Drawing Defined:
Drawing is one way of making an image: it is the process of making marks on a surface by applying pressure from or moving a tool on the surface. These marks may represent what the artist sees when drawing, a remembered or imagined scene or abstraction, or, in the case of automatic drawing, may have much to do with the automatic motion of the artist's hand across the paper (or other surface). (In the process of entoptic graphomania, in which dots are made at the sites of impurities or shifts in colour in a blank sheet of paper, and lines are then made between the dots, superficially speaking the subject of the drawing is the paper itself.) The main techniques used in drawing are: line drawing, hatching, crosshatching, random hatching, scribbling, stippling, and blending.

Common drawing tools are pencils, chalk, charcoal, crayons, pastels, and pen and ink. Many drawing materials are not water or oil based and are applied dry, without any preparation. Water-based drawing media (e.g., "watercolor pencils") exist, which can be drawn with like ordinary pencils, then moistened with a wet brush to get various effects. There are also oil-based pastels and wax-based crayons. Very rarely, artists have drawn with (usually decoded) invisible ink.

One thing that differentiates drawing from painting is that in drawing, an artist uses pure colors and cannot mix them before application. The appearance of mixed colors in some colored pencil drawings is not truly mixing but formed by blending or overlaying pure colors. (In painting, new colors are commonly created by mixing.) When shading and blending is needed, the artist can employ a combination of a tortillon blending stump, chamois or soft tissue, and a specialized putty-rubber eraser.

The colors of drawing media can mix on the surface because of direct chemical interaction. More usually, the mixing is optical rather than chemical: colors are overlaid (also known as glazing) on previous layers so that light reflected from below the surface comes through, or color strokes are close enough that the eye "mixes" them.

Some artists have started referring to pastel and colored-pencil compositions as "paintings". In nineteenth century usage, "drawing" also encompassed watercolor.
Drawing may also be done on a computer. Computer illustration makes use of programs such as Paint, Adobe Photoshop, Pixia, and more, see for example computer illustrations by Peter Welleman. Digital art is fast becoming one of the most popular means of illustration.

Drawing media
The medium is the means by which ink, pigment, or color are delivered onto the drawing surface. Some of the examples include:

• Pencil -
  A couple of very simple pencilsA pencil is a handheld instrument used to write and draw, usually on paper. The writing is done with graphite (except for colored pencils), which is typically covered by a wooden sheath. Pencils may also have an eraser or "rubber" attached to one end. The pencil differs from most pens (other than erasable pens) in that erasing is possible.
  
• History
  The prototypical pencil may have been the ancient Roman stylus, which was a thin metal stick used for scratching on papyrus, often made of lead. The word pencil comes from the Latin word penicillus which means "little tail".
  In 1564, an enormous deposit of graphite was discovered at the site of Seathwaite Fell near Borrowdale, Cumbria, England. The locals found that it was very useful for marking sheep. This particular deposit of graphite was extremely pure and solid and it could easily be sawed into sticks. This was and remains the only deposit of graphite ever found in this solid form. Chemistry was in its infancy and the substance was thought to be a form of lead. Consequently it was called plumbago (Latin for "acts like lead"). The black core of pencils is still called "lead", even though it does not contain the element lead.
  The value of plumbago was soon realised to be enormous, mainly because it could be used to line the moulds for cannon balls, and the mines were taken over by the Crown and guarded. Graphite had to be smuggled out for use in pencils. Because the plumbago was soft, it required some form of case. Plumbago sticks were at first wrapped in string or in sheepskin for stability. The news of the usefulness of these early pencils spread far and wide, attracting the attentions of artists all over the known world. It was the Italians that first thought of wooden holders, at first by hollowing out a stick of juniper wood. Shortly thereafter, a superior technique was discovered: two wooden halves were carved, a plumbago stick inserted, and the two halves then glued together -- essentially the same method that is in use to this day.
  Although deposits of graphite had been found in other parts of the world, they were not of the same purity and quality as the Borrowdale find, and had to be crushed to remove the impurities, leaving only graphite powder. England continued to enjoy a monopoly on the production of pencils until a method of reconstituting the graphite powder was found. The distinctively square English pencils continued to be made with sticks cut from natural graphite into the 1860s. Today, the town of Keswick, near the original findings of block graphite, has a pencil museum.
  The first attempt to manufacture graphite sticks from powdered graphite was in Nuremberg, Germany in 1662. They used a mixture of graphite, sulfur and antimony. Though usable they were inferior to the English pencils.
  English and German pencils were not available to the French during the Napoleonic wars. It took efforts of an officer in Napoleon’s army to change this. In 1795 Nicholas Jacques Conté discovered a method of mixing powdered graphite with clay and forming the mixture into rods which were then fired in a kiln. By varying the ratio of graphite to clay, the hardness of the graphite rod could also be varied (the more clay, the harder the pencil, and the lighter the color of the mark). This method of manufacture remains in use today.
  Manufacture
  Today, pencils are made industrially by mixing finely ground graphite and clay powders, adding water, forming long spaghetti-like strings, and firing them in a kiln. The resulting strings are dipped in oil or molten wax which seeps into the tiny holes of the material, resulting in smoother writing. A juniper or incense-cedar plank with several long parallel grooves is cut, and the graphite/clay strings inserted. Another grooved plank is glued on top, and the whole thing is then cut into individual pencils, which are then varnished or painted.
• Hardness Scales
  Many pencils, particularly those used by artists, are labelled on the European system using a scale from "H" (for hardness) to "B" (for blackness), as well as "F" (for fine point). The standard writing pencil is "HB." However, artist's pencils can vary widely in order to provide a range of marks for different visual effects on the page. A set of art pencils ranging from a very hard, light-marking pencil to a very soft, black-marking pencil usually ranges from hardest to softest as follows:
  9H 8H 7H 6H 5H 4H 3H 2H H F HB B 2B 3B 4B 5B 6B 7B 8B 9B The American system, using numbers only, developed simultaneously with the following approximate equivalents to the European system.
  #1 = B
  #2 = HB -- most common
  #21⁄2 = F -- also seen as 2-4/8, 2.5, 2 5/10 due to patent issues
  #3 = H
  #4 = 2H
• Pencils in Space
  A story in circulation since the 1970s tells of NASA spending large sums of money, typically in the millions of dollars, to develop an instrument that would write in space a (space pen). This task is not as simple as it seems, for standard ballpoint pens require gravity in order to function. The typical punch line is that either someone sends NASA a pencil, or that the Russians used pencils.
  While humorous, it is not true (See Snopes for details). There are drawbacks to using pencils in space. The act of writing would cause graphite dust to come free from the lead and float about the cabin. From there it could become a health risk by being inhaled by the astronauts, clog filters in the ventilation system, or even cause short-circuits by getting into switches and other electrical equipment.
  
• Miscellanea
  The pencil is a common cause of puncture injuries in young children. The tip of the lead may leave a grey mark inside the skin for years. This led to the old-wife's tale that the lead bits could be passed through the blood vessels into the brain, causing retardation in those with such an wound. Of course, pencil lead is graphite and does not contain the element lead, so it is not poisonous. The horror movie House on Haunted Hill depicts a man being stabbed through the neck by a dozen pencils.
  
  • chalk - mineral of calcium carbonate, similar in composition to limestone, but softer. It is characteristically a marine formation and sometimes occurs in great thickness; the chief constituents of these chalk deposits are the shells of minute animals called foraminiferans. Chalk has been laid down in all periods of geologic time, but most of the best-known deposits, e.g., the cliffs of the English Channel, date from the Cretaceous period. Chalk is used in the manufacture of putty, plaster, cement, quicklime, mortar, and rubber goods and also for blackboard chalk. Harder forms are used as building stones. Poor soils containing an excessive proportion of clay are frequently improved and sweetened by mixing chalk into them. **
  • charcoal
  • colored pencil
  • Conté - Conté pastels, also known as Conté sticks, are hard artists' chalks in a variety of colours. They are harder than pastels and contain a greater pigment density; they are square in cross-section.
  They are used for drawing, generally on a rough paper that holds pigment grains well. They can also be used on prepared primed canvasses for underdrawing for a painting. Their square profile makes them more suitable for detailed, hatched work; as opposed to the bolder 'painterly' drawing style demanded by soft pastels.
  • crayon -
  • graphite
  • ink
  • marker
  • pastel - artists' medium of chalk and pigment, tempered with weak gum water and usually molded in the form of sticks; also a work done in this medium. Pastel was in use in Italy in the 15th cent. and is doubtless much older. It was introduced into 18th-century France by the Venetian artist Rosalba Carriera. The medium was then used by such masters as Maurice Quentin de La Tour and Vigée-Lebrun, and in the 19th cent. by Degas, Manet, Toulouse-Lautrec, Whistler, and Cassatt. In the 20th cent. Matisse was a master of pastel. Pastels are often classified as paintings, although the medium lends itself to the more direct and spontaneous approach of drawing. **
  • pen and ink - Pen and ink refers to a technique of drawing or writing, in which colored (this includes black) ink is applied to paper using a pen or other stylus. It may be used as a medium for sketches, or for finished works of art. Pen and ink also lends itself to fine writing and calligraphy.
  Different types of pens produce distinctive types of lines. Some, such as the crow-quill dip pen, produce slender and delicate lines. Other pens have a broader nib which can produce both thick and thin lines. Fountain pens and ballpoint pens are often regarded by many artists as being insensitive instruments or even not true "pen and ink" work, but are often useful for sketching in conditions in which a pot of ink would be a spill hazard. Many technical artists prefer the Rapidograph series of technical pens, which produce lines of extremely regular width.
  In art, pen and ink was originally used for quck sketches, often with a high degree of abstraction. George Romney produced a number of notable ink sketches of Emma Hamilton which are noted for the economy of his strokes, in which he produces instantly recognizable figures with a dozen lines.
  Later artists developed the pen and ink drawing into a finished artform, and many interior illustrations in books and magazines are done in pen and ink because they do not require halftone screening, unlike continuous tone techniques such as ink wash or painting.
  Pen and ink calligraphy was raised to a high level in Arabic, since Islam forbids the representation of living beings. In some forms of Arabic calligraphy, the letters were delicately formed to suggest an image related to the meaning of the phrase being written, without being an actual image of a living being.
  • silverpoint - method of drawing whereby a silver-tipped instrument is dragged across paper prepared with ground bone dust and gum water and then tinted with a pigment. The procedure results in drawings of extraordinary delicacy. It was used extensively in Europe from the late Middle Ages to the early 16th cent. The silverpoint instrument was a silver thread encased in wood, similar in design to a modern lead pencil. Among the foremost practitioners of the medium were Leonardo da Vinci and Albrecht Dürer. **

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Graphic design".

Bibliography
• Henry Petroski, The Pencil: A History of Design and Circumstance (1990); ISBN 0679734155

**The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved.