tl;dr; you can't, cause the fibers are crinckled up in a lower energy state, but try soaking in 1 tablespoon of hair conditioner per liter of lukewarm water and

tl;dr; you can't, cause the fibers are crinckled up in a lower energy state, but try soaking in 1 tablespoon of hair conditioner per liter of lukewarm water and stretch.