Production-methods: (unfortunately not yet a spanish version available)
Handmade paper is produced in much the same way as in the past, scooping an amount of pulp from the vat onto a mould by hand, with variations in different parts of the world adapted to suit local conditions. Only a few papermills survived where paper is still being made this way. The initial step involves the preparation of the pulp: the raw material must first be softened and reduced to the state of fibres, a process effected by the action of beating or maceration whilst suspended in water. In the next step these treted fibres (the pulp) are poured into a trough containing a large amount of water in an approximate ratio of 90% water to 10% fibres. A sheet of paper is produced by various methods, all of which allow a wet layer of pulp to bo formed to the mould.
Today most paper used in printmaking is mouldmade. To see how it works, check out "Arches" or other papermills on this site. The paper made on a cylinder-mould machine closely resembles the handmade product. The initial pulp preparation is similar right up until the formation of the sheet, when the machine takes the space of the vatman, coucher and layer.
Machine made paper.
Almost all "commercial" papers are machine made on a Fourdrinier-machine. The production speed is much higher then the mould-made system. Some papermills use a Fourdrinier-machine also for the production of printmaking paper, but at a much lower speed. (Papermill Schut in Holland). On a classic Fourdrinier machine, processing starts at an adjustable "box" which is continuously fed with purified, highly diluted pulp. A flat, endless, plastic wire mesh shakes sideways as the pulp is discharged onto it in order to achieve a degree of lateral cross-linking of fibres. Controlled drainage is achieved by means of scrapers and wet air suction boxes. As the layer of wet fibres which will become paper arrives in the middle of the machine, the surface of this web is smoothed by a "dandy" roll and an impressed watermark is applied if required. At the end of the wire section, the web is transferred to wet presses where more water is pressed out.
What is in paper?:
Raw unprocessed fibres
Raw fibres are classified according to their location in the plant. Bast (inner bark) fibres, such as flax, hemp and kozo are some of the longest available for making paper. Leaf fibres, from plants such as sisal and yucca, are shorter. Seed-hair fibres, attached to the covering around the seeds of certain plants, notably kapok and cotton, are shorter still. The length of the fibers plays an important role in the strength of the paper.
Paper has traditionally been made from many discarded materials, such as old hemp ropes, worn-out clothes, and sacks. Many papers are described as "rag" but very few now are truly so, in the sense of being actually made from rags. For many hundreds of years, collected old cotton and linen rags were the basis for Western papermaking, and depending on their origins they often gave a colour to the resulting sheet. Today, rags - both used and in the form of new material from the textile industry - are most commonly employed in India and in a number of small mills in Europe and the U.S.; individual sheets can be found made from such miscellaneous fabrics as blue jeans, indigo-dyed work clothes or red wool socks. Fibers made from real rags are much longer then the original fibres where the textile was made from. That is the reason that real cotton based "rag"paper is stronger then paper made from cotton fibres.
Already processed fibres, cooked or partially beaten or in the form of ready-to-use pulps, are sold today in dry, compressed sheet form.
Wood is by far the most common source of fibre for machinemade paper; it is hardly ever used for handmade papers. The wood fibres have to be refined, either by mechanical extraction or a chemical process, to ruduce it to cellulose, the material to make "woodfree" paper. Almost pure cellulose is called "High Alpha Cellulose" .
Additives to the paper during making:
Cellulose fibres are water-loving by nature. Sizing is a non-cellulose material which is added to the paper to increase its resisitance to the penetration of water (inks, paints, etc.) gelatine size - only - also increases the surface strength. With internal sizing, the sizing material is added to the papermaking fibre in its wet state prior to the formation of the sheet; the most common material for this method is rosin. For artrists' papers however, synthetic sizing materials are used, to avoid yellowing. ("Aquapel")
This is a form of limestone or chalk that occurs naturally in a water supply or has been ground into a powder and added to the pulp. When used in larger amounts, it acts as a filler to improve opacity and whiteness. It also serves as a "buffering" agent or alkaline reserve to prtotect the paper in the future from any acidity that may be present in the atmosphere. (="acid free")
China clay (kaolin)
This is a very fine white powder that can be added to the pulp as a filler to reduce shrinkage. When used as a coating agent, it leaves a smoother surface (making the sheet suitable for fine half-tone reproduction)
whiteners, agents to keep the fibres from entangling into clumps, etc.
Characteristics of paper:
Wove or Laid.
Handmade paper was always formed on "laid" moulds. These terms refer to the two types of mesh covering the mould, each of which gives a distinctive character to the sheet. The wove surface was developed around 1755, in England, when the printer John Baskerville asked the papermaker Lames Whatman to make a different type of sheet; Baskerville had designed a typeface with fine serifs and wanted a paper with an exceptionally smooth surface to print onto.
Today, the term "antique" is applied to a surface which imitates the laid character of an old sheet; "mediaeval" indicates that the laid lines are very pronounced or irregular.
This refers to the degree to which a sheet of paper changes shape, which depends on beating, climate and atmosphere. When a sheet of paper is subject to a moist atmosphere (or is purposely dampened), the fibres absorb water and swell, and when they dry (or if heat is applied), they contract. This takes place over the whole area when it is exposed, or simply at the edges if the sheets are stacked. Paper made from highly beaten (or hydrated) puplp is usually stronger but also less dimensionally stable. The degree of internal bonding between fibres and the density mean that changes in water content have a greater combined affect on the expansion and contraction of the paper. (This effect is more pronounced in heat-dried than air-dried sheets.) Papers made from less hydrated pulp tend to be less strong because fewer bonds are formed between fibres, but as they are less dense each fibre has more freedom to move, making the dimensional stabiliy greater.
The "grain"of a paper refers to the alignment of the fibres within the sheet. The majority of handmade papers have little grain direction and are described as "roughshake", a term used to indicate that the fibres are distributed at random. This characteristic is a distinctive asset, allowing them to remain stable and strong in variable conditions. Grain is noticeable in papers that are not handmade. On a papermaking machine, the fibres tend to align themselves in the direction in which the web is travelling; the grain direction or machine direction of the paper. At the end of the process the web os paper is cut into rectangular sheets, either parallel to or at right angles to the machine direction. Sheets whose long dimension is parallel to the machine direction are called "long grain" those cut across are called "short grain". The grain in cylinder-mould and Fourdrinier grades has a number of consequences: * Paper tears more easily along the grain direction than across it. * Paper folds more readily along the grain than across it; but folding endurance is greatest across the grain. * When paper absorbs or gives off moisture with changes in atmospheric humidity, it expands or contracts more across the grain than along it.
The introduction of watermarking in Europe is almost certainly due to the Italian papermakers at Fabriano. The watermarking process is a feature of Western papers. Traditionally, a design is fromed out of copper wire and attached to the flat surface mesh of the mould. Where the device is attached, a raised surface occurs. Because the quantity of pulp is less over this raised parts, it appears as a slightly thinner area in the finished sheet.
The deckle is the removable frame that fits onto the papermaker's mould. It determines the edge of the sheet and ensures that it is of consistent thickness during the making. The deckle edge occurs naturally on all four sides of a handmade sheet. In past ages, it was considered a defect and trimmed away for the most part; during the 19th century, however, when machinemade paper entered the arena, the deckle edge was elevated and became a snobbish symbol of a handmade product. Deckle "straps" run down the parallel edges of the web on cylinder-mould and Fourdrinier machines creating two natural deckle edges. They are often trimmed off machinemade paper. In mouldmade sheets, these "true" deckle edges usually remain; the other two imitation deckle edges or "soft" edges are made when the paper in torn in sheets.
Surface finish or texture.
Rough (with a capital R). describes the natural surface of a handmade sheet that is air-dried, without any smoothing or pressing. In mouldmade papers, the Rough surface is made by using a rough felt. Other terms that are used for this surface include coarse, antique, felt and irrtegular.
NOT. Written in capitals or sometimes as "Not", this term is short for "Not Hot Pressed". It describes a surface which is the result of parting and re-pressing handmade sheets without any intermediary felts or boards. The finish is slightly textured, between Rough and Hot Pressed (H.P.)
Hot Pressed. (H.P.) Handmade paper with a smooth finish is described as "Hot Pressed" or H.P. The term os not strictly accurate, for papermakers achieve this particular finish in a variety of ways: the sheets may indeed be pressed between heated glazing rollers, but they may also be passed through cold, higly polished metal rollers with pressure; hitorically, the surface was obtained by polishing with a smooth hard object such as an agate or other stone.
Felt side and wire side.
The side of the paper that remains in contact with the wire mesh of any papermaking mould or wire during its manufacture is called the "wire side". The opposite surface is called the "felt side". The wire side can show the texture of the wire mesh, while the felt side often has a less mechanical, more random texture. In mould- and machinemade papers, the bottom of the web closest to the wire may be more porous than the top or felt side. Thus the paper can be said to be "two-sided" The wire side is more open, contains less size, has longer fibres and a more pronounced grain. The felt side, can have a closer formation and less grain because of better crossing of the fibres, and is usually better for printing. Some papers (often mouldmade) are made deliberately with two distinct surfaces to provide choice for the artist.