What was the fundamental trade-off concerning ink quality before the ballpoint era?

Answer

Ink needed to be thin enough to flow but viscous enough to hold its shape until hitting the paper.

The persistent trade-off was that ink needed to be thin enough to flow rapidly through a fine point or capillary system, yet viscous enough to hold its shape until it met the paper surface.

What was the fundamental trade-off concerning ink quality before the ballpoint era?
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