Regardless of the brand, every pen requires a little care.
We're often asked how to care for your fountain pen, especially if you're buying your first one and are concerned about its "health." That's why we've decided to create the following guide, which we hope will help you clear up any doubts.
What is a fountain pen made of?
First, a few words about the construction of a fountain pen. First and foremost, it consists of a barrel and a cap. Removing the cap reveals the nib, which is placed on a slide. The slide is a partially smooth, partially ribbed plastic element visible beneath the nib.
The part we grip while writing is the section. The section conceals the body, which houses the filling system, i.e., the cartridge or converter/piston. In some pens, such as the MD Paper, the section is transparent, allowing us to observe the ink flowing into the feeder.
When you examine a nib, you'll notice a slit running through its center, called a channel, dividing the nib tip into two parts—wings. At the top of the channel is an air vent—sometimes heart-shaped. The tip of the nib, the part that touches the paper while writing, is called the grit or iridium. The grit size determines the line thickness of our pen.

The transparent section allows you to watch the ink flow into the feeder.
First use
When you've bought your dream pen and filled it with ink, and it suddenly refuses to work, stopping altogether, or simply won't write, don't be discouraged! During the manufacturing process, pen parts can become greasy, and although manufacturers clean them before delivering them to you, it's possible that some parts haven't been degreased effectively enough. In such cases, plain water and a drop of dish soap poured into a container to rinse the pen are sufficient. Wipe the nib and feed tube with a soft brush (e.g., a toothbrush). Then rinse them under running water, and... the problem usually disappears.
Similarly, if the nib doesn't want to write right away, give it a chance. Sometimes the process of ink flowing into the feeder takes a little longer. Don't write it dry! Scratching the paper with a dry nib or pressing it against the surface is damaging the pen. The nib can bend, and micro-frays of paper will get caught between its wings, effectively clogging the ink channel.

The MD Paper fountain pen has a transparent section.
How to take care of your pen so that it lasts as long as possible?
Above all, always use inks from proven, popular brands in your pens. If you're unsure whether an ink is suitable for your pen, read about it, seek out information, and ask the seller for recommendations.
Try not to use iron gallium inks, let alone inks, in fountain pens. We also need to be careful with pigmented inks. The microparticles that make the ink deep and fade-resistant can clog the pen, especially after prolonged periods of inactivity. Always read and follow the manufacturer's recommendations.
Sometimes, however, we've used good-quality ink or ink cartridges, but our pen still won't write. It stops, dries out, or splatters. Don't be discouraged—not all pens work well with all inks! Before writing off the ink (or worse, the pen!), try it in a different pen. Sometimes that's enough!

Feather likes baths…
Every time you change ink, you should rinse the pen. To do this, remove the cartridge or plunger, place the unscrewed barrel with the nib down under a stream of lukewarm running water, and rinse until the water comes out clean. Alternatively, when filling the pen with the plunger, you can draw in water and push it out until it runs clear.
We rinse the fountain pen even if we're changing ink colors from the same brand. This isn't just to avoid mixing colors, but also to prevent any potential reactions that could cause sediment to form in the inks, clogging the fountain pen. Historically, this has even happened within a single ink family with two different colors.
If we plan to not write with the pen for more than two weeks, we also remove the ink. When we want to use it again, we'll be sure it will start up without a problem.
Remember, though, that while we use various soaps, gels, balms, oils, and other products for daily hygiene, we should only bathe the pen in water with a drop of dish soap if necessary! For safety's sake, we don't use any preparations to clean the pen, especially not alcohol, vinegar, or other harsh cleaning agents. Distilled water is also not necessary. 
For Trouble – Pen Doctor
If we truly want to take good care of our beloved fountain pen, we can give it a periodic inspection and service. Doing so every few months will protect us from unexpected surprises while writing. A group of so-called Pen Doctors in Poland handles servicing, and indeed, the service. At Escribo, we recommend Przemysław Dudek and his Pen Repair Shop.
Pen Doctor will also repair your pen if it begins to malfunction. We sincerely advise against attempting any repairs yourself, as untrained hands can do more harm than good. It's especially common to hear that a scratchy pen can be sanded down with sandpaper. Unfortunately, this can damage the nib's grain. Sudden scratching can be caused by uneven pressure on the nib while writing. If you tend to rotate the pen while writing, try not to. A slight difference in wear on either side of the grain is enough to cause the pen to have "one leg shorter" and your writing will begin to limp.

We hope our guide has cleared up any doubts you might have and answered some of your questions. We also encourage you to ask your questions in the comments below.