Why You Should Use Glass Food Storage Containers

Affordable options for years of use.

tupperwares from above
Photo: Michael Hession

We’ve tested dozens of food storage containers over the past three years, subjecting them to repeated freezing, microwaving, and 3-foot drops onto hard floors. If you want glass (which is odor resistant and oven safe, though heavy), we recommend the durable Pyrex 18-Piece Simply Store Food Storage Set. For plastic (which is lighter and shatterproof), we recommend getting the leakproof Snapware 18-Piece Total Solution Plastic Food Storage Set. Both are affordable options that will provide you with years of use.

Our pick: Pyrex 18-Piece Simply Store Food Storage Set

Pyrex tupperwares
Photo: Michael Hession

Because they’re made of tempered glass, the sturdy containers in the Pyrex 18-Piece Simply Store Food Storage Set survived our counter-height drop tests onto wood without breaking. The lids from this set were easier to close than any of the others we tested. And although the set’s rectangular containers aren’t leakproof, we were surprised to find that its round containers are. However, because the lids don’t clip closed like our runner-up pick’s, the Glasslock containers, we’d exercise caution if you plan to use the Pyrex containers to transport liquids. This set stacks neatly and is microwave, oven, freezer, and dishwasher safe.

BUY: Pyrex 18-Piece Simply Store Food Storage Set
$30, Amazon

Our pick: Snapware 18-Piece Total Solution Plastic Food Storage Set

snapware tupperware
Photo: Michael Hession

The containers in the Snapware 18-Piece Total Solution Plastic Food Storage Set stayed sealed in our drop tests and sustained only minor cracks on the edge of the lid after repeated drops from waist height. This set was also able to keep stains and smells from lingering and looked great filled with leftovers and stacked in the fridge. The containers nest well, too, so they take up less space in a cupboard than much of the competition.

BUY: Snapware 18-Piece Total Solution Plastic Food Storage Set
$20, Amazon

Runner-up: Glasslock 18-Piece Container Set

Glasslock tupperware
Photo: Michael Hession

The Glasslock 18-Piece Container Set was our former top pick for glass, and survived multiple drops from counter height. But after three years of long-term testing, some of the containers have chipped around their edges. That said, if you’re looking for leakproof glass containers for meal prep, these are the best we’ve tested. These containers also keep food fresher longer than any other set we’ve tried. However, their locking lids require more effort to close than our main pick, the Pyrex 18-Piece Simply Store Food Storage Set, and we suspect that the repeated stress of snapping them shut is what caused some of our containers to chip. The Glasslock set comes with a variety of shapes that store nicely in the fridge, and the containers are safe to use in an oven, microwave, freezer, or dishwasher.

BUY: Glasslock 18-Piece Container Set
$36, Amazon

Budget pick: Rubbermaid TakeAlongs 40-Piece Storage Set

Rubbermaid tupperware set
Photo: Michael Hession

The Rubbermaid TakeAlongs 40-Piece Storage Set is perfect for transporting food to parties and other functions, and because it’s so cheap, you won’t mind leaving pieces behind. This set comes in a variety of sizes ranging from ½ cup to just over 6 cups, with containers that stack well for convenient storage. They slightly hung onto scents and stains after washing, but they were some of the only cheap containers we tested that didn’t leak.

BUY: Rubbermaid TakeAlongs 40-Piece Storage Set
$19, Amazon

Why you should trust us

In reporting this guide, we talked with several experts: Nancy Hopkins, senior deputy food and entertaining editor for Better Homes and Gardens; Faith Durand, executive editor for The Kitchn; and Michele Thomas, who was the executive editor at the International Culinary Center at the time (and is now a sales associate and social media manager at The Greene Grape). We asked our science editor, Leigh Krietsch Boerner, PhD, to review recent research on the safety of plastics for this guide’s update. Additionally, we reached out to glass experts such as Jane Cook, PhD, chief scientist at the Corning Museum of Glassin Corning, New York, and William C. LaCourse, PhD, a professor in the glass engineering department at Alfred University in Alfred, New York.

We also consulted reviews from Cook’s Illustrated (plastic and glass containers; subscription required), Good Housekeeping, and The Daily Meal. Finally, we looked for highly rated sets from stores such as Target, Walmart, Macy’s, The Container Store, and Amazon.

Ganda Suthivarakom, who wrote our original guide, has spent dozens of hours researching and testing (including filling, shaking, storing, freezing, microwaving, washing, and dropping) food containers. Michael Sullivan, who contributed to our subsequent updates, has reviewed wine glasses and dinnerware sets, as well as other kitchen items for Wirecutter. For this guide, he tested food storage containers for several months.

Who should get this

If you use old plastic yogurt containers or takeout containers for basic food storage, you have a few reasons to upgrade. First, you can’t see through yogurt containers, so once the lid is on, you can easily forget about what you have in there (and let it rot). Second, they aren’t leakproof, which means that transporting them to work for lunch can be a messy affair. Third, such plastic containers are not FDA-approved for repeat food storage or microwaving. Upgrading to more durable glass or plastic food storage containers means they’ll last longer and keep your food fresher.

If you’re getting into meal prep (that is, portioning individual meals into separate containers to eat throughout the week) you may want an extra set of containers just for that. Our plastic recommendations are especially great for meal prep because they’re less expensive and light enough to carry to work. If you already own a glass or plastic container set but want something that you can bring to potlucks and picnics, you also might want to purchase a cheap plastic set that you won’t mind leaving behind.

Choosing between glass and plastic containers

Wondering which material to get? Here’s how we’d decide.

Choose glass:

• if you don’t mind heavier containers that can shatter
• if you’re using the containers mostly for storage at home
• if you store foods that tend to stain or smell
• if you prefer oven-safe containers

But choose plastic:

• if you want something that won’t shatter
• if you want a cheaper option that you can leave at potlucks or stock up on for meal prep
• if your family tends to lose containers
• if you want something lighter to carry around

Ultimately, the choice between plastic and glass is a personal one based on lifestyle. One of the main issues to consider is breakage. Most glass food storage containers are made of tempered glass, which is more durable than regular non-heat-treated soda-lime glass. However, glass is glass, and it can still shatter if you abuse it. Plastic containers won’t shatter if they break, so there’s less risk of cutting yourself. Nancy Hopkins, senior deputy food and entertaining editor for Better Homes and Gardens, said, “We tell people to do your homework, read the directions, wash it and store it properly. Do what’s easy and convenient for your life.” Her preferred food storage container is the self-sealing plastic bag, for its versatility and the fact that you can lose them, which can be important in a household with kids. “My two girls did not like plastic or glass containers. They wanted things they could throw away.” Michele Thomas, the former executive editor at the International Culinary Center, prefers plastic because it’s “easy to get, easy to transport, and easy to store, especially in a small apartment.”

Faith Durand, executive editor for The Kitchn, stores her food in glass. She told us, “A few years ago I got rid of my old, mismatched plastic storage ware and switched almost entirely to glass containers. I find that the lids fit better, and I am more comfortable storing food in glass instead of plastic. I also like how easy it is to see what’s inside. So I use glass for nearly everything.”

So, some experts prefer glass and some prefer plastic. The choice is yours, too.

A word on tempered glass

Most glass food storage containers are made of tempered glass, a type of heat-treated soda-lime glass. Tempered glass is ideal for the job because it’s very durable and able to withstand high temperature changes. It does have one downside: on rare occasions, it can break unexpectedly. That being said, it’s often referred to as “safety glass,” because when it does break, it crumbles into cube-shaped pieces rather than long, thin shards. (This is why tempered glass is used for side and rear windows in cars and glass shower doors.)

The reason tempered glass can break unexpectedly has to do with how it’s made: When glass is heat-tempered, the exterior is force-cooled so it solidifies quickly, leaving the center of the glass to cool more slowly. As the inside cools, it pulls at the stiff, compressed outer layer, which puts the center of the glass in tension. As Jane Cook, PhD, chief scientist at the Corning Museum of Glass, explained, “The atoms in [the tensile area] are stressed and they’re trying to pull themselves apart. But they can’t as long as they’re balanced by compression on the outside.” That balance makes the glass stronger, but if it’s thrown off—if the tensile region is disrupted by surface damage, manufacturing flaws, or extreme thermal stresses—the glass can spontaneously shatter. However, according to our experts, spontaneous fracture in tempered glassware is pretty rare, particularly if you take good care of your glassware. (A more detailed explanation on how tempered glass shatters and how to help prevent it from happening is at the end of this guide.)

Other types of glass

Some food storage containers are made from borosilicate glass because it’s resistant to thermal shock. However, it’s more brittle than tempered glass and more expensive. Heat-strengthened glass has a lower surface compression on the exterior of the glass than tempered glass, so it’s not as resistant to sudden changes of temperature. You’re unlikely to find non-heat-treated soda-lime glass containers because they are neither oven nor freezer safe.

How we picked and tested

Whether choosing glass or plastic, a good container should be airtight, leakproof, break resistant, stain resistant, and easy to clean and store.

“If you’re going to use a container, you want something that’s really airtight with a good seal if it’s something you plan to keep for a bit,” Nancy Hopkins, senior deputy food and entertaining editor for Better Homes and Gardens, told us. Not only will a good seal help food last longer, but leakproof construction is also important for transporting liquids. Many of the models we tested had a gasket seal around the lip and plastic hinges that snap shut so you know the container is sealed properly. A removable gasket makes cleanup easier (and will help avoid mold buildup), because you can remove it and wash it separately.

We followed the advice of Woman’s Day and chose square or rectangular containers over round ones in order to maximize fridge space. Nesting and stackability are nice to have, as are interchangeable lids for different sizes. We tried to pick sets with a good range from large to small, with emphasis on rectangular or square space-saving shapes; we didn’t eliminate round shapes, though, as they can be good for liquid foods.

The containers should be clear or easy to see through so you know what you have inside without opening them. For this reason, we avoided ceramic containers (which can also break easily).

Microwave vents on the lid are a silly feature we avoided; it’s just another piece to de-crud, and you’re better off removing the latches and resting the lid on top of the container in the microwave (or not using the lid at all, as some manufacturers suggest).

Resistance to stains and odors is key (you don’t want to smell or see yesterday’s lunch on your container). We also wanted something that could go in the dishwasher and the microwave, which eliminates stainless steel.

Plastic or glass storage containers range from about $3 to $10 apiece. Containers in a set are generally less expensive per piece. Although price was a factor when we made our pick, glass containers will last a long time, so price was not as big of a concern as you might think.

The sets we looked at provided the best value per piece. Keep in mind that most manufacturers include both the containers and lids in the total set count. So if a set is sold as 14 pieces or 16 pieces, you’re really getting only seven or eight containers.

assorted tupperware
We tested glass and plastic food storage containers.
Photo: Michael Hession

We tested food storage containers by filling them with water and shaking them, both before and after they had run through the dishwasher. To test how the containers would react to smells and stains, we filled them with tomato sauce, placed them in the freezer for three days, and reheated the sauce in the microwave for two minutes. We also froze quarter-pound portions of ground beef for two weeks to look at freezer-burn patterns. And, most fun of all, we conducted a drop test from waist height for all of the picks (including our glass containers) to see if they would break or if the lids would pop off. We did our drop test on a piece of wood placed over cement in an attempt to simulate a non-bouncy kitchen floor. In our initial tests, we also tracked how long food stayed fresh in the containers by refrigerating fresh, cut strawberries for about two weeks.

For our 2018 update we also subjected the glass sets to extreme thermal stresses (which we strongly do not recommend trying at home): we pulled the containers from the freezer and filled them with boiling water; we took containers that had been in a 350 ºF oven for 10 minutes and filled them with ice water; we used the containers to reheat cold beef stew and tomato sauce in the microwave for three minutes; and finally, we froze beef stew in the containers and put them directly into a 350 °F oven for 10 minutes.

Our glass pick: Pyrex 18-Piece Simply Store Food Storage Set

The Pyrex 18-Piece Simply Store Food Storage Set is the best glass container set we’ve tested. Made from tempered glass, these containers survived multiple counter-height drops onto wood without breaking. Though not all of the lids are watertight, they’re faster and easier to seal than the lids of our runner-up pick, the Glasslocks, which require more force to clip closed. And because each shape of lid is a different color, they’re easy to match to their corresponding containers. This set stacks neatly and is microwave, oven, freezer, and dishwasher safe.

We were impressed with the durability of the Pyrex containers and their lids, which survived drop after drop onto a wood board placed over a cement floor. At one point, a container missed the board entirely and bounced off the cement without breaking. The containers also passed our thermal stress tests: they were unfazed after transferring them directly from a 350 °F oven to the freezer and vice versa (we strongly urge you not to try this experiment at home).

Pyrex tupperware
Our testers found the color-coded Pyrex lids easy to seal.
Photo: Michael Hession

The Pyrex lids were easier to seal than Anchor Hocking’s similar press-on lids and Glasslock’s press-on ones. The lids on the round containers we tested are watertight, but we found that the rectangular containers leak from the corners. However, because you’re more likely to store soups and stews in the round containers, we’re willing to forgive this minor drawback. In our tests, we could detect a slight tomato aroma after running the Pyrex lids though the dishwasher, but the smell wasn’t as strong as the one left behind on some of the other containers we tested. Pyrex’s plastic lids are obviously not oven safe, and if you’re using a dishwasher to clean the lids, they should be placed only on the top rack.

The Pyrex set includes nine glass containers with matching lids ranging in size from 1 to 7 cups. If you’re looking for fewer containers, the Pyrex Simply Store line is also available as a 14-piece set (with seven containers and accompanying lids). You can purchase replacement tops on Pyrex’s website. Pyrex offers a two-year warranty on the Simply Store containers, meaning the company will replace defective pieces from the set as long as they haven’t been subjected to misuse or abuse. Also, according to Pyrex, they’ll replace any glass product that breaks due to oven heat. If this happens, just be sure to keep the damaged item, as you may be asked to return it. Contact the Pyrex Customer Care Center for returns or replacements.

Glass pick: Flaws but not dealbreakers

Like the other glass containers we tested, the Pyrex set has a number of visible flaws in the glass. (For more information on how these flaws can affect glassware, see here). These flaws aren’t noticeable unless you’re looking for them, but it’s something to know before you buy.

As mentioned above, not all of the containers in this set are leakproof, so these are not the best option for prepping meals to bring to work or school. Though the round containers didn’t leak any water in our tests, we’d still exercise caution if you intend to use them to transport liquids. Our runner-up pick, the Glasslock, is best if you’re looking for an entirely leakproof glass option.

All tempered glassware runs the risk of spontaneously shattering (albeit very rarely) and the Pyrex containers are no exception. Glass is a brittle material and needs to be treated with care.

BUY: Pyrex 18-Piece Simply Store Food Storage Set
$30, Amazon

Our plastic pick: Snapware 18-Piece Total Solution Plastic Food Storage Set

If you or other members of your family are prone to losing containers, or you simply prefer plastic over glass, we recommend the Snapware 18-Piece Total Solution Plastic Food Storage Set. This set doesn’t offer the same durability as Pyrex, but it’s cheaper, lighter, and more convenient for transporting food. For those reasons, we think it’s the best option of our picks for those interested in meal prep.

The lids in the Snapware Total Solution set are easy to snap closed, unlike those of the Snapware Airtight set, which were difficult to latch and repeatedly popped open. The Snapware Total Solution containers and lids provided a tight seal that didn’t leak (even after a run through the dishwasher). Our testers were surprised that the containers didn’t retain any discernible food stains or smells, which wasn’t the case with the Popit containers or the Snapware Airtight set we recommended in 2015. The Snapware Total Solution set performed admirably in our drop tests: only a small piece on the corner of the lid broke off after the third drop.

Our testers liked the colorful gaskets on the lids, which they found easy to identify and match to the corresponding container. (Also, the orange lids for the round containers and the aqua lids for the rectangle containers work with the glass Snapware, which is convenient if you’re buying both glass and plastic.)

Snapware offers a lifetime warranty on both the plastic containers and lids if “damaged during normal household use.” If you need to make a claim, call World Kitchen and be sure to keep the container or lid, as you may be asked to return it.

Plastic pick: Flaws but not dealbreakers

Like the glass version of this set, the gaskets aren’t removable, which makes cleaning more difficult compared with the Glasslock set.

BUY: Snapware 18-Piece Total Solution Plastic Food Storage Set
$20, Amazon

Runner-up: Glasslock 18-Piece Container Set

We recommend the Glasslock 18-Piece Container Set only if you want a glass set that’s leakproof. It used to be our top pick for glass storage, but it’s now our runner-up because some of our containers chipped during long-term testing, and we’ve heard from other people who have had the same issue. The Glasslock containers’ tight-fitting lids keeps food fresher longer, but they also put pressure on the edge of the glass, which, according to the glass experts we spoke to, may be causing stress that results in breakage. That said, compared with other brands we tested, the Glasslock containers locked more securely without leaking and didn’t break or pop open when dropped.

The Glasslock set comes with square, rectangular, and round containers ranging from 0.73 cup (173 ml) to 6.3 cups (1.5 L) in size. The walls are thick but perfectly see-through, and same-shape containers nest even with the lids on. Like Pyrex and Anchor Hocking, Glasslock makes its containers of tempered soda-lime glass that are oven, microwave, freezer, and dishwasher safe. These containers stack beautifully in the fridge, making it easy to see what leftovers are awaiting you.

The plastic top, labeled #5 for polypropylene, has a firm silicone gasket that fills the lid groove from edge to edge and provides a tight seal that doesn’t leak. Our testers found that the plastic flaps on the lids were more difficult to close than the lids on the Pyrex glass containers, which were easy to press on. However, the Glasslock containers kept food fresher longer than much of the competition. In our tests, greens remained sprightly and cut strawberries tasted just a touch off after refrigerating for two weeks. Tomato sauce didn’t impart stains or smells to the glass or to the plastic lid. Frozen ground beef smelled and looked fine after two weeks in the container, but it had some minor freezer burn on the surface.

Impressively, the Glasslock set bounced in our drop tests with no damage to the glass container. The lids remained perfectly intact and didn’t pop off. (For kicks, we even tried dropping a Glasslock container onto cement. It broke on a corner only after three other attempts to crack the thing.) The glass Snapware set we tested didn’t fare as well in our drop tests: some of the flaps opened, and the corner of the lid cracked.

Glasslock will replace any faulty lids free of charge within three years from the date of purchase (regardless of where you buy them), shipping costs not included. Be sure to save your receipt as proof of purchase. The Glasslock customer service representative we spoke with said the company will replace glass containers (if they break during normal use) for up to one year. If you buy your set directly through Glasslock’s website, the company will offer a full refund within 30 days of purchase as long as the containers are unused and in their original packaging.

Glasslock tupperware with blueberries
The plastic flaps on the Glasslock lids are more difficult to close than the lids on our main pick.
Photo: Michael Hession

Runner-up: Flaws but not dealbreakers

Like all tempered glassware, the Glasslock containers can spontaneously shatter (albeit very rarely) due to surface damage, manufacturing flaws, or extreme thermal stresses. Beyond that, several pieces we’ve long-term tested have chipped around the edge, and we’ve heard other people complain of the same thing. The chipping is probably due to the pressure that the locking lids put on the glass when you snap them shut. William C. LaCourse, PhD, a professor in the glass engineering science department at Alfred University, told us, “There will be stresses as a result of the cap and putting the cap on with fairly high pressure … it essentially squeezes the cap onto the glass.” He explained that if there are any minor flaws already present in the glass, the added pressure from the lids could cause the containers to chip or break.

We’ve also noticed some negative Amazon reviews related to breakage that occurred during shipping. To research this problem further, we decided to order four of the same Glasslock sets from different retailers: Amazon, Walmart, Sears, and Glasslock. All of the sets arrived well-packaged except for the set we purchased through Sears, which used Amazon’s Fulfillment By Amazon service to deliver the order. (The set arrived directly in the product box with no additional packaging.) Interestingly, the set we ordered directly through Amazon was well-packed with bubble wrap. But regardless of how they were packaged, none of the sets we purchased arrived broken. We also subjected the Glasslock containers to extreme thermal stresses, and they survived unscathed.

If you’re committed to getting the Glasslock containers because you want a glass container that doesn’t leak, we don’t think the concern of chipping or breakage should stop you. Only a small number of the containers we’ve tested have chipped. Just keep an eye out every time you open a container: the only thing you don’t want is a piece of glass in your food. And if you’re going to choose glass over plastic, keep in mind that all glassware is inherently brittle and needs to be handled with care.

If you don’t have a dishwasher, you may find gross black mold growing behind the gasket on the Glasslock lids. (This seems to happen only to sets that people handwash.) To prevent this, take out the light-green gasket from time to time (use a butter knife to dig it out so you don’t nick it) and wash it with hot water, letting it dry completely before you reassemble the lid.

Some Amazon reviewers have complained that the flaps on the lids of the Glasslock containers make a racket when snapped shut. However, we don’t think this is a dealbreaker, because it’s just a split second of noise.

BUY: Glasslock 18-Piece Container Set
$36, Amazon

Budget pick: Rubbermaid TakeAlongs 40-Piece Storage Set

If you need a dirt-cheap set that you can leave behind at picnics or potlucks, the best of those we tested was the Rubbermaid TakeAlongs 40-Piece Storage Set. This set came with more size options (ranging from ½ cup to just over 6 cups) and containers than any of the other flimsier sets we tested. Although it has a lot of lids to keep track of, this set stacks well and doesn’t take up as much space in a cupboard as you’d expect.

The Rubbermaid TakeAlongs aren’t perfect, because they’re not intended for long-term use.

Unlike the Ziploc and Glad containers, the Rubbermaid TakeAlongs didn’t leak before or after running through the dishwasher. It was also the only set that didn’t explode when filled with water and dropped from waist height onto wood. In our tests, the Reditainer and Glad containers shattered and splashed water and broken bits of plastic everywhere. The Rubbermaid’s lid remained sealed for two drops and the base cracked only after the fourth drop.

Rubbermaid set
The Rubbermaid TakeAlongs have containers and lids that nest well for convenient storage.
Photo: Michael Hession

Like all disposable sets, the Rubbermaid TakeAlongs aren’t perfect, because they’re not intended for long-term use. The plastic becomes soft when microwaved, though not as soft as the Ziploc and Glad containers. The Rubbermaid TakeAlongs also stained slightly and retained a faint tomato scent after dishwashing, which was a problem we encountered with all of the cheap plastic sets we tested. However, because this set is so affordable, has a variety of container sizes, and doesn’t leak, we’re willing to forgive these drawbacks.

BUY: Rubbermaid TakeAlongs 40-Piece Storage Set
$19, Amazon

What about BPA in plastic containers?

We once worried about BPA (bisphenol A) in plastic, but we don’t anymore. You can find countless articles online proclaiming the evils of plastic, and this guide used to be one of them. On the basis of the data available to us at the time, we warned against plasticizers (the additives used to make plastic moldable) possibly leaching out as a result of heat or wear and tear, causing endocrine disruption (hormonal changes that can be bad for your health).

However, in 2015 the European Food Safety Authority released a large-scale risk assessment that convinced us that we should stop fearing plastic. We trust the EFSA because it has more stringent rules than the US Food and Drug Administration, and because it conducted a comprehensive study of BPA occurrence in food-contact materials with about 3,600 results. More than 3,100 of those results came from governmental tests (not industry-funded studies), and 400 results came from academia (with, yes, some industry-funded results in the mix but not many). Finding another study of plastic that comes close to this kind of scrutiny would be hard.

As we’re fond of repeating ad infinitum, the dose makes the poison, and in the case of food-contact plastic, BPA consumed at current levels is safe: “EFSA’s comprehensive re-evaluation of bisphenol A (BPA) exposure and toxicity concludes that BPA poses no health risk to consumers of any age group (including unborn children, infants and adolescents) at current exposure levels. Exposure from the diet or from a combination of sources (diet, dust, cosmetics and thermal paper) is considerably under the safe level (the ‘tolerable daily intake’ or TDI).” Even after lowering the amount allowed from 50 micrograms per kilogram of body weight per day down to 4 micrograms, the EFSA said, “The highest estimates for dietary exposure and for exposure from a combination of sources (called ‘aggregated exposure’ in EFSA’s opinion) are three to five times lower than the new TDI.”

None of the containers we looked at have BPA; for the most part, container manufacturers have phased it out of food-contact plastics because of the bad rap it’s received in the media. And although other, less widely studied plasticizers are still in use, particularly BPS (bisphenol S) and BPF (bisphenol F), which have been phased in to replace BPA, if they leach into food in the minuscule amounts that BPA does, we’re not worried.

And phthalates are not generally used in food storage containers.

Even with heat, the levels of plasticizers that leach into food are very, very low. Wirecutter’s former science editor, Leigh Krietsch Boerner, spoke to Neal Langerman, principal scientist and owner of the consulting firm Advanced Chemical Safety. He told us that the aging studies that companies do on plastics mimic about five or six years of use, but that the amount of plasticizers that would presumably be consumed is well below what would actually cause harm, according to the available data.

Why is my tempered glassware spontaneously shattering?

We’ve read customer reviews on Amazon and feedback from our readers who have occasionally reported that their tempered glassware “spontaneously shattered.” Even though tempered glass is more durable than non-heat-treated soda-lime glass, it’s still brittle and prone to breaking. What’s unique about tempered glass is that is has stored energy in the glass that causes it to crumble into tiny cube-shaped pieces when it breaks (unlike soda-lime glass, which breaks into shards). As mentioned above, it’s intentionally designed to shatter in this manner as a safety precaution. Sometimes tempered glass can spontaneously break, seemingly out of the blue (the glass experts we spoke to stressed that this occurrence is very rare). Several contributing factors can cause tempered glass to spontaneously break, but the most common culprits are: surface damage, manufacturing flaws, and extreme thermal stress. Often, it’s a combination of several of these factors that cause glassware to break under the right conditions. Anything that disrupts the tensile area of tempered glass will cause it to break.

Surface damage caused by the rough treatment of glass (such as repeatedly scratching, dropping, or banging glass against another glass in the dishwasher), can contribute to the development of subcritical crack growth, which can ultimately lead to breakage. LaCourse said, “The glass may not break immediately, but … it can fail at a much later and essentially unpredictable time. It would be rare–usually it would fail immediately, but it could be delayed by months.”

Thermal stress is another factor that can cause glass to spontaneously break. Cook told us, “Temperature itself isn’t what causes stress. It’s a difference in temperature from one part of the glass to another part of the glass. If one part is expanding or contracting more or less than the other at the region in between, that’s where the stress happens. It’s literally ripping itself apart. And if there happens to be a critical flaw in that region of higher stress between the hotter and the colder area, that’s where it’s going to break.” In other words, don’t test the limits of a tempered glass container by taking it from the freezer and placing it directly into a hot oven (or vice versa).

Manufacturing flaws are imperfections in the glass that develop during the manufacturing process. These flaws can weaken the structure of glass and make it more prone to breakage. Each of the following manufacturing flaws can contribute to breakage in tempered or untempered glass:

• Stones: small, unmelted sandy particles in the glass.
• Seeds: gas bubbles trapped in the glass.
• Blisters: gas bubbles that have broken through to the surface of the glass.
• Cord: striations or rivulets running through the glass (according to Cook, cord is less likely to contribute to stress, but it can if it’s severe).

You can extend the lifetime of your glassware by treating it with care. Cook said, “Glass is inherently brittle and has a certain amount of unpredictability in it. All glass has that unpredictability. The tempering is an attempt to reduce the unpredictability, but it is not perfect.” If the disadvantages of tempered glass outweigh the advantages for your lifestyle, we recommend using plastic food storage containers.

Care and maintenance

It’s tempting to just leave the lids on when you microwave stuff in your containers. Don’t. No sealed lid benefits from the vacuum effect that happens when you heat your food in the microwave. Abusing the lid in this way can cause it to warp and lose its seal. When you microwave, if you must keep the lid on to prevent splatter, always make sure to loosen the lid completely and set it slightly ajar across the top of the container. An even better option is to use a vented microwave cover or a paper towel over your container when you zap it. Also, if you’re using a microwave with sensor reheat, it won’t work properly unless it can detect the amount of moisture coming off of your food.

Handwashing works fine for most food storage containers. When you’re loading these into the dishwasher, plastic pieces should always go on the top and glass pieces can go on the bottom rack. If the lid has a removable gasket, remove the gasket from time to time and clean it separately from the lid to make sure no mold can grow.

gasket on tupperware
If the lid has a removable gasket, remove it using a butter knife. Wash and dry the gasket thoroughly to prevent mold from growing.
Photo: Michael Hession

If the lid has a removable gasket, remove it using a butter knife. Wash and dry the gasket thoroughly to prevent mold from growing. Photo: Michael HessionDry the lids completely before storage, and leave the lids resting on top of the containers, but not snapped shut, which helps to protect the longevity of the seal.

After removing glass food storage containers from a hot dishwasher, the experts we spoke to recommend letting them cool before stacking them in a cupboard. LaCourse said, “When they’re hot and clean, they will scratch easily.” Hot glass will also be more prone to sticking. Cook explained that, “When they’re warm, they’ve expanded slightly. As they cool down, if you put a colder glass inside of a warmer glass, they’re just going to grab onto each other. So you’re more likely to get a glass stuck inside another glass, and it needs to be pounded out or put under running water in order to get them apart, which all leads to more surface damage and shorter lifetime.”

Also, never subject your glass food storage containers to extreme thermal stresses (such as taking containers from the freezer and placing them directly into a hot oven and vice versa). Always stay within the recommended temperature threshold indicated in the manufacturer’s instructions.

The competition

Glass sets

The Snapware Total Solution Pyrex Glass Set was our former runner-up pick for glass containers. Like our current runner-up pick, this set’s lids clip closed and may subject the lip of the containers to stress that can increase the chances of breakage. Because the silicone-bordered lids are a little harder to clean by hand, we recommend the Glasslock containers instead.

The Anchor Hocking Glass Food Storage Set survived our drop tests, but its containers leaked more than the similarly designed glass Pyrex containers we tested. The flimsy lids in this set also held onto odors more than our picks.

The OXO Good Grips 8 Piece Smart Seal Glass Rectangle Container Set is one of the few sets we looked at that’s made with borosilicate glass, which is a great material for withstanding temperature changes. However, it’s expensive (about $7 per container) and comes with only four containers, and one of the flaps completely broke off of a lid on our first attempt to close it.

The Zyliss Fresh Glass Food Storage Containers are also made of borosilicate glass, but are more expensive than our current top pick.

The Pyrex 6-Piece Glass Rectangular Storage Set leaked quite a bit (some customer reviews also report this). During our drop test, the lids loosened multiple times, allowing the contents to spill out. The No-Leak lids, which come with a vent for lid-on microwaving, seemed to warp a bit after the microwave and dishwasher run.

Anchor Hocking TrueSeal Glass Storage got a B+ from Good Housekeeping, but Cook’s Illustrated (subscription required) does not recommend them, because the seal became noticeably looser after running through the dishwasher 50 times and leaked profusely.

The Bormioli Rocco Frigoverre Fun line (which appears to be the same as the Ziploc VersaGlass line) is made in Italy. These containers did not stay as airtight as other glass containers in Good Housekeeping’s tests.

Plastic sets

The Rubbermaid Easy Find Lid 42-Piece Set leaked both before and after running through the dishwasher so we were able to dismiss.

The Popit Little Big Box Food Plastic Container Set didn’t leak when filled with water, and the removable gasket made cleaning easy. However, this set didn’t pass our drop test: The flaps popped open, and one completely broke off.

The Rubbermaid Premier set did very well in nearly all of our tests, but it was difficult to tell when the lid was sealed properly. We also felt the container sizes were a little too small for holding leftovers.

The Emsa Clip & Close (formerly Frieling Emsa Clip & Close) containers turned bright red after being microwaved with pasta sauce in tests done by Good Housekeeping. This set performed fairly well in every test of ours except the drop test, in which the flaps opened easily.

The Snapware Airtight Plastic Food Container Set we recommended in 2015 had faulty lid flaps that were difficult to close when tested again in 2016. This set also held onto food odors and stains more than the competition.

The OXO Good Grips LockTop containers received praise from Cook’s Illustrated (subscription required) for their easy, flap-free pressed seal, but these cracked in our drop test. (One Amazon customer had a similar experience.) And they seemed less airtight, leaving our strawberries tasting fermented after 13 days.

Lock & Lock containers boast a recommendation from Cook’s Illustrated and raves from some commenters at Serious Eats and The Kitchn, but we couldn’t find them in any of the stores we visited, and only a few online retailers actually keep them in stock.

Rubbermaid Lock-its have tops that snap neatly to their nesting bottoms, so keeping mates together is easy. Though Good Housekeeping calls these containers its top choice “for packing up leftovers after dinner,” Cook’s Illustrated labels them “Not Recommended” because the seals distorted in the microwave.

Sterilite Ultra-Seal containers, which you can find at many retailers, received poor marks from both Cook’s Illustrated and Good Housekeeping for a seal that wasn’t airtight.

The Glad MatchWare color-coded lids and containers made matching pairs easy, but they leaked, stained, had left ground meat covered with freezer burn. These containers also exploded in our drop tests.

The Ziploc Starter Set Variety Pack containers nest well, but they leaked and became extremely soft when microwaved.

The Reditainer Deli Food Storage Containers are typically used in professional restaurant kitchens because they’re cheap to buy in bulk, are uniform, and store very neatly. Although these containers didn’t leak and kept freezer burn at bay, they stained easily and hung onto food odors. These containers also shattered in our drop test.


1. Please Explain: Endocrine Disruptors and Human Health, The Leonard Lopate Show, February 22, 2013

2. Betty Gold, The Best Food Storage Containers for Keeping All Your Leftovers Fresh, Good Housekeeping, October 30, 2017

3. European Food Safety Authority, No consumer health risk from bisphenol A exposure, January 21, 2015

4. Johanna R. Rochester and Ashley L. Bolden, Bisphenol S and F: A Systematic Review and Comparison of the Hormonal Activity of Bisphenol A Substitutes, Environmental Health Perspectives, July 1, 2015

5. Nancy Hopkins, senior deputy food and entertaining editor for Better Homes and Gardens, phone interview

6. Faith Durand, executive editor for The Kitchn, email interview

7. Michele Thomas, then executive editor at the International Culinary Center, email interview, January 28, 2016

8. Jane Cook, PhD, chief scientist at the Corning Museum of Glass in Corning, New York, phone interview, September 15, 2017

9. William C. LaCourse, PhD, a professor in the Glass Engineering Science department at Alfred University in Alfred, New York, phone interview, September 12, 2017

10. Heated Glass Comparison, Virtroglazings.com

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