stuart noble wrote in news:Qblgr.68233
:

Rockwool holds moisture but doesn't absorb it (if that makes any sense).
A J cloth works in a similar way, as do microfibre cloths etc.

Certainly rockwool holds water after it has become drenched. However, if
you were to half-submerged a wad of it in a pot of water, would the
unsubmerged part soon become wet too, say by capillary action, (in the way
some high-absorbent synthetic mops do)?

Al