A lot of cooks use aluminum foil to create a better seal between lid and pot during braising, Chemicalkinetics notes on Chowhound. But when foil comes into contact with the cast-iron edge of enameled Dutch ovens like those from Le Creuset, will it hurt your pot or create an adverse reaction in the food, ILuvGrub asks?
Absolutely not, says dixiegal, who uses foil with bare cast-iron pots all the time. MikeB3542 agrees: Foil should pose no problem at all for short-term contact with cast iron, enameled or not. "I always line my camp ovens with aluminum when cooking particularly messy dishes," MikeB3542 says—it makes cleaning up a snap, no bad reactions observed. After months or years of contact, there could eventually be a reaction, but even the hours to slow-cook a roast just aren't enough time to cause harm to your cookware.
But apart from lining with foil for easy cleaning, sealing a heavy pot might be a waste of time in the first place, MikeB3542 says. A cast-iron pot with a tightfitting lid should create enough of a seal to braise beautifully, no help necessary.
Discuss: Cast iron and tin foil