Little Rubber University asked

  Even today with advanced technology, pencils and erasers still do not forget their mission. In the process of using pencils, we will inevitably make mistakes. What should we do at this time? Of course it was erased with an eraser! But have you ever wondered why an eraser can erase pencil marks? And some of the erasers work well, some of them make the paper black even if they wear out!
  Before discussing how the eraser works, let’s first understand what you are erasing. Most pencil refills are made of a mixture of materials such as graphite and clay. When you write with a pencil, the graphite particles in the pencil will fall off and adhere to the surface of the paper due to friction, leaving marks on the paper. When erasing these marks with an eraser, because the eraser is more absorbent, part of the graphite particles will run away and adhere to the eraser, while the other part will be swept away with the paper fibers due to the friction of the eraser. Therefore, the pencil marks can be erased, and the paper becomes thinner and thinner.
  Then why are some erasers so useful, but some are unhelpful? Don’t rush to deny its quality, this may be because you did not choose the right eraser. The composition of the eraser is mainly natural rubber, synthetic rubber or polyvinyl chloride. In addition, vegetable oil, sulfur, pumice powder, etc. are added to adjust its softness and hardness. The composition of the eraser will be adjusted according to the different uses of the eraser. For example, if the proportion of softeners such as vegetable oil increases, the eraser will become softer. On the contrary, if the proportion of sulfur is increased, the rubber will become harder; if the proportion of pumice powder is increased at the same time, the rubber will become harder and coarser and more abrasive.
  The meaning of the eraser is attached to the pencil, and its grading is adapted to different pencils. The pencil lead can be divided into different grades according to the graphite content. Generally, “B” means soft pencil, “HB” means pencil with moderate hardness, “F” means pencil with hardness between HB and H, and “H” means hard pencil. From B to H, the lower the graphite content, the harder the pencil, but the lighter the color. Therefore, it is also very important to choose different pencils according to different uses and different erasers according to different pencils.
  It seems that a small eraser also has great knowledge!