Some recipes say to cover the pre-shaped dough during the bench rest, others say to leave it uncovered.
Could someone please tell me why?
To stop the dough from drying out but since a pre-shape isn't left to rest for so long many don't bother. I suppose there's no harm in leaving it uncovered if it's a short bench rest but if extended it would be better to cover.
I always try to cover to avoid getting a dried skin on the dough. To avoid using plastic too much, I cover it with the same bowl I used for mixing and bulk fermentation. If I have two loaves, the second one I just cover with a round banneton I am intending to use anyway.
When I do a preshape, which isn't often, I do cover it with a cloth to try to reduce a skin from forming.
Practice makes "perfect".
Preshape rest of 5 minute vs. 30 min. Higher vs. lower hydrated doughs. Breezy vs. still air Dusty vs. "clean" environment. Higher vs. lower ambient temperature.
Which will tend to dry the skin faster? Keep it clean and safe longer?
Place a tea towel over the dough. Good practice.