Kevin got in touch ask why clothes dried on a washing line can end up feeling rough, crunchy and stiff... To find out, our Laura Brooks contacted Neil Lant at the Fabric and Home Care research and development division of Proctor and Gamble, who make Lenor fabric softener.
Did you use fabric-softener sheets in your dryer? Even if you did not, the agitation of the dryer would likely loosen up the fibers some, making them more pliable. Atomic-S, Sat, 20th Aug 2016
I agree with Atomic; the movement within the mechanical dryer would have loosened up the materials by the time you came to collect the dry results. Except when it is very windy, most clothing remains relatively static on the washing line and hence is not subject to the same perturbation.
Moisture on a fabric will tend to pull fibres together. It may be that not all water molecules are lost during slow evaporation. This will tend to 'glue' fibres together. On a windy day the moisture that would have remained would then be ejected by the airflow. In a drier the hot air may have an ionising effect. Not sure on that one. jeffreyH, Sat, 20th Aug 2016