Any way of safely cleaning and flattening LEGO Sails ?

THANKS !

I have ironed a set of Black Pearl sails before. I used a little spray starch too when I was doing that to give them a little bit of stiffness. They were close to how they came from Lego but not quite as rigid. Display wise they looked fine. Everything you do will possibly fray the edges a little so don’t get too rough on them. 

Warm, soapy water (I use dial) has always worked well for me. Either a clean sponge or soft brush with light pressure to remove any stains or discolor. Don’t be afraid to soak them depending on their level of filth. When drying I like to keep something flat and heavy pressed on them. (A book, box, pan, etc essentially anything clean flat & heavy as I mentioned before). And I usually use a clean counter top as the base surface.  This helps retain or correct the original shape.  Good luck 👍