First, I make my own starch for several reasons:
1. I can make it for mere pennies per batch
2. I can make it as strong or weak as I want for that particular project
3. No additives, preservatives or anything else to plague me, family members with allergies, or the environment
It's simply place 1 teaspoon corn starch (more or less depending on how stiff you want your fabric to be) in a 2 cup glass measuring cup and dissolve it with a little bit of cool water.
Carefully add one cup boiling water, stir for 30 seconds, then add 1 cup cool tap water. Stir for another 30 seconds.
When cool enough to handle, pour into a spritzer bottle and you're good to go!
This will last up to a week, and give a shake before each spritz.
I spray the starch on the wrong side of my fabric (just personal preference), let it sit for 30 - 60 seconds (sometimes longer if I get distracted doing something else in my quilt room
), then press the fabric.