Acidity : acids destroy paper, they weaken them by forming spots. For this reason CLAIREFONTAINE makes its paper using only pure water which protects it from outside sources of acidity and by adding neutral PH (calcium carbonate). The acidity of a paper is measured by its pH level. A pH7 is called neutral pH. The alkaline reserve increases the pH to about 8,5.

Additives : are introduced into paper (writing and printing). Their purpose is to increase the water resistance, the opacity and dimensional stability. They reduce the mechanical resistance of the paper. Kaolin is the most frequently used additive. Others are talc and titanium oxide.

Basis weight  : unit mass of paper or card. It is expressed in grams per square meter (ex: 80g/m2) A 300g paper weighs 300g per m2. The higher the figure the more rigid the paper.

Bound 4 sides : (or stretched): this is the name given to paper where the sheets and gummed together on all sides to stretch them and prevent them from warping. These blocks are very useful for outdoor work, especially for very wet techniques.

Bristol : defines the smooth paper made by layering or laminating papers together to the desired thickness as originally made in Bristol. The best are well sized and closed formation.

Calender : At the end of the flat table fabrication line, a calender, a set of cast rollers, flattens and smoothes the surface of the paper

Cellulose : the fibres which make up paper pulp, mostly from wood, after elimination of the lignin.

Coated : paper which is coated, generally with kaolin (but sometimes calcium carbonate, barium oxide), for finer and more precise work. The surface can be shiny or matte. It offers the possibility of correcting or scraping for drawing

Cotton : (linters) pre-processed pulp, cotton or wood, purchased in sheet form. Linters are the short fibres left on the seed after the long fibres have been removed for use in textile. Its price limits is use to the best quality papers.

Cylinder/hand mould  : paper obtained from pulp recuperated from a vat using a type of screen or belt the size of the paper, called the “form”. After drying, the sheets are compressed between felt and then finally air-dried.
Round form: industrial method for obtaining continuous formed papers

Deckle edges (fringed edges) : when paper was hand-made, the diluted pulp was placed on a screen (called web) to drain off the water. The natural edges of the paper were left irregular and uncut. Today the process is similar but the screen is fixed on a round mould from where comes the expression “moulded edges.”

Deep-dyed : colorants can be introduced into the pulp or added to the surfaces in the last stages of fabrication. The difference can be seen when the paper is torn: deep-dyed paper has the same colour both on the surface and inside

Double backed : name given to rigid material obtained by gluing one or two sheets of paper on card.

Featherweight paper  : non-calendared paper made from pure pulp

Fungicide : treatment to prevent mould caused by humidity

Glazed : describes the aspect of a smooth untextured matt paper (resembles satin)

Grain : soft, fine, medium, rough, the grain is the imprint left on paper from contact with the felts of the paper machines

Hand : this expression is used to describe the mass volume, not the density of the paper. To calculate the hand: thickness in microns/ gram weight in g/m2

Hand : 25 sheets

Jets : characterizes the thickness of papers or cards required for a thick double backed card

Kaolin : A very pure form of white clay used as an additive in the pulp or in the mix used to cover coated papers

Laid : paper with a continuous watermark consisting of very close parallel lines, generally associated with spaced lines (chain lines) at right angles to these. The first papers were all laid. Ingres is one of the recognised standards of laid paper, introduced by the painter Ingres

Mounting : from (a strong paste) – mount a painted canvass on a wall, a wooden board, a stronger canvas. Paper can also be mounted on canvas

Metamerism : meaning two colours which seem identical under a certain light and different under another

Optical Whiteners : Optical whiteners enhance the whiteness and brightness of the page. However the brighteners wear out and the paper quickly yellows and alters transparent colours. Only natural bleaching of the pulp can guarantee an inert white

Permanence : chemical stability of paper over a long period

PH neutral  : describes a paper made without acid and which will preserve both the support and the brightness of colours

Rag : paper made from pulp contains some pure rag. The amount of rag used to create “rag” papers varies from one country to another.

Ream : 500 sheets (20 hands)

Sheet formation  : the structural aspect of a sheet of paper observed when holding it up to the light. This aspect can be uniform or split, it can also be “cloudy” if the fibres are not distributed evenly. A look through (sheet formation)is the uniformity of the formation of the paper, the regularity of distribution of the fibres in the sheet. A good sheet formation , increases its opacity and improves its performance during printing.

Sizing : addition of products either to the pulp or to the paper’s surface in order to limit the penetration of watery liquids such as writing ink, watercolours and gouache.
The size press applies starch or gelatine on to the sheet which makes it waterproof and ensures its stability.

Vellum : cotton-based paper which appeared around 1770, its name comes from the Latin velum (calf-skin), which enabled the confection of the finest parchment papers. It is a smooth or grain paper. CLAIREFONTAINE makes vellums renowned worldwide for their softness

Watermarks : the printing of a design or a text during the papermaking process into the thickness of the paper. It is a design engraved in the pulp with a metal wire fixed to the belt of the machine. It can be seen by holding it up to the light as the paper is thinner at this spot.
In the cast of flat table fabrication the watermark is made when the papers passes under a watermark cylinder before being dried.
The watermark designs were originally the names of paper formats: grape= bunch of grapes.
Other types of marks exist:
Engraving: this is done by a raised engraved wheel which leaves a continuous engraved imprint along the edge of the paper while still wet.
Depressed stamping or embossing: dry marking on paper after fabrication.

Wet strength  : A chemically treated paper strong enough to withstand tear, rupture or falling apart when saturated with water. CLAIREFONTAINE paper absorbs very little water. The paper does not alter or deform and colours remain on the surface as the water does not penetrate the pulp.
Reworking is easy. Colours can easily be wiped off if wished.
Drying is rapid and regular (uniformity of paper) leaving the pigment on the surface which enhances the luminosity and vividness of colours.

Wood card  : a card usually made from mechanical pulp. It is used only when not visible (framing)