It's one of life's little frustrations. Your pen has ink but won't write. Don't throw away the pen just yet. There are a few things to try if you have an ink pen that is not working.
It helps to understand what kind of ink is in your pen and what delivery mechanism is used to get the ink from pen to paper. Although exact formulas differ from brand to brand, all inks contain pigments or dyes, solvents and other chemicals that are added to improve the quality of the ink and extend its useful life.
When troubleshooting computers, Help Desk personnel first ask, "Is the computer plugged in?" It seems obvious, but users sometimes forget that their problem may have the simplest of solutions. Before trying anything else, make sure the pen has ink. You may only need to install a refill to get your pen working again.
Some papers accept ink better than others. If a paper, or even a section of paper, has a slightly waxy or oily surface, a ballpoint pen slides across it, rather than roll, and the mechanism for getting the ink flowing is not activated. The wax or oil acts as a barrier to the absorption of wet inks such as those used in gel pens and fountain pens.
Ballpoint pens use oil-based ink. The advantage of oil-based ink is that it dries faster than other inks. It's a thick ink, more like a paste than a liquid, so you use less of it. The downside is that thick, fast-drying ink is more prone to clumping.
If the pen has ink but won't write, try scribbling on a piece of scrap paper to get the ink flowing again. If that doesn't work, expose the pen tip to the heat of a blow dryer for 8 to 10 seconds. You can also try heating water to just under the boiling point and letting the pen sit in the water for 10 or 15 minutes to warm the ink. Using an open flame, such as from a match or lighter, is not recommended because it could melt the plastic pen body.
Rollerball pens are designed in the same way as ballpoints, but they use water-based ink. Water-based ink flows quickly and soaks into the paper more easily than oil-based ink. The trade-off for smooth delivery is that you use more ink. Rollerballs run out of ink faster than ballpoints.
Gel pens combine the advantages of the ballpoint and the rollerball. The consistency of the ink is somewhere between the two. It is water-based and comes in a wide variety of colors. Like a ballpoint, temperature change is the most likely culprit for dried ink. Apply heat from a blow dryer or immerse the pen in hot water for 10 to 15 minutes.
If you find a fountain pen ink is not flowing, the problem is likely dried ink or a clogged nib. New pens can become clogged with sediments in the ink, while used pens dry out over time. Nibs collect particles of ink, dust and paper fiber. Remove the ink cartridge and run warm water through the pen to dislodge small particles and dried ink.
If plain water doesn't work, you may want to use a pen flush product, formulated especially to dissolve inks and ink sediments. You can purchase pen cleaning solutions anywhere fountain pens and inks are sold. You can also make your own solution with a small amount of dishwashing soap, a 10 to 1 solution of ammonia, or a 20 to 1 solution of household bleach.
Do not use ammonia to clean aluminum, brass or copper pen components because even a mild solution corrodes the metals. Do not combine ammonia and bleach, as together they create toxic fumes.