Clear Jel is a modified food starch (powdered form) that will not break down in high heat during processing. DON'T SUBSTITUTE!! Clear Jell is well worth the effort, it leaves a cleaner and thicker filling that is simply delicious. Kitchencraft (1-800-776-0575) in Waterville, IA sells it by the 1# ($3.25 + S&H) or 5# bags. Also sold by Bakers Catalog (King Arthur Flour) and also at http://www.homecanningsupply.com/. Oh, now that about does it, Amazon.com even sells the stuff!