What critical engineering shift did the ballpoint pen represent compared to previous writing tools?

Answer

The focus moved from managing fluid dynamics to managing surface contact and viscosity.

The success of the ballpoint masked a crucial engineering shift where the focus moved entirely from managing fluid dynamics (how thin ink flows) to managing surface contact and viscosity (how thick ink rolls).

What critical engineering shift did the ballpoint pen represent compared to previous writing tools?
inventionHistorywritinginkpen