My new 72 pack of gel pens are 75% unusable due to the ink in the gel pens being stuck at the wrong end of the pen and no ink near the tip? How can I get the ink flowing down the tube to the point? I've had them point down for 5 days now only 50% of the ink in the gel pens has actually traveled down to the tips...
You can easily utilize centrifugal force to move the ink to where you need it.
Grap the pen securely at the bottom end, letting the tip extend from your hand. Now quickly rotate your hand and move the tip of the pen in an arc around it. The centrifugal force will push the ink from the inner parts of the arc (the bottom of the pen) to the outermost part (the tip of the pen).
Start with only a few shakes. Depending on how liquid the ink is, you may shake some ink out of the tip, creating a real mess inside the pens cap.
A similar technique is used to "shake down" old-fashioned thermometers.
Heating the ink cartridges will do it easily. Remove the cartridge and hold it under a stream of hot water. If it has dried in the nib, hold just the metallic tip in the flame of a lighter for 1 to 3 seconds. Either singlely or combined these techniques should restore an old ink pen to functionality. The nib-in-flame method can be used to squeeze out a little more from a dead pen.