I recommend several very black inks. First, cheap carbon inks, most of which are very black, are typically Beijing carbon, which is more mobile than other carbon inks, and the price is less than 5 pieces of 5ml. Then there are noodier's ink's Eternal Black, Xfeather and black heart. These three types of ink are three-proofing inks (the ability to prevent modification even exceeds that of carbon). The purity of black is no less than that of carbon, and because it is not carbon, it is less likely to block pens. The disadvantages are that the price is more expensive (more than 1 9ml) and the smell is sour milk. Finally, we recommend Platinum Carbon and Syaraku Extremely Black, both of which are pigment inks, which should be considered as carbon, but carbon ions are extremely small, claiming to reach the nanometer level, which should not be as easy to block pens as ordinary carbon, and the price is similar to that of catfish.