Q: I bought an unlined copper preserving pot in Belgium many years ago. Is it safe to use for jams and jellies, or should I just use it to decorate my kitchen?
A: Copper is one of the best metals for conducting heat evenly, so cooks have used copper pans to cook jams for generations. particularly in France. Cooking jams quickly preserves fruit flavor.
However, copper also can leach out salts that can discolor foods, and too much copper in the diet can be toxic. That’s why most copper pots are lined with a nonreactive metal.
Unlined jam pots are safe as long as the mixture contains plenty of sugar. To be safe, mix the fruit and sugar before putting it in the copper pan, and don’t use the pan for sugar-free or reduced-sugar jams or for highly acidic foods like tomatoes.