I see a recipe for sizing has been posted already, so I'll just add trivia:
Here's another "remember when" for using starch...
Remember when nurses wore white caps, each different to identify their school of nursing?
The best way I knew to press my cap flat to dry after washing & starching was to smooth it over a clean refrigerator door. Then when it was dry, I'd peel it off the fridge & fold it into the cap shape.