@trinsec It's only the tip part. The cartridge use some kind of grease to seal and should not be washed in this way. The first time I just throw the entire pen in it and then the cartridge leaks like a sieve 😂

The ultrasonic cleaner is really good at dealing dried carbon ink. For normal ink, wash the tip using tap water is good enough, but the carbon partical really stuck in the pen when completely dried.

This pen's vendor said the ink won't dry in 2 years, and I noticed the ink is completely dried, so... Maybe don't leave a pen untouched for so long?

@skyblond Heh. Sounds like a printer problem too. ;)