Jinhao ink cartridges have a neutral PH, excellent coverage, smooth flow. <br><br> <b>How to fill a fountain pen with cartridges</b>: <br><br> Insert the narrow end of the new cartridge into the black of section block with enough pressure to create a snug fit. The pin inside the section block will puncture the seal of the cartridges, allowing ink to flow into the section block. Screw the barrel on over the cartridge into the section block. <br> When you fill the pen at the first time, you can swing the pen to make a few drops of ink coming out of the nib, so that it can flow easily.