Glass food storage containers — and the lids nobody declares

• The composition and the tempering explanation are on Anchor Hocking’s “why choose glass” page, not the TrueSeal product page. Both linked below. [2]
• Lid resin and gasket material are not stated. The lid is a food-contact part, which is why the composition is not counted as fully declared. [1]
• On testing, their FAQ answers the lead-and-cadmium question with “Yes, and also CA Prop 65 compliant.” That is the whole answer. It names an external standard, so it scores 1 — but there is no laboratory, no method and no report behind it. No warranty is published either. [4]
• 425°F ceiling — above that counts as misuse. [1]
• Their framing that soda-lime is “a modern improvement over borosilicate” is a competitive claim, not a neutral one. Their own precise wording is that tempered soda-lime has “equal to or greater thermal shock resistance than annealed borosilicate” — a tempered-versus-annealed comparison, which is not the same as tempered-versus-tempered. [2] [3]

Sources (4)

1. Anchor Hocking TrueSeal
2. Anchor Hocking, “why choose glass” — the published oxide composition
3. Anchor Hocking bakeware facts
4. Anchor Hocking FAQ — the lead, cadmium and Prop 65 answer

• “No lead added during fabrication” is carefully worded. It addresses the process, not the finished product, and no test result is offered alongside it. [1]
• Made in France, stated plainly, and manufactured “to French and European food-safety standards”. [1]
• The dishwasher, freezer and microwave guidance lives inside product images rather than in page text, which makes it easy to miss. [1]
• No oven guidance, no temperature limit and no thermal-shock warning — on soda-lime glass, which tolerates thermal shock poorly. Compare WECK below, which publishes a differential. [2]

Sources (2)

1. Le Parfait Super Jar product page
2. Le Parfait America — airtight jars with replaceable seals

• Three different oven numbers appear on one of U-Konserve’s own pages: these containers are “oven safe up to 300ºF”, the BounceBox is “oven safe up to 425ºF”, and discolouration is said to start above 450°F with a do-not-exceed of 600°F. [2]
• 300°F is a strikingly low rating for 304 steel and is almost certainly a limit imposed by the silicone lid or the assembly, not by the metal. The page does not say so. [2]
• “Naturally free from BPA, BPS, lead, and other toxins” is open-ended; the product page’s narrower “No BPA, BPS, phthalates, or lead” is the defensible version of the same claim. [1] [2]
• No warranty published anywhere we could find. Manufacture is stated as China, in BSCI-certified facilities. [1] [2]

Sources (2)

1. U-Konserve Rectangle Container product page
2. U-Konserve Product Information — steel grade and the three oven figures

• “FDA approved silicone” appears on their site but attached to a different product line, not this container. [1]
• The lid is not dishwasher or oven safe, which undercuts the point of a steel container somewhat. [1]
• No warranty published. [1]
• Their site redirects to an unencrypted connection, which is a poor look for a 2026 storefront. [1]

Sources (1)

1. Onyx 18cm airtight container

• “BPA Free” on a steel and silicone insulated canister — never in question, and the claim does no work. [1]
• No silicone standard for the cap gasket, and the lid’s plastic parts are not itemised, so the food-contact polymer inventory is incomplete. [1] [3]
• No microwave, oven or freezer guidance published at all for this product — a gap made conspicuous by Klean Kanteen’s own Rise Food Box, which carries explicit 350°F and 1000W limits. [1]
• For context on why the vacuum seal matters: the CPSC recalled several brands of children’s stainless drinkware in 2023 over lead in the solder sealing the base. [4]

Sources (4)

1. Klean Kanteen 16 oz TKCanister insulated food container
2. Klean Kanteen FAQ — 18/8 definition and the silica/glass vacuum plugs
3. Klean Kanteen warranty
4. CPSC — Green Sprouts recall over lead in the base solder, 2023

• Libbey’s own dedicated storage line does not do this. The “Serve It” 8-piece glass storage set and the small bowls with lids declare only “glass”. Same maker, same shop, one page declares and the others do not. [2] [3] [4]
• Declared oven safe with no temperature ceiling and no thermal-shock figure, on soda-lime glass — whose weak point is precisely thermal shock. The Serve It page adds “do not transfer containers directly from freezer to oven”; this page omits that caution entirely, so two Libbey pages give different safety information about the same glass. [1] [3]
• No product warranty at all — only a 30-day window to report a problem with an order, which is a retail term rather than a guarantee. [5]
• The lid resin is never named, and the URL slug reads “storage-basics” while the title reads “Baker’s Basics”. Merchandised as storage, titled as bakeware. [1]

Sources (5)

1. Libbey Baker's Basics 4-piece glass bowl set with lids
2. Libbey storage collection
3. Libbey Serve It glass storage set — glass type absent, freezer-to-oven caution present
4. Libbey small glass bowls with lids — glass type absent
5. Libbey returns and replacements — the 30-day window

• The product page drops the word “platinum” and says only “premium food-grade silicone”. The material distinction survives only on the FAQ. [1] [2]
• “Food-grade… one of the highest quality tiers” is marketing. There is no tiered food-grade silicone rating scheme, and no agency issues a food-grade certificate. [2]
• The two pages word the same claim differently — “and phthalates” against “or other phthalates”. The second phrasing implies BPA and BPS are phthalates, which they are not. [1] [2]
• Credit: a 425°F oven rating with an explicit exclusion for broilers, open flames and sharp objects is more specific than anything else in this category. [1]

Sources (2)

1. Stasher Gallon Bag product page
2. Stasher materials and FAQ page — the platinum cure

• Natural rubber rings are the only sealing part, they are consumable and sold separately, and natural rubber is a latex-allergy consideration the pages never raise. [1]
• Freezer safety is conditional on buying a separate plastic Keep Fresh Cover, and only for three of the jar shapes. Wood lids are refrigerator-only; cork is neither. [1]
• No “free of” claim of any kind. On a jar with no coating and no plastic in the food zone that is defensible restraint — but the glass type still goes undeclared. [1]
• Company origin is given as Oflingen, Germany. The current country of manufacture for the jars is not stated as such. [2]

Sources (2)

1. WECK FAQ — the 122°F differential, rubber rings, freezer conditions
2. WECK About page

• “Heat resistant glass” is a performance adjective standing in for a composition. It is declared oven-safe with no temperature ceiling and no thermal-shock warning. [1]
• No “free of” claims at all, and no product warranty — only a 365-day returns policy, which is a retail term rather than a guarantee about the product. [1]
• Credit: the lid and seal disclosure is more specific than Rubbermaid’s, whose lid is given only as the trade name “StainShield”. [2]

Sources (2)

1. IKEA 365+ food container with lid, rectangular glass 34 oz
2. IKEA 365+ food storage range

• Glasslock sells both a standard line and this “Oven Safe” line, and the site never explains the material difference between them. A buyer cannot tell what the premium buys. [1] [2]
• No warranty, no oven instructions and no thermal-shock guidance on the product page, the category page or the brand page. [1] [2]
• “Do not contain harmful environmental hormones” is a claim well beyond BPA, offered with no testing, no standard and no reporting limit. [2]
• Credit: country of manufacture is stated plainly — “all of our Glasslock products are made and assembled in S. Korea”. [2]

Sources (2)

1. Glasslock 18pc Oven Safe Box Set
2. Glasslock — “What is Glasslock?” brand page, with the glass recipe

• The warranty covers breakage “from oven heat” for two years. Thermal-shock breakage from a cold counter — which Pyrex’s own safety page warns about at length — is not what the warranty promises to replace. [2]
• A 450°F figure exists on the safety page but is scoped to “bakeware”, leaving this storage vessel’s limit undeclared. [2]
• Credit: the safety page is unusually thorough on thermal shock — do not add liquid to hot glassware, do not put hot glass on a countertop, a metal surface or in the sink. [2]
• Pyrex states it tests for lead and cadmium at third-party laboratories. No laboratory is named and no certificate is published. [3]

Sources (3)

1. Snapware Total Solution Pyrex 10-piece set
2. Pyrex product warranties, safety and usage
3. Pyrex FAQ — “we produce both soda-lime and borosilicate glass”

• The FAQ mis-converts a temperature difference as if it were an absolute temperature: “resistant to thermal shocks ΔT from 100°C / 212°F to 160°C / 320°F”. A ΔT of 100°C is 180°F, not 212°F. The published shock ratings overstate in Fahrenheit. [2]
• Two of their own pages disagree on origin: the product page says “all components are made in Italy”, while the FAQ says “most of our glassware is made at our factory in Fidenza and Parma… some of our items are manufactured for us by skilled artisans in glassworks in Spain, Germany, Turkey and China”. [1] [2]
• Credit: the FAQ makes a broad and specific material claim — “all of our glass products past and present are lead, cadmium, BPA, arsenic and heavy metal free”. [2]
• No warranty published. [1]

Sources (2)

1. Bormioli Rocco Frigoverre 4.7-cup rectangle, set of 8
2. Bormioli Rocco FAQ — material claims, the ΔT conversion, the origin list

• That steel rim is a real hazard disclosed only in the warranty clause: microwaving voids the warranty if the rim is exposed. A buyer reading the product page alone would not see it. [1] [2]
• Oven safe to 415°F — but not the lids. A two-part limit that is easy to get wrong. [1] [2]
• A mixed-material set under one SKU: silicone, stoneware, plastic lids and steel, made in two countries. The stoneware is made in the USA; the silicone in China. [2]
• Credit: the plastic lids are declared “free of BPA, lead, PVC, and phthalates” separately from the silicone claims, rather than blanketing everything under one sentence. [1]

Sources (2)

1. Souper Cubes Complete 29-piece set
2. Souper Cubes FAQ — cure type, FDA vs LFGB, the steel rim, warranty

• Two Ball product pages disagree: the Wide Mouth page states “Freezer Safe: Yes” and the Regular Mouth quart page states “Freezer Safe: No”, with no explanation. The real reason is the shouldered neck on regular-mouth jars, and Ball never says it. [1] [2]
• “BPA-free” is the only chemical claim, and the lid’s sealing compound — the part that actually touches food, and where BPA historically lived — is never identified. [1] [3]
• Lids are single-use for canning and bands are reusable. Stated clearly, which matters for a consumable part. [3]
• No warranty published anywhere we could find. [1]

Sources (3)

1. Ball Mason Jars & Lids, Wide Mouth 12-pack
2. Ball Mason Jars & Lids, Regular Mouth — the contradicting freezer line
3. Ball wide mouth jar lids and bands, 12pk

• The only caution offered is “do not place container on wet or cold surface” — an implicit admission that thermal shock is the real failure mode, while declining to quantify it. [1]
• A “Limited Lifetime Warranty” on “defects in materials or workmanship”, for a glass container, with no stated position on breakage — the one failure a glass-container buyer actually cares about. [1]
• “BPA Free” is the only chemical claim. No lead or cadmium statement, where Duralex, Libbey and Bormioli all make one; no lid resin, no silicone standard, no country of manufacture. [1] [2]
• Ello’s FAQ page would not load for us, so glass type, lid resin and origin stay unverified from the maker rather than being filled from a retailer. [3]

Sources (3)

1. Ello Duraglass 5 Cup Food Storage Container
2. Ello Duraglass 2 Cup Round — same undeclared glass across the line
3. Ello FAQ — would not load

• One brand name, two different materials: “Brilliance” covers both this glass line and a Tritan plastic line, so listings and reviews routinely mix them up. [1] [2]
• Rubbermaid’s own help-centre articles on Brilliance materials and care would not render for us, so the material detail is effectively unreachable on their site. [2]
• The limited warranty and satisfaction guarantee are referenced by link only; no terms appear on the product page. [1]

Sources (2)

1. Rubbermaid Brilliance Glass Food Storage Container Set
2. Rubbermaid Brilliance category page — Tritan and glass lines under one name

• Credit where it is due: Duralex is the only maker in this category publishing both an operating range — “−4°F to 266°F” — and a delta-T shock limit at all. Getting the arithmetic wrong is a smaller failing than not publishing a number. [3]
• The glass is described only as “tempered”. Tempered soda-lime and borosilicate behave very differently under thermal shock and break differently, and Duralex never says which it is even while quantifying shock limits. [1] [3]
• The lid polymer is never named — and the lid is the part sealing against food in the fridge. [1]
• Listed “Final Sale”, non-returnable and non-refundable, with no published warranty. Made in France at their own factory in La Chapelle-Saint-Mesmin, which is stated plainly. [1]

Sources (3)

1. Duralex Freshbox square bowl with lid
2. Duralex Freshbox round bowl with lid — lid material also absent
3. Duralex — benefits of Duralex glassware, where all three figures appear together

• The summary bullet says the containers are “microwave, oven, refrigerator, freezer & dishwasher safe” without qualification. The detail then says “top-rack” dishwasher and “Preheated Oven Safe Up to 450°F”. Two meaningful restrictions dropped from the headline. [1]
• No gasket or seal material is given, despite the “Airtight, leak-proof” claim, which implies one. [1]
• Country of manufacture not published. No warranty. No third-party testing. [1]
• Brand naming is muddled on the page itself: the title says “Snapware Pyrex” and the spec table says “Brand: Pyrex”. Pyrex Europe is borosilicate and Pyrex US is tempered soda-lime — two glasses, one name. [1]

Sources (1)

1. Costco — Snapware Pyrex 18-Piece Glass Food Storage Set

• They do assert testing, and we had this at zero before we looked properly. The FAQ says they “routinely test our Pyrex products for harmful lead and cadmium content at internationally recognized, third-party laboratories”. No laboratory is named, no result is published and no frequency is given, so it scores 1 — but it is an explicit third-party testing claim and we were wrong to record nothing. [2]
• This matters practically, not just on principle: soda-lime handles thermal shock worse than borosilicate, which is exactly why Pyrex warns never to put hot glass on a cold or wet surface. The composition is the reason for the warning. [2]
• No stovetop, broiler, toaster oven or grill. Fully preheated conventional or convection oven only. [1]
• January 2023: the FTC announced a proposed consent order requiring Pyrex’s manufacturer, Instant Brands, to pay $129,416 for advertising Chinese-made measuring cups as “Made in USA”. Over 110,000 units were sold with that claim; the order was finalised in March 2023 and refunds went out in October 2024. [4]
• Instant Brands filed for Chapter 11 in mid-2023, so treat any warranty as worth checking before you rely on it.

Sources (4)

1. Pyrex Simply Store 4-piece round set
2. Pyrex FAQ — discusses both glass types without stating which is used
3. Corning Museum of Glass on Pyrex glass composition
4. FTC press release, Instant Brands “Made in USA” order, January 2023

• Two Caraway pages describe the same material two different ways — “ceramic-coated glass” and “ultra-pure, high-resistance glass”. Neither is a glass type; “ultra-pure” and “high-resistance” are not glass classifications. [1] [2]
• The airtight line claims to be free of “microplastics” on a container with a plastic lid and a silicone gasket. As stated, that claim is not measurable. [2]
• In August 2025 the NAD found Caraway’s “Free of PFAS” and “non-toxic” claims supported, while recommending it discontinue comparative claims including “Non-Toxic Swaps. Ditch the toxins and cook cleaner with Caraway!” and claims about rising “Teflon flu” cases. Credit the first half as readily as the second. [4]
• Caraway publishes heavy-metal testing — “20+ heavy metals tested, including lead and cadmium — all clear” — which is more than any other storage brand here offers. [3]

Sources (4)

1. Caraway Food Storage Set
2. Caraway Glass Airtight Container Set — the second description of the glass
3. Caraway — No Forever Chemicals
4. BBB National Programs — NAD decision on Caraway, August 2025

• The lifetime warranty openly excludes gaskets, accessories and jars — the gasket being the part that wears out. Honest, and worth knowing before you buy. [1]
• Fully US-made and specific about it: “Erie, PA USA. Our Mason jar lids are made start to finish from design, manufacture and fulfillment”. [1]
• It is a lid rather than a container. Scored here because it determines what a mason jar actually is in use, and because the disclosure contrast with OXO on this page is instructive. [1]

Sources (1)

1. reCAP Mason Jars FAQ — resin, gasket, warranty and use limits

• No resin identification code appears anywhere on Rubbermaid’s pages, and their help-centre articles on Brilliance materials would not render for us. [1] [2]
• The one-year limited warranty sits behind a linked PDF. The only term actually written into the page is a 120-day satisfaction guarantee, limited to original US purchasers from authorised sellers. [1]
• No Prop 65 or California disclosure appears on the page. [1]

Sources (2)

1. Rubbermaid Brilliance 10-Piece Set
2. Rubbermaid Brilliance category page

• No resin code, no polypropylene, nothing. “BPA-free” is a negative claim standing in for a positive identification, and it says nothing about BPS, BPF or phthalates. [1]
• The integrated spoon and fork are food-contact items with no stated material. [1]
• “Microwave and freezer” safe and “top-rack dishwasher safe” are claimed for an unnamed polymer. Microwave behaviour is entirely polymer-dependent. [1]
• “Translucent lid” — material not published. No country of manufacture. No warranty. [1]

Sources (1)

1. Walmart — Mainstays Food Storage Container Rectangle 42oz

• We are deliberately not filling this gap from a distributor listing. Material facts on this site come from the maker, and OXO publishes none, so it stays UNVERIFIED. [1]
• Only dishwasher guidance is given. There is no statement about whether these are microwave or freezer safe. [1]
• Several OXO product URLs returned 404 for us and the “Better Guarantee” page would not render its terms. OXO’s site was the least readable of any manufacturer in this category. [1] [2]

Sources (2)

1. OXO POP Container Big Square Short 2.8 qt
2. OXO POP container range