How to see the quality of a writing brush? Or how to identify the quality of a brush hair?

You mean to identify it when you buy it! Because it doesn't make much sense to identify it after buying it. What I said above is basically to identify the handwriting at hand. It's just that it's really hard to identify when you buy it, and the boss won't let you take the exam! If you really want to buy a good pen, go to a bigger art painting and calligraphy shop. The price of good hair is definitely higher. According to my experience in buying brushes in small shops, basically those pens are not really good. You can buy it from him if the requirements are not high. When you buy them, you can only see if their hair is full. Other methods can only be bought. I hope I can help you!