In everyday life and work, each of us, to one degree or another, needs pencils. For people of such professions as an artist, engineer, technologist, designer and draftsman, such a value as pencil hardness is important.
History of the appearance of pencils
In the 13th century, the first prototypes of pencils made of silver or lead appeared. It was impossible to erase what they wrote or painted. In the XIV century, they began to use a rod made of clay black slate, which was called the "Italian pencil."
In the 16th century, in the English town of Cumberland, shepherds accidentally stumbled upon a deposit of material that looked very much like lead. They could not get a bullet and shells from it, but they managed to draw and mark sheep perfectly. Thin rods sharpened at the end began to be made from graphite, which were unsuitable for writing and very dirty.
Somewhat later, one of the artists noticed that drawing with graphite sticks fixed in a tree is much more convenient. So with simple slate pencils the case appeared. Of course, at that time no one had thought about the hardness of the pencil.
Modern pencils
The kind in which pencils are known to us today was invented at the end of the 18th century by the French scientist Nicola Jacques Conte. At the end of XIX and beginning of XX century. Several important changes were made to the pencil design.
So, Count Lothar von Faberkastl changed the shape of the pencil case from round to hex. This made it possible to reduce the rolling of pencils from various inclined surfaces used for writing.
And the American inventor Alonso Townsend Cross, thinking about reducing the amount of expendable material, made a pencil with a metal body and a graphite rod that can be extended to the desired length.
Why is hardness so important?
Any person who draws or drew something at least a couple of times will say that pencils can leave strokes and lines that differ in color saturation and thickness. Such characteristics are important for engineering specialties, because at first any drawing is made with hard pencils, for example T2, and at the final stage - softer, with the marking M-2M, to increase the clarity of the lines.
No less important is the hardness of the pencil for artists, both professionals and amateurs. To create sketches and sketches, pencils with soft stylus pencils are used, and for the final revision of the work, they are harder.
What are pencils like?
All pencils can be divided into two large groups: simple and colored.
A simple pencil has such a name because it is structurally very simple, and he writes with the most ordinary graphite lead, without any additives. All other types of pencils have a more complex structure and the mandatory introduction of a variety of dyes.
There are quite a few types of colored pencils , the most common are:
- ordinary color, which can be either one-sided or two-sided;
- Wax
- coal;
- watercolor;
- pastel.
Classification of simple graphite pencils
As already mentioned, graphite lead is installed in simple pencils. An indicator such as the hardness of the pencil lead is the basis for their classification.
Different countries have adopted various markings indicating the hardness of the pencils, of which European, Russian and American are most widely used.
Russian and European markings of black-graphite, as simple pencils are also called, differ from the American in the presence of both alphabetic and digital designations.
To indicate the hardness of a pencil in the Russian marking system, it is accepted that: T - hard, M - soft, TM - medium. To clarify the degree of softness or hardness, numerical values are introduced next to the alphabetic ones.
In European countries, the hardness of simple pencils is also indicated by letters taken from words characterizing hardness. So, for soft pencils, the letter “B” from the word blackness (blackness) is used, and for hard pencils, the letter “H” from English hardness (hardness) is used. In addition, there is also the marking F, coming from the English fine point (subtlety) and showing the average type of pencil. It is the European letter hardness marking system that is considered the world standard and is the most common.
And in the American system, which determines the hardness of pencils, the designation is carried out only in numbers. Where 1 is soft, 2 is medium, and 3 is hard.
In the event that no marking is indicated on the pencil, then by default it refers to the hard-soft (TM, HB) type.
What does hardness depend on?
Today, kaolin (white clay) and graphite are used to make lead pencil lead. The hardness of the pencil depends on the proportions of these substances mixed in the initial stages of production. The more white kaolin clay is laid, the harder the pencil. If the amount of graphite is increased, then the lead will be softer.
After mixing all the necessary components, the resulting mixture is fed into the extruder. It is in it that the rods of a given value are formed. Then the graphite rods are fired in a special furnace, the temperature in which reaches 10 000 0 C. After firing, the rods are immersed in a special oil solution that creates a surface protective film.