Carbon comes from nature. Carbon is very stable at room temperature and will not react chemically with oxygen in the air, so we have never seen carbon oxidized at room temperature, and the same carbon will not fade and disappear because of moisture in the air. Carbon has a strong stability, which proves that it will not react with acid and alkali, so the handwriting written with carbon pen is not easy to be changed. Even if it is changed, it is easy to see the traces of modification. Other carbonless pens are mostly synthetic raw materials, which will be diluted or react with other chemicals due to water quantity and oxidation, and eventually disappear or be modified. For example, we will find that words written in pure blue ink will be blurred after a long time. This is because the chemicals inside are oxidized by oxygen in the air, which will dissolve in water, make the handwriting blurred and be easily destroyed by various chemicals. There is a kind of pen called "magic pen" by many people. It can erase the words written in pure blue ink as clean as before. Charcoal can't, and it is clear and intact after a long time. The scriptures left by Dunhuang Grottoes were written by the ancients with a brush dipped in ink, which is a powerful proof that the handwriting is still intact after thousands of years.