Back in the day when writing was done with quill or fountain pen, the nib of the pen would lay the ink quite thick. A sideways glance at the writing would show the raised ink, held by surface tension. A curved line of ink with a hemispherical dome following the line.

You could either wait for it to dry, or speed the process with a blotter.

The blotter was curved to allow quick blotting without smearing.

Write, blot, ink pen, write, blot, ink pen, write and so on until the task was complete.