Can i use fabric softener instead of liquid starch?

1/2 cup cornstarch

1/2 cup cold water

mix and keep stirring while you pour in about 1 1/2 to 2 cups of boiling water depending on how stiff you need. It should stay clear.

Dip the item to be starched, wring and iron. (from the time of weekly wash days, wringer washers and flat irons)

My thoughts: Because it's food (cornstarch) this isn't good for long term projects as they'll rot eventually. Liquid starch is pretty cheap, doesn't go bad and there's 1000's of projects that use it. Finger paint is one that uses a lot of starch.