Shower cap? Wet dreads??

I thought getting your hair wet in the dreading process was a normal way to dread? You get them wet, then as they dry they tighten up and it helps the dreading process?

 

I tend to wash my dreads every few days in the shower, but when I do i dont really soak them - just get them wet enough to use some residue free soap etc, and after washing they seem to tighten up a little