pencil

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pencil,

pointed implement used in writing or drawing to apply graphite or a similar colored solid to any surface, especially paper. From prehistoric times lumps of colored earth or chalk were used as markers. The Egyptians ruled lines with metallic lead, as did medieval monks. The so-called lead pencil—a rod of graphite encased in wood—came into use in the 16th cent. From the late 18th cent. pulverized graphite was mixed with clay to bind it and to provide different degrees of hardness—the more clay, the harder the pencil. Today the mixture is forced through dies, cut to the required length, and kiln-fired. The rods are laid in grooves of a thin board, a similar board is placed over them, and the wood is shaped into pencils, usually of round or hexagonal cross section. Pencils are also manufactured with cores of colored pigments mixed with clay and wax and of other materials. Mechanical pencils are commonly made of metal or plastic, the cores (or leads) being advanced by operating a screw mechanism or a propel-repel ejector mechanism.

Pencil

 

a rod made of coal, lead, graphite, or dry pigment that is used for writing, drawing, or sketching. It is often encased in a wood or metal holder. Prototypes of the pencil included metal points, lead and silver pins that were inserted into metal holders. Used from the 12th to the 16th century, metal points produced a dark gray tone. The black chalk pencil, which was made of black clayish shale and produced a soft dull shade of black, was introduced in the 14th century. Beginning in the 16th century, graphite pencils and pencils made of charred powdered bone bound with gum were widespread. Graphite pencils provide dull strokes with a slight luster. Charred powdered bone produces mat black marks.

In 1790 the French scientist N. Conte invented the wooden pencil. At about the same time, the Czech scientist J. Hardtmuth proposed the manufacture of writing instruments made of a mixture of pulverized graphite and clay. In principle, this method forms the basis of the modern process of pencil manufacture. Mechanical, or automatic, pencils appeared in the second half of the 19th century and became particularly popular in the 20th century.

Depending on various manufacturing techniques and writing properties, there are different kinds of pencils, including black lead (graphite) pencils, colored pencils, and copying pencils. Pencils are also classified according to their use; for example, there are school, office, drafting, drawing, lettering, carpentry, and cosmetic pencils. There are also pencils used for retouching, marking, and labeling various materials. Special types of pencils include pastels and sanguine (red chalk).

In the USSR lead drawing pencils are made in several degrees of hardness, which are indicated by the letters M (soft), T (hard), and MT (medium hard). Numbers often precede the letters; the higher the number, the greater the degree of hardness or softness. Outside of the USSR the letters B and H are used instead of M and T, respectively.

The writing cores of pencils consist of a tightly pressed, uniform mixture of minute particles of different materials. Lead cores contain graphite, colloidal refractory clay (bentonite), a binder (tragacanth or pectin cement), and fats or wax. Colored leads are made of pigments, kaolin, bentonite, talc, a binder, and fats. Copying, or tracing, leads are made of water-soluble pigments (primarily methylene quinone), graphite, talc, bentonite, and a binder.

There are various types of mechanical pencils. In the split collet type, the lead is propelled by the turning of one of the pencil’s components. The propel-repel-expel type has a button that forces the lead through a bored tip. Multicolored pencils have two, four, or more cores that can be alternately pushed through the holder.


Pencil

 

a certain type of family of curves in a plane or a certain type of family of surfaces in space. In analytic geometry, a pencil of lines is the set of all straight lines in the plane that either are parallel (a pencil of parallel lines) or pass through a point O in the plane (a pencil of lines through a point). The point O is called the vertex of the pencil. If the equations of two straight lines of the pencil

A1x + B1y + C1 = 0 A2x + B2y + C2 = 0

are given, the equation of the pencil can be represented in the form

λ(A1x + B1y + C1) + μ(A2x + B2y + C2) = 0

where the parameters λ and μ take on any values but do not simultaneously vanish.

A pencil of planes is the set of all planes that either are parallel or pass through some line, which is called the axis of the pencil.

pencil

[′pen·səl]
(engineering)
An implement for writing or making marks with a solid substance; the three basic kinds are graphite, carbon, and colored.
(mathematics)
In general, a family of geometric objects which share a common property.
All the lines that lie in a particular plane and pass through a particular point.
All the lines parallel to a particular line.
All the circles that pass through two fixed points and lie in a particular plane.
All the planes that include a particular line.
All the spheres that include a particular circle.
(optics)
A bundle of rays that emanate from or converge to a common point.

pencil

1. a narrow set of lines or rays, such as light rays, diverging from or converging to a point
2. Archaic an artist's fine paintbrush
3. Rare an artist's individual style or technique in drawing

PENCIL

Pictorial ENCodIng Language. On-line system to display line structures. Sammet 1969, 675.
References in periodicals archive ?
NP-modified electrodes can be obtained by electrodeposition [140, 161, 203] or by simply immersion of the pencil lead into the NP solution [25, 32, 188].
5 images of the stress distribution around the pencil lead are shown at distinct time steps before and after fracture.
* Pencil lead isn't really lead--it's made of graphite and clay.
With a pencil lead sheet, you can learn within five minutes whether the client is a fit or whether you need to tell the prospect you're booked solid.
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The company says the problem stems from the fact that the pencil leads have to be soft in order to produce bright colors, but that children often press down hard when they color.
The "lab-on-a-chip" consists of a tough, glass-like container with 16 to 36 tiny printed dye spots, each the diameter of a pencil lead. The chemicals in each spot react with sweet substances in a way that produces a color change.
Different stacks don't stick together well, which is why pencil lead is soft.
In Absentia (Brothers Quay) In the twin animators' live-action, close-up study of a mad woman furiously scribbling letters to her dead husband, the forlornness of pencil lead is inscribed on our brains to the excruciating drones of Stockhausen.
ANSWERS: 1 Cambridge, Massachusetts; 2 Bangladesh; 3 The Bank of England; 4 A transformer; 5 The sea otter; 6 Kramer vs Kramer; 7 Pencil lead; 8 Northampton; 9 Hudson the butler; 10 V[sz]clav Havel.
Figure 6(b) shows an example of combined response function of specimen and AE measurement system determined using pencil lead breaking.