Has anyone tried a silk pillow case or wrap? And if so what brand? I'd been pondering for ages as the hair wraps aren't cheap. I recently bought one around the £50 mark. BUT it kept slipping back in the night so I'm not impressed. Saying that, my hair definitely looked less frizzy! I'm interested in opinions on the pillow cases also, to see if they do improve the appearance of pillow face!! Thank you