The main component of pencil lead is graphite. In fact, the pencil refill is made of graphite and clay in a certain proportion, but the paint on the outside of the pencil contains lead, so students who like pencils should remember not to contain pencils. This habit must be changed. Contains the disadvantages of pencils:

1. Ordinary pencils with excessive blood lead are coated with multiple layers of paint or a layer of colored plastic film. Paint and colored plastic films contain high lead content. Children biting pencils for a long time will lead to excessive blood lead, which will lead to children's inattention, irritability and short stature, which will seriously infringe on children's neurological function and make children suffer from TIC disorder and other diseases.

2. Children who are prone to various oral cancers often bite pencils or even put sharpened pencils in their mouths, which will puncture the oral mucosa, forming a vicious circle of ulcer-repair-healing-puncture-re-ulcer, and suffering from self-injury ulcers. Long-term recurrent self-injury ulcer is the main cause of oral cancer such as tongue cancer, lip cancer and jaw cancer in children.

The development stage of pencil:

1, the first stage, the birth of graphite: at this time, the "graphite pencil stick" is still in the original stage of writing; 1564, a black mineral-graphite was discovered in a place called barodale, England. Soon, some local shepherds found that they could mark their sheep with graphite. Inspired by this, people cut graphite blocks into small strips for writing and painting. But graphite strips are easy to get dirty and break.

2. In the second stage, the early pencil: the birth of the wooden pen container: after a hundred years of development, the "pencil" at this time entered the primary stage of its own evolution, and a wooden pencil shaft appeared, becoming a semi-finished product of the "pencil". This pencil rod is mainly used in the market, and users need to sharpen it again before using it.

3. In the third stage, the birth of the pencil with a cap: With the widespread use of pencils, a series of problems of the traditional pencil rod were exposed, which brought people a lot of troubles, such as unsanitary use, easy breaking of the nib, and difficult carrying, which brought new challenges to the progress and development of the pencil industry, and the appearance of the pencil with a cap solved the development bottleneck of the modern pencil industry in product innovation.