1, 2B is more accurate, and it is not easy to erase things that should not be wiped. 2B Erasers are very common in exams. Most lead cores on the market are 2B. Basically, the examination standards of large-scale examinations (senior high school entrance examination, national examination and college entrance examination) will be marked: "Please use a plastic eraser when changing multiple-choice questions". This is because the multiple-choice questions in these exams are generally changed by computer, and the judgment is based on distinguishing the carbon content on the surface of the paper. This is also the reason for specifying the use of 2B pencils.
2 and 4B are brown erasers commonly used by artists, made of soft and rough rubber. 4B Be soft when smearing, so as not to scratch the paper easily. Its design is convenient to erase large areas of traces without damaging the paper. 4B is mainly suitable for art students. But this eraser can't erase handwriting effectively and accurately.
Extended materials:
1, eraser principle
Pencil lead is made of graphite and clay. Graphite is soft, black and easy to stick to paper, so you can write. Rubber is very soft, with high friction and certain viscosity. If you wipe it on paper, you can stick the written words off without damaging the paper, so that you can erase the pencil words with an eraser. If you write with a ballpoint pen, the ink will penetrate into the paper and will not be easily erased.
2, the correct use of rubber
Pupils want to wipe the wrong words quickly and cleanly. They often dip the rubber in saliva and then wipe it. On the contrary, the typo is erased and the book is rotten. Especially for the students who draw, the backlit part of the sketch is often drawn, which makes them tired and dirty. At this time, if you keep rubbing or even vomiting, it will be broken!
The correct method should be: firstly, dry wipe a piece of white paper repeatedly to get a large number of "rubber surfaces", then gently pour the surface on the part to be erased, and then gently wipe it with a rubber. It will be clean after a while and won't damage the paper at all!
References:
Baidu encyclopedia-eraser