Testing Glass Food Storage Containers

We put these glass containers through the same series of rigorous tests as our lineup of plastic containers, with the exception of knocking them onto the floor and with the addition of using them in the oven. Our goal was to find a truly airtight, leakproof container, in a size and shape that works well for home cooks, that resists stains and odors, can reheat food in both oven and microwave, and is easy to use and clean.

Are Glass Containers Really Airtight?

To keep food at its freshest, you want a container that is airtight and leakproof. If it tips a little in a crowded refrigerator or while you're transferring it from one location to another, you want to be sure it won't spill. And if you happen to be storing very fragrant food, odors shouldn't escape the container. We tested seal quality by filling our containers with water and shaking them in all directions, as well as by submerging them in water with moisture-detecting crystals sealed inside. One failed both tests right away: Its plastic cover lacked the silicone gasket and flaps that most others had to secure the lid, so it simply didn't seal completely. The rest performed perfectly—at least the first time we did this test. But after we'd used and washed them during routine testing and run them through the dishwasher 50 more times to simulate a year of weekly use, two of the four models failed to seal as tightly when we repeated the test, indicating that they might not hold up well over time.

To check whether they would retain smells, we filled the containers with oil-packed tuna and anchovies, refrigerated them overnight, washed them carefully, and conducted a “sniff test.” Only the container that had failed our leak tests, with its loose plastic lid and no gasket, was mostly odor-free; the others revealed the importance of removing and scrubbing gaskets and around lid flaps, whose nooks and crannies were prone to trapping smells. (Two containers' gaskets were large, soft, and easy to pull out; the third was tiny and difficult.) To see if they'd stain, we loaded the containers with chili full of tomatoes and colorful spices. After refrigerating the containers over a weekend, we microwaved the chili still in the containers to a piping-hot 160 degrees. Unlike the plastic containers we tested, these glass versions stayed stain-free, but their plastic lids, which sat atop the chili, did become lightly stained. One container's bright blue lid cleverly masked any stains. The container with a glass lid showed stains on its white silicone trim, but these eventually disappeared with more scrubbing.

Snapping Plastic Lids onto Glass Containers

We opened and closed each container 200 times, 100 times before and 100 times after our dishwashing tests, reversing the lid position each time. This helped us evaluate how easy each container was to seal and the durability of its construction. None of the lids broke, but some were definitely much easier to seal than others. The worst had extremely tight flaps that snapped down over a raised ridge on the glass bottom. That tight seal never leaked a drop, but it was a little painful for some testers to close. Two others—the one with the simple plastic lid and the glass lid with silicone trim—were easy to put on, but they rarely felt as securely latched as those with snap-down flaps; in fact, these two were the ones that leaked throughout testing. Ultimately, we preferred containers with snap-down flaps and silicone gaskets, and our top choice was comfortable to snap while remaining securely leakproof.

Using Glass Containers in the Oven

All the glass food storage containers we tested claimed to be ovensafe, a nice bonus that makes them more versatile. However, every product's label and/or website listed extensive warnings about thermal shock, which is when rapid, extreme temperature changes cause glass to shatter. We recommend that you read these instructions carefully before using your container in the oven. In every case, you should put glass vessels into only a fully preheated oven, since ovens preheat unevenly, with much hotter and cooler zones forming until the oven reaches its target temperature; also, never use them under the broiler. While three of the five containers are made of borosilicate glass, a material that is supposed to be more thermal shock–resistant than the tempered soda-lime glass of which the other two were composed, their warning lists were equally long. We used each model, in a preheated oven, to warm up refrigerated macaroni and cheese to serving temperature and had no problems heating or handling any of the containers.

At the end of testing, we had a clear winner. The OXO Good Grips 8 Cup Smart Seal Rectangle Container ($14.99) sealed easily and tightly without letting a drop spill. Its large, soft gasket was easy to remove, clean, and replace, and it emerged from testing in excellent condition. It's our new favorite glass storage container. While we tested the 8-cup version, this model comes in a wide variety of sizes and is sold a la carte and in sets.

Winning Traits

• Airtight and leakproof

• Lid that is easy to open and close but seals snugly and tightly and stands up to abuse

• Generous 8-cup size

• Large, easy-to-remove silicone gasket for simpler cleaning, with large channel that makes it easy to clean

• Safe for use in dishwasher, freezer, microwave (with lid flaps open), and preheated oven up to 450 degrees

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