What quality of thread did the Water Frame produce that allowed for a shift in fabric composition?

Answer

A thread significantly harder and stronger than the Jenny's, suitable for warp yarn.

The Water Frame produced strong warp yarn, which meant that for the first time, Britain could produce entirely cotton cloth without needing to rely on linen or wool for the foundation warp threads.

What quality of thread did the Water Frame produce that allowed for a shift in fabric composition?
inventiontextile