HB pencils are mainly used for writing. Its handwriting is darker than H pencil, but easier to erase than B pencil. The more B, the darker and softer the pencil, and the more H, the lighter and harder it is. It is difficult to see clearly if the color is too light, and it is difficult to modify and erase if the color is too dark. HB is just right.

According to the hardness of the refill, it includes 10B~2B, b, HB, f, h, 2H~ 10H. The refills of most pencils are graphite, but graphite is too soft, and clay needs to be added to enhance the firmness of the lead core. The classification of pencils is based on the different proportions of graphite and clay in the refill. Generally divided into three categories: h, HB and B.

Source of pencil:

1662, the world's first pencil factory was built in Nuremberg, Germany: Shidelou Pencil Factory. Later, F. Kaster, a German, founded Faber Kaster Graphite Pencil Factory in Nuremberg. The lead core was made by heating with sulfur, antimony and other binders and mixing with graphite, which made the manufacturing technology of graphite pencil rod take a big step forward.

N·J· Kant of France used the method of washing graphite for the first time to improve the purity of graphite, and bonded graphite with clay to make a refill. This method is called Kong Defa. It laid the foundation of pencil industry.

Later, after repeated experiments, Comte, a French chemist, changed to clay as a reinforcing agent, and the prepared refill was more solid and wear-resistant. Moreover, this method was suitable for any graphite mine and has been used for 20 19 years.

William Monroe, an American carpenter, embedded a black lead into a wooden strip with a groove, and then spliced the two wooden strips together to make the world's first pencil rod.