In "Mastering The Art Of French Cooking: Volume Two," Julia Child wrote that one of the components home bakers need to make authentic French baguettes include creating a "simulated baker's oven." To create the steam, she instructs readers to place a hot brick into a "pan of water in the bottom of the oven."
Asbestos is a fibrous, fire-proof mineral that's been widely used for millennia in everything, including clothing, weapons, car parts, and floor tiles. As Child writes in her book, the asbestos floor tile seemed like the perfect hot baking surface "that added push of volume" to the loaves.
However, scientists discovered in the early twentieth century that asbestos exposure causes cancer. Child’s editor Judith Jones was at a dinner party in New York when she overheard a doctor discussing his research into cancer caused by asbestos and immediately realized they couldn't recommend the asbestos tiles anymore.
After a week of looking for a tile replacement, Child and her husband Paul settled on "ordinary red floor tiles," Child simply directed her audience to use the red tiles. Fortunately, home bakers today have an easy-to-find and safe choice for baking baguettes: King Arthur Baking says a pizza stone will work beautifully.