I’m one hundred percent sure that we were all told that the blue side of the eraser is for rubbing ink. Our naive kiddish minds ended up trying that but failed miserably because the blue part is not meant for rubbing ink,you will be surprised.
Most of us have used erasers without questioning how it really works. According to Wikipedia, erasers were invented in 1770 by Edward Naime of England. Before then people used rolled white bread to erase.
From then erasers made of rubber began to be manufactured. The normal eraser is flexible and still a bit difficult to break. Here’s why this happens.
Erasers are primarily made of rubber from trees which is mixed with complex organic molecules like vinyl or fine pumice. It is then mixed with sulphur and heated to harden it ,a process called vulcanization.
Vegetable oil is also mixed with the vulcanized rubber to soften it a bit. Now,back to our main topic. The blue side of the eraser is meant to rub darker marks or rub pencil marks on heavier paper
The orange part should erase light marks on light paper. When rubbing the mark some heat is generated. The heat makes the rubber sticky enough to pull the pencil graphite pieces from the paper. This is why there are some small rubber pieces that are left on the paper after using an eraser on it.