First, the basics!
Almost all fountain pens are comprised of the same basic components: a nib (also called a point, this is the decorative metal writing tip of the fountain pen, available in stainless steel, rhodium gold and other metals), a feed (the ribbed component attached to the back of the nib), and the ink supply (various options here include: cartridge, piston, converter, plunger, vacuum, and sac). Many people do not realize that there are certain care requirements for Fountain Pens and that if they are followed many "problems" can be resolved or never start.
A fountain pen should be cleaned after every second filling of either ink from a bottle or cartridge. Which means, if you use the pen and you replace the cartridge, insert another and then run out, clean the fountain pen before you install the third cartridge or fill from an ink bottle.
Cold Rinse Only!
Fountain pens should only be cleaned with clean, cool water. IMPORTANT: NEVER USE HOT WATER. Hot water can easily damage the feed. If your fountain pen is excessively dirty, a teaspoon of ammonia can be added to a cup of water, then soak the nib section overnight. You can also use a window cleaner like "Windex", just be sure it has ammonia as this helps break up dry ink and dirt the best.
Flushing the Nib
Flush the nib section with water until it runs clear. You may use the faucet's power or you may use a ear syringe and force the water thru, this is very effective since it gives more force and cleans the nib out better.
Drying After Washing
Cover the nib section with a soft dry cloth and shake it a few times to force the water out. It is best to do this right before bedtime and leave it to dry overnight. In the morning just pop in a cartridge and you are ready to write! We use a store bought toothbrush rack with a soft paper towel folded where the nib will rest. You can put the freshly cleaned pen in one of the slots and let the capillary action from the towel draw the wetness out. This is very effective and we clean our pens like this in the store. If your pens are piston fed only (only bottled ink can be used) you can soak your pens first in water then suck fresh water into the chamber and evacuate the water. Do this 3x or until the water runs clear. Some pens like Aurora and Pelikan have nibs that easily unscrew which makes cleaning the chamber with a "q-tip" easy if you wish.
Storing Your Fountain Pen
Never store your fountain pen lying down. The ink will coagulate and dry in the nib section and make it difficult for the ink to flow and for the pen to write properly. Keep your pen capped with the nib pointed up in a pencil cup or other type of holder. Toothbrush holders work great at our stores. Find one that suits your pens size(s). If you are not going to use your pen for a week or more, evacuate the ink or remove the cartridge. Pen cases where the pens lie flat are great ways to store UNFILLED pens.
Travel With a Fountain Pen
Although some pens are said to be "leak proof" on planes, its always best to be safe and evacuate your pens before you get on any plane. Cartridge pens are great for travel since this is so easy to do. When you get to your destination just pop one in. Air pressure in a plane can decrease and increase during a plane's ascent, flight and descent, and this can cause any pen to allow ink to "drip" into the cap. It's really not leaking, but it is messy.why bother?
Cleaning: Sterling Silver
Fountain pens come in many finishes and are constructed of a wide variety materials, so their care varies from material to material. Silver, sterling and plated: use a store bought polishing cloth or glove infused with silver cleaner. For hard to clean patterns and finishes such as "barley etched", use a liquid silver polish with a soft brush to get the polish and tarnish out of the crevices.. Remember silver is a soft metal and will take on a patina and will show scratches and even small dents, it's part of it's "charm" but this material requires extra TLC.
Cleaning: Hard Metals
Platinum, palladium, rhodium, stainless steel and chrome: These finishes generally do not tarnish and remain "mirror like". While they can show scratches and wear, they are much more durable than Sterling and/or silverplate. A soft cloth will remove fingerprints and dirt.
You may think that lacquers are delicate but in reality they are quite durable, especially "Chinese Lacquer" that S.T. Dupont uses on their pens. You should only use soft cloths to clean these pens, never any abrasive cleaners or chemical compounds. They will give you many years of pleasure. As with any painted or lacquered item, surface chips may occur if the pen strikes a hard/sharp surface.
This predecessor to our modern plastics seems to be quite at home in Italy, which produces most of the world's celluloid pens. Celluloid is very durable since the bars used to make the pens are a solid resin. It is still possible to chip and crack them if they are abused. A soft cloth is all that is needed to clean them.
Cleaning: Fine Resins
This material gives many pens like Mont Blanc's precious resin pens their light weight, which some people prefer. However this also makes them quite vulnerable to cracks and breakage if dropped or abused. They will also show slight scratches in the barrel over time, especially with dark colors. Care must be taken. A soft cloth can be used to clean and polish resin pens. A good rule of thumb is to invest in a leather pen case to help protect them.