Now, the age old ? of washing fabric before using it. Dipping or painting unwashed fabric can cause it to shrink unevenly. I know this from experience.
I always wash & damp dry fabric first. This gets the fabric to an evenly shrunk state and then starch any way you like. When I dip I use 50/50 and just hang to dry. I also spray sometimes and press dry. Always let the starch soak into the
fabric before pressing to avoid flaking.
peace