cellulose. Alpha cellulose is the major component of wood and paper pulp. The pure white, alpha cellulose is insoluble and can be filtered from the solution and washed prior to use in the production of paper or cellulosic polymers. A high percent of alpha cellulose in paper provides a stable, permanent material.

A term loosely used to indicate paper with long lasting qualities, acid free, lignin free, usually with good colour retention. is an especially permanent, durable acid-free paper. Archival paper is meant to be used for reproductions of high legal, historical, or significant value.

The term baryta comes from the chemical compound barite – barium sulphate – which is a naturally occurring, clay-like mineral added to the fibre paper base. It is traditionally applied to a fibre photographic paper base prior to coating with the emulsion layers. It was used to whiten papers, provide reflectivity, and serve as a base for the light sensitive emulsion. The technical benefits of the Baryta layer include a smoother, brighter, whiter, opaque base which helps to achieve greater detail and definition, extended tonal range and excellent archival properties. In addition, Baryta coated fibre papers have a unique look, feel and mild odour which harckens back to the traditional fibre based silver gelatin print papers used by the likes of Ansel Adams, Yoseph Karsh etc.

A general term for thick, stiff paper over a certain weight; on average 250 – 300 gsm.

Paper’s ability to reflect white light. Brightness values are a measure of the reflectivity of paper to light under controlled conditions, on a scale of 0 to 100: most bright papers have brightness values of 75 to 100. Papers with the highest brightness are made by adding fluorescent dyes to increase their reflectivity.

Calcium carbonate (chalk) is often added to paper pulp during the paper making process as a buffering agent. This buffering agent raises the pH level of the paper to the alkaline side of the scale, making it non-acidic, and acts to counter acidic substances or pollution in the environment (such as smog) from impacting the buffered material. Many inkjet papers themselves are buffered for this reason. The Image Permanence Institute now contends that either buffered or non-buffered materials are acceptable for all photographic prints except for dye transfer and cyanotypes.

The volume or thickness of a paper in relation to its weight.

A form of limestone or chalk that occurs naturally in a water supply or has been ground into powder and added to pulp. When used in large amounts it acts as a filler to improve opacity and whiteness. It also serves as a “buffering” agent to protect paper from acidity.

The thickness of a single sheet of paper measured with a micrometer in 1/1000 inch, millimeters or microns. Also and instrument used for such measurements.

The process of pressing paper through rollers (usually of hardened, polished metal) to increase its surface smoothness. Also, “Glazing”.

The basic substance of paper making: the main part of the cell wall of a plant. Only cellulose has the property of forming bonds so essential in papermaking. It is extracted from wood by mechanical or chemical means. Cellulose fibres are not pure enough (except for cotton) to be used directly for paper making but contain varying amounts of other material, including lignin, from which they must be separated before use.

A filler or loading agent used to obtain opacity, or fill or coat the surface of a sheet.

Paper coated with china clay or other filler to give a smooth surface making it suitable for the printing of fine detail.

Chiefly U.S. and Canada. Otherwise, “NOT”or “Not.” Short for ‘Not Hot Pressed.’ One of the three traditional surface finishes of handmade paper between Rough and Hot Pressed produced by pressing between felts.

Is the purest form of cellulose produced in nature and it requires the least amount of processing before it can be used for papermaking. Cotton fibre is obtained either from the shorter fibres attached to the seeds of the cotton plant (cotton linters) or from the longer fibres of cotton fabric (rag).

The removable wooden frame that fits over the mould to contain the pulp. It also helps to keep the hands away from the fragile wet sheet. The inside measurement establishes the size of the handmade sheet. A Western papermaker’s equipment includes two moulds to every deckle so that the process of paper making can be continuously performed. A deckle strap on the paper machine controls the width of the web.

The wavy, feathered or ragged edge on four sides of a sheet of handmade paper caused where the pulp seeps under the deckle frame during formation. Also found on mouldmade papers on the two outside edges of the web.

Resistance of colour to fading.

(Also called Blanket); A rectangular piece of absorbent woven material, usually of wool, cut larger than the paper, onto which newly formed sheets are couched. Various grades exist to give particular surfaces to the wet sheets. For cylinder and some Fourdrinier machines, the felts are sewn together to form a continuous loop.

A finish to the top surface of paper created by the texture of the felt; often with a special weave.

Cellulose-based material derived from plant matter which forms, with water, the basis of a sheet of paper. Papermaking fibres are hollow tune-like structures with walls made up of thread-like ‘fibrils.’

A general term for the various surface textures of papers and boards; Rough, NOT (Cold Pressed) and Hot Pressed are the three traditionally given to handmade paper.

The standard type of machine on which paper is made at high speed in a continuous web. Sheets made in this way are called ‘machinemade’. Largest fourdrinier in the world made in Germany.

A type of sizing obtained from animal tissues which is applied to the surface of paper to make it impervious to water and to aid resistance to bleeding during printing. It also imparts surface strength to watercolour, writing and drawing papers. Gelatine sizing can effect the colour to some degree.

A process used to create a smooth surface finish on paper,typically achieved by running dried sheets through steel rollers or between polished zinc plates or by pressing or friction. Also ‘Calendering.’

The alignment of fibres in a sheet caused by the flow of the web of wet paper in a Fourdrinier machine. Long grain is when fibres run in the machine direction. Short grain in the cross direction.

Grams per Square Meter. Countries outside of North America use GSM to specify this measurement of weight of paper. This measure of the weight of paper is more accurate than poundage because it expresses the weight of 500 sheets of a paper at one square meter. While the pound system is also based upon the weight of 500 sheets (a ream), the size of the ream is specific to a master sheet the size of which can vary considerably. For example, one master sheet can be 22″ x 30 while another is 24″ x 36″.

High alpha cellulose fibre is wood pulp which has been further processed and is considered to have the same longevity as cotton.

One of three traditional surface finishes of handmade paper. Today, this term denotes the smoothest surface, achieved by passing sheets between heavy metal boards or rollers (occasionally heated).

Very thin, high-quality, opaque rag paper often used for printing bibles.

A top layer of  microporous silica which is coated on the surface of paper or other substrate. It is prepared to receive inks and draw them in almost instantaneously so that the surface of the print appears dry to the touch. With the use of an electron microscope one can see that the layer resembles Swiss cheese. Ink is wicked into the open areas beneath the surface.

Is used as a general term for Japanese paper made from the inner bark of mulberry trees, such as the paper mulberry Broussonetia papyrifera and bast paper fibers harvested from that plant. Kozo papers are often used for backing when Asian scrolls are relined. Kozo is an important paper fiber in traditional Japanese, Korean, and Chinese hand-papermaking. The inner bark requires little chemical intervention to create high quality, long fibers that are low in lignin. The long fiber length and high percentage of alpha cellulose impart strength to Kozo papers.

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The substance found mainly in woody plants which rejects water and resists bonding and therefore must be removed from the fibres before the papermaking process begins. If it is not removed from the wood pulp, the resulting paper is subject to rapid deterioration.

Tiny fibres that are left behind on the cotton seed after ginning removes the longer cotton fibres from the seed. The seeds are then spit out in to huge mountainous piles, where they are later scooped up and shaved. The shavings are called linter which is just the finest, silky fiber of less than a small fraction of an inch. But in the production of paper, it is without equal.

Digital top layer coating on inkjet media which is prepared to receive inks by sucking them in almost immediately so that they appear to be dry to the touch. See: Inkjet Coating

Amount of moisture in paper, expressed as a percentage of weight.

A substance used to fix a dye to a fibre.

The basic tool of a hand papermaking, consisting of a flat frame to which a mesh of brass wires or a woven cloth is fixed.

Short for ‘Not Hot Pressed’. Chiefly British. One of the three traditional surface finishes of handmade paper (between Rough and Hot Pressed) produced by pressing between felts. See ‘Cold Pressed’.

The quality of opaqueness in a paper, produced by adding ingredients such as china clay, calcium carbonate or titanium dioxide (opacifiers). Governs the degree of ‘show-through’ of printing on the reverse side of the sheet or on sheets underneath.

Optical brighteners are chemical additives which most paper manufacturers add to paper in order to help it look “whiter” or “brighter.” They can cause invisible ultraviolet light to re-emit in the blue spectrum – or “fluoresce” at a point which is barely within our ability to see. We see the result as a brighter, blue-ish white. These are also called optical brightening agents (OBA).

A phenomenon where the humecitant or anti-drying agents in inks come out of the print and are deposited on a surface such as the glass in front of a framed print.

The longevity of a print prior to any signs of deterioration. The major factors determining your print longevity are your material choices for inkjet paper, inks and possibly coatings combined with the actual environmental conditions, ie., the light intensity on display, the temperature on display or in storage, and the relative humidity on display or in storage.

The pH value describes the acidity or alkalinity . It is a measure of the availability of free hydrogen ions. Zero pH is very acid and 14 pH is very alkaline. A pH of 7 represents the balance between acid and alkaline components and is neutral.

Paper weight in the US is stated in lbs. and is determined by weighing 500 sheets (a ream) in the basis size of a particular paper.

Formerly the principal raw material used in the papermaking process. The term ‘rag’ or ‘all-rag’ properly describes a sheet made entirely from used textiles (usually cotton) as the basis for the pulp. Today, however, more commonly it is a misnomer and indicates that the paper has been produced from cotton linters. The term ‘rag content’ describes the amount of cotton fibre relative to the total amount of material used in the pulp.

500 sheets (a ream) in the basis size of a particular paper. The basis weight is based upon the master sheet for a given paper. The physical dimensions of that master sheet varies between various papers.

A commonly used internal sizing agent; occasionally also used for surface sizing. Introduced around the early 1800’s it is acidic in nature and detrimental to the permanence of paper. It requires the addition of alum for precipitation onto the fibres.

One of the three traditional surface finishes of handmade paper. A rough surface properly obtained by loft-drying in natural air.

(1) A non-cellulose material which is added to paper to increase its resistance to the penetration of water (inks, paints, etc.). Also increases surface strength. (2) The dimensions of a sheet of paper.

A solution or the process of applying such solution to make paper moisture-resistant to varying degrees.

Deep blue pieces of glass pulverized and used as a colouring agent.

Essentially the surface flatness of a paper. It is not the same as ‘gloss’ which is an optical property and is not related to porosity.

The weight or grammage of a sheet of paper expressed in gsm or lbs per ream.

The surface detail or finish of a paper which can be a natural result of the quality of the pulp, processing or drying, or a contrived impression.

Describes a roughness in the surface character, at its extreme in sandpaper, which holds on to grains of colour; texture that grabs a drawing pigment.

At one time, it was believed that photographs stored in buffered enclosures might be adversely affected by buffering. This is no longer believed to be true except for a couple of specific types of photographs. With dye transfer prints and cyanotypes, unbuffered enclosures should be used. The image substance of both these print types can be harmed by alkalinity.

(1) The prepared inner side of calfskin or kid skin. (2) A paper surface which imitates true vellum, notably any matt wove type. Often used to describe mouldmade and Japanese papers.

Is traditional Japanese paper. The word “washi” comes from wa meaning ‘Japanese’ and shi meaning ‘paper’. The term is used to describe paper that uses local fiber, processed by hand and made in the traditional manner. Washi is made using fibers from the inner bark of the gampi tree, the mitsumata shrub (Edgeworthia chrysantha), or the paper mulberry (kōzo) bush. Washi is generally tougher than ordinary paper made from wood pulp, and is used in many traditional arts.  Several kinds of washi, referred to collectively as Japanese tissue, are used in the conservation and mending of books.

A translucent design in a sheet of paper that can be viewed as a paler area when held up to the light. Typically, watermarks are linear, formed in wire. In shadow or chiaroscuro watermarks, the image appears tonally.