If you want to write calligraphy on a bottle, drill a small hole in the bottle first. If you want to write on the bottom of the bottle, drill another small hole in the bottom of the bottle. If you use a bottle cap to write on, drill a small hole in the bottle cap. When writing, press the hole on the bottle with your finger and loosen it from time to time. The ink will flow continuously towards the bottom or cap of the bottle. By controlling the air flow in the bottle, the flow of ink can be controlled.