I have always prewashed fabric...it does not matter how expensive it is or what I bought it for. My Grandmother and mother always did so I just automatically do it. I doesn't take that long but I feel better that when I am ready to use it the fabric is ready for what ever I decide to make out of it. I very seldom iron a piece, as I like to fold my fabric and if I have any skirt hangers or dress pant hangers use them for my washed fabric. But that's just me.