in daily life and work, each of us, in varying degrees, need pencils.For those professions such as artist, engineer, technologist, designer and draftsman important value such as hardness pencil.
story of pencils
In the XIII century the first prototype of pencils are made of silver or lead.Clear that they were written or drawn, it was impossible.In the XIV century, began to use a rod made of clay of black shale that is called "Italian pencil."
In the XVI century in the English town of Cumberland shepherds accidentally came across a deposit of material that looks very similar to the lead.Bullets and shells out of it was not available, but the draw and labeled sheep they turned out great.From graphite to produce thin steel rods, sharpened at the end, which is not suited for writing and very soiled.
Later some of the artists noticed that draw graphite sticks laid down in a tree, much more convenient.That's how simple slate pencils and body appeared.Of course, at that time about the hardness of the pencil, and no one has yet thought about.
Modern pencils
The kind in which pencils are known to us today, invented in the late XVIII century French scientist Nicolas Jacques Conte.At the end of the XIX and early XX century.the design of pencils have been several important changes.
So, Count Lothar von Faberkastl changed the shape of the body of a pencil with a round on the hex.This reduced skatyvaemost pencils with different inclined surfaces used for writing.
A US inventor Alonzo Townsend Cross, think about reducing the amount of consumable material in pencil with a metal housing and push to the desired length of the graphite rod.
Why is it so important hardness?
Anyone, even a couple of times that a draw or hell, say that pens can leave the strokes and lines that differ in the saturation of color and thickness.These characteristics are important for engineering graduates, after any drawing executed first solid stick, for example T2, and at the final stage - a soft, labeled M-2M to increase the clarity of the lines.
Equally important is the pencil hardness and artists both professionals and amateurs.To create sketches and drafts Use a pencil with soft leads encased, and for the final completion work - harder.
What are pencils?
All pens can be divided into two groups: simple and colorful.
pencil has the name because it is structurally very simple, and he writes the most ordinary graphite pencil, without any additives.All other pencils are more complex and required the introduction of the various dyes.
Species colored pencils pretty much the most common - is:
- usual color, which can be either unilateral or bilateral;
- wax;
- coal;
- watercolor;
- pastel.
Classification of simple graphite pencil
As already mentioned, in pencil graphite pencil set.This figure, the hardness of the lead pencil is the basis for classification.
Different countries have different markings indicating the hardness of pencils, of which the most widely used European, Russian and American.
Russian and European labeling chernografitnyh is also known as pencils, different from the American presence as a literal as well as digital signage.
to designate the hardness of the pencil in the Russian system of marking assumed that: T - firm, M - soft, TM - medium.To clarify the degree of softness or hardness introduced near the alphabetic, numeric values.
European countries pencil hardness as denoted by the letters, taken from the words characterizing the hardness.So, for soft pencils used the letter «B» from the word blackness (black), and for solid - the letter «H» from the English hardness (hardness).In addition, there is also marking F, going from English fine point (fineness) and shows the average type of pencil.It is the European system of labeling hardness letters is considered the global standard and is the most common.
In the American system, which is determined by the hardness of pencils, marking is carried out by only numbers.Where 1 - mild, 2 - medium and 3 - hard.
In that case, if not specified, no pencil marks, then by default it relates to hard-soft (TM HB) type.
What determines the hardness?
today for the manufacture of graphite pencil lead pencil used kaolin (white clay) and graphite.From the proportions of the substances mixed in the initial stages of production, it depends pencil hardness.The more laid white kaolin clay, the harder the pencil is obtained.If the increased amount of graphite, the pencil is softer.
After mixing all the necessary ingredients obtained mixture is fed into the extruder.This is where the rods forming the set value.Then fired in a graphite rods special oven in which the temperature reaches 10 0000S.After firing, the rods are immersed in a special oil solution, creating a surface protective film.
