I'm concerned with the term "ripples". Are you speaking about ripples when you fold the fabric and match the selvages there are ripples on the fold? If so, it's because you fabric is not straight. That problem can not be fixed with ironing, you need to straighten. As far as getting wrinkles out I use steam and I always starch my fabric before cutting to give it stability. That works for me. I never prewash, just use color catchers and haven't had any problem.