Here is the starch recipe that Diane Gaudynski (
http://www.dianegaudynski.net/tips-april.htm) uses on her quilts.
Try my recipe for spray starch for all your pressing/piecing needs. Remember, you can adjust any of these amounts to suit your own needs, and also don't keep this for more than two weeks max. I make up a batch when I need it, then dump it out when I'm finished. It produces a super flat stable quilt: Dissolve half a teaspoon (or one teaspoon for a stiffer starch) of regular Argo cornstarch (in your cupboard probably) in a few tablespoons of cold water in a heat proof 2-cup measuring pitcher like Pyrex. Add boiling water to make one cup, stirring constantly. Then add cold water to the 2 cup line. Let cool and use in a pump spray bottle. Shake it every time you spray. You may have to dilute it a little if it is too thick or builds up white flakes. Lasts a week or so as there are no preservatives, no chemicals, no nothing that harms us or the environment, and it’s practically free, except for the spray bottle! Don't starch fabrics for storage as it will attract critters such as centipedes, and mice.