Why the Material of Your Loaf Pan Matters More Than You Think

I would like to say a word of appreciation for my glass loaf pan.

A little longer and leaner than the standard (it's 9 1/2 by 5—the dude on the far right in the photo below), it turns out the most reliably lush quick breads, be they yogurt, banana, or zucchini: Not only does the glass make it easy to keep tabs on baking status (because you can see the color of the exterior as the cake bakes), but I find that the finished product is more likely to slide out without a shorn bottom. Plus, the glass itself is easy to clean, with no schmutz-catching cracks and crevices.

But does my glass baking pan really do a better job at baking quick breads? And if so, why do metal pans seem to be more widely recommended? We conducted a mini-experiment to find out.

We baked three loaves of Dorie Greenspan's French yogurt cake in different pans: light metal, dark metal, and glass. Because the pans had slightly different dimensions, we split that batter into thirds by weight so that each one had the exact same amount. We generously buttered all three, then baked them in the same 350° F oven for 55 minutes.

And, as you'll see in the photo above, when the loaves came out of the oven, they all looked sort of... the same.

The real reveal came when we flipped the loaves over. Ready, set, gasp:

The loaf we baked in the lightest pan was the palest and most tender all over, with no distinctly hard, buttery crust, and it also suffered the most significant balding. Next came the loaf baked in the dark metal pan: It was less patchy, with darker and denser exterior. Lastly, the glass! The glorious glass. The cake practically slipped out of the pan (a dream!), no crumb left behind, and the entire bottom was an even shade of the deepest, most glistening gold.

But when we flipped the loaves right-side up and sliced into them, that aesthetic difference disappeared. Sure, the cakes baked in the darker metal pan and the glass pan had a slightly more distinct crispy crust (and some, like me, would argue that this is the best part of a quick bread). And they had less soft give—a finger pressed into the surface was met with more resistance.

But in the end, all the three slices were nearly indistinguishable. Was the loaf from the glass pan the tiniest bit drier in the center? I could not tell.

Yet most baking experts would advise against switching willy-nilly between loaf pans of different materials—and all those I consulted prefer light-colored metal pans to glass, and for good reason.

Why? Let's rewind to fourth grade-level science. Whereas metal is a conductor, glass is an insulator: It's slower to heat, but once hot, it does a better job of retaining that heat. And while that can result in more even baking (see the beautiful expanse of the bottom of the far-right loaf), it can also mean that the edges and bottoms—especially of a sugary cake—will brown too quickly, and sometimes before the inside has cooked through. Once out of the oven, your loaf will take longer to cool down (which might result in a slightly drier finished product).

The indomitable baking expert Alice Medrich told me she "NEVER" (her caps, not mine) uses glass pans because they overcook the sides and mess with the timing. She steers clear of dark metal pans for a similar reason (they'll absorb more heat than light-colored pans), and lines nearly all her loaf pans with parchment to prevent the outsides from overcooking (and for the sake of convenience).

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Rose Levy Beranbaum also relies on non-stick metal pans loaves to avoid over-browning. Plus, she finds that because the metal pans heat up more quickly, they're hotter "at the initial critical baking phase," which makes for a higher rise (especially important for yeasted loaves).

So why did our loaf baked in the glass pan end up looking so much better, especially from the bottom up? Erin McDowell—who, let it be known, also owns only metal loaf pans—had a smart theory: "People tend to scrub metal pans with the scrubby side of the sponge (or worse—steel wool or a green scrubbie to get off stubborn stuck stuff), which can seriously mar the finish (even on pans that aren't specifically 'nonstick')" and cause the bottom to stick. Glass, on the other hand, doesn't scratch as easily and, with its smooth surface, facilitates clean un-molding. A-ha! Might that be it?

Personally, I'll likely continue baking with my trusty glass pan until I see burnt edges and under-done insides. And if you, too, have a glass pan you know and loaf, you might consider a recommendation from the bakers at Ovenly in New York City: They suggest lowering your oven temperature by 25° F when baking in glass or dark-colored metal to compensate for the material.

And in the end, how bad can banana bread be, really?

Any experiments—baking or otherwise—you'd like to see us conduct? Tell us in the comments below.