The main components of the lead core of the pencil are graphite and clay. According to the national standard, pencils are divided into 18 models according to the graphite concentration. In the current standardized test in our country, the computer can only read the pencil handwriting with a lead concentration of 2B. Too thick or too light will cause the computer to fail or error in reading.
Early pencils contained lead, but the main components of the pencil refills people now use are graphite and binder, which no longer contain lead and are harmless to the human body.