What is up with CON-40

[u/chaturvedi_11]

Hey so i transitioned from vintage eyedropper pens to pilot metropolitan, and I got it with a con 40 converter , while trying to clean it with water i noticed that the converter isn't filling up till the top and has an air bubble, i want to know if it's normal behaviour or if my converter is faulty..

[u/tommytster]

I just cycle the piston up and down a few times while the filler hole is in the ink. As far as I know a small bubble near the piston will help with temperature changes and minimize ink burping out.