The Parallel pen is an ingenious invention. 2 pieces of steel plates placed parallel to each other to make up the nib so ink flows differently as compared to a regular fountain pen. Though the parallel pen is also a fountain pen, the ink flows along and across the entire the unique parallel plate structure that achieves a more beautiful and sharper handwriting than existing calligraphy pens. You can write and draw with the pen with any direction and orientation of the pen. To get sharper lines, you write or draw with the corners and vice versa. This is the most flexible pen I have ever seen.
Since I bought and used it a couple of months ago, I have not washed the pens yet. In my collection I have the 2.4mm, 3.8mm and 6mm. I used them without using the cartridge but by filling the barrel with ink. It will get messy if you are not careful with this. Cleaning is easy too. I do notice that the ink does not stain the inside walls of the pen barrel. I flushed the ink away with just water. I dismantled the nib from the feed with ease too, and then flushed them clean without a glitch. Putting the parts back is as easy as taking them apart. However I will be using the cartridge for the pens just so that I can preserve the lifespan of the pen as long as I wanted. Its hard to find parallel pens in Singapore ya know?
Just in case, here’s a sketch/ drawing I did with a 6mm Parallel pen.
You can achieve both thick and thin lines at the same time, depending on how you wield the pen.