(pi x radius x radius x peak) 2/ estimate the amount of one's mildew 3/ divide the amount of one's mildew by that of my mildew. you will get the quantity by which to multiply your components. See you shortly :) Hello Devi, I do not know potato starch. Maïzena in France is cornstarch. I can suggest you to go for cornstarch ideally. Here's a littl