eli5 Why is it hard to rewrite over a spot where a ballpoint pen failed, but scribbling elsewhere works?

Question

I wish I could just attach a picture, but here’s the sequence:

1. Writing and the pen stops working
2. Scribbling and drawing circles to see if the pen still works. It does.
3. Go back to writing in the spot the pen stopped working. It won’t work!!! ?!
4. Repeat 2 and 3

In: Technology

Answer 1

There’s often a drop of oil after the ink in the cartridge to prevent it from exposure to air and drying out.

When the ink runs out, you start writing with this oil instead. Writing on oily paper is hard.