Cake recipes often say to line the baking pan with waxed paper or parchment, as if the two were interchangeable. As liners for cake pans they are, but in many other ways, they are not.
Waxed paper is tissue paper that’s been coated with paraffin on both sides, making it greaseproof and moistureproof. It’s great for wrapping fatty or juicy foods, and its slippery, waxy surface means that gooey foods, such as candy and soft cheese, won’t stick.
Waxed (or wax) paper is neither heavy-duty nor all-purpose. It eventually lets liquids soak through, it tears easily, and it isn’t heatproof (the wax eventually starts to melt). But waxed paper can be used in the oven if it’s completely covered and protected from the heat. For example, waxed paper isn’t good for baking cookies because the exposed portions would smoke and char, but it’s fine at the bottom of a batter-filled cake or brownie pan.
Parchment is super-strong, even when wet. Parchment is made by running sheets of paper through a sulfuric acid bath, a-process that makes the paper strong even when it gets wet or hot. The surface of parchment, also called sulfurized paper, is hard, smooth, and impermeable so it won’t soak up grease or moisture. Many manufacturers also apply a silicone coating to make it entirely nonstick, which is why this kind of parchment is sometimes called silicone paper.
Parchment is ideal for wrapping moist foods, for cooking en papillote (where the paper needs to hold up even when filled with steam), and for cutting a makeshift lid for a skillet to trap the moisture of vegetables cooking on the stovetop. It’s also a terrific baking pan liner because it can withstand high temperatures and because it’s nonstick.
While parchment is more expensive than waxed paper, it can be a better value since it’s so versatile and, unlike waxed paper, it’s reusable as a pan liner. You can buy rolls of parchment in supermarkets, but I prefer to use sheets of parchment (sold in restaurant-supply stores) because they don’t curl up.