Páginas: 8 (1984 palabras) Publicado: 9 de septiembre de 2010

1-según el video, cuántos lápices se fabrican en solo día en todo el mundo? :
a) 20.000.000
b) 16.438.356
c) 16.666.666
2-¿Cuál es la sustancia principal de la mina y de donde es extraída?:----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
3-Nombre por lo menos 7 procesos en la fabricación del lápiz:
1 ------------------------------------------------------------
4-Nombres los compuestos básicos para la elaboración de la mina de grafito:
5-cuál es la medida de las tablas ó troncos:--------------------------------------------------------------------

How are Pencils Made

Most of us use pencils almost every day in our lives. But have you ever wondered how are pencils made? Let us take a look at the manufacturing process of these writing devices, which were introduced for the first time in the 1600s
You may be surprised to know that the manufacturing process of thetraditional wooden pencils are still the same as that followed during the 1600s, when this writing device was introduced for the first time. The only difference is that now sophisticated machines are being used for this purpose instead of the traditional ones. The history of pencils can be traced back to the period of ancient Egyptians and Romans, who used a crude form of pencil called 'stylus', which werethin metal sticks made of lead. These sticks were used to make marks on 'papyrus', an early version of paper. The word pencil is derived from the Latin word pencillus, which means 'little tail'.

History of a Pencil

The history of a pencil takes us back to the early 15th century. The use of graphite in pencils started with the discovery of a graphite mine in England, during the 1500s.Soon, people started using it for marking sheep, as the graphite was so pure and solid, that it was very easy to cut it into sticks. Later, they realized that the graphite sticks required some sort of case to make it stable. They used strings or sheepskin to cover the sticks. Eventually, these cases were replaced by wooden ones, which are still being used worldwide. It was the Germans who, in 1662,introduced the method of using a mixture of graphite powder in pencils. Pencils have traveled a long way from the crude form used in the 1600s to the modern day mechanical ones. Contrary to conventional wooden pencils, these mechanical pencils lack the wooden case. The lead of this pencil is not attached to the case. Its mechanism makes it possible to extend the lead, as the tip of the pencil isworn away.
How are Pencils Made?
Even though the inner core of the pencils are made of graphite, people still call it lead. In reality, there is no trace of lead in pencils. The outer case of a conventional pencil is made of wood and the inner core consists of a mixture of graphite and clay. The inner core can also be made of colored pigments (to make color pencils) or charcoal too. Let us take acloser look at how are pencils made.
The primary task is to make the core of the pencil, which is known as 'lead'. Graphite, which is a soft mineral, is ground and is mixed with clay and water. This mixing process takes place in a mixing chamber, where the water is removed after the process. Then, the mixture is air dried to form a powder. This powder is again mixed with water to produce a...
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