2, soot is also possible, soot plays an adsorption role here. But it can't be completely eliminated.
3, with rice grains, repeatedly press on the ink, and then wash it off; Then press it again, wash it again and repeat it many times. The purpose is to bond carbon as much as possible by relying on the adhesiveness of rice grains. Of course, it can't be completely eliminated. Minimize and dilute.
————————— If you think it's good, please adopt the answer and give a favorable comment. I wish you a better life.
————————————————————— I hope all your wishes come true, your work goes smoothly and your life is happy in the new year.