The cartridge / converter ink systems are very common in contemporary fountain pens and the TWSBI Micarta features this system. This ink filling system has many benefits with the only downside being that the ink capacity is less than those that feature an integral ink reservoir (and maybe it isn't as fun to watch fill with ink as say a vacuum filler). This type of pen design opens up the option to using ink cartridges which is handy when you need a refill on the go or travelling. This ink converter is a piston type. To fill the pen you need to turn the knob element at the end of the unit to drive a piston either up or down inside the ink reservoir. This action will either draw ink into the pen or discharge it. Ink converters / cartridges are friction fit onto the nib section and come in a few differing sizes, the TWSBI Micarta is an International size unit which is common for a variety of pen brands. Some companies have proprietary sized converters/cartridges like Waterman, Parker, Sheaffer, and Lamy to name a few.
     One important discovery that I have made is that not all converters work like you would expect, on two (2) separate pens I have experienced flow issues were the ink was drying faster than expected and pen had trouble starting when put to paper. At first I thought it was the ink, then the nib, but the issues were resolved by swapping the converter. An easy way to tell if the converter is the problem is to use an ink cartridge with the pen that is giving you trouble and if experience no issues when using the cartridge, a simple replacing of the converter is all that the pen needs.
     The design of cartridge/converter pens separates the ink delivery system from the ink storage system making it easy to maintain, clean, and service. A great design for those that prefer to use many different inks as it takes very little effort to flush the pen clean of any ink and if the ink happens to stain the converter, replacing the converter is not too costly.

   With the Penatomy series of posts the idea is to dissect common filling systems to show the component parts that make up our favourite writing instruments.