Unscrew and remove the Rotring technical pen's cap. Unscrew and remove the barrel from the pen body and nib assembly. Unscrew and remove the color-coded ink cartridge clamp ring from the pen body. Pull off the ink cartridge and rinse with clean water. Scrub the cartridge interior with a pipe cleaner if necessary.
Tap the back of the pen body on a paper towel to remove residual ink. Unscrew the nib from the pen body using the nib key. Flush the nib and pen body under a faucet of lukewarm water, or soak the parts in a cup of Rotring technical pen cleaning solution. The nib and pen body may also be flushed in a cup of cleaning solution using a large rubber bulb.
Shake off any remaining fluid and wipe all the parts dry with a paper towel. If desired, fill the ink cartridge with technical pen ink. Reassemble the pen and store it with the cap on and the tip facing up.