Corkcicle · Insulated Travel Mugs
Corkcicle Sierra Tumbler
Lower concern. Stainless steel insulated tumbler with no water-resistant treatment.
Corkcicle Sierra Tumblers use stainless steel construction without reported water-repellent coating coatings or special surface treatments. No public PFAS disclosures, but bare metal design carries lower inherent risk.
Shop Corkcicle on Amazon →Material
Stainless steel exterior, vacuum-insulated core, uncoated interior
Brand disclosure
Brand is silent on PFAS
Lab data
No public lab test
Why this grade
Safe base material
Made from a material with no inherent PFAS use (ceramic, mineral, or natural fiber).
Category baseline
other is a category where PFAS exposure is more common.
No PFAS disclosure
No public statement about PFAS in this product.
The full breakdown
What it's made of and why it matters
The Sierra Tumbler uses 18/8 stainless steel for the exterior and vacuum-insulated walls, with an uncoated interior that contacts beverages. Stainless steel does not leach significant metals under normal use because the chromium and nickel form a passive oxide layer that resists corrosion. The uncoated interior eliminates risk from polymer coatings, enamels, or ceramic glazes that might degrade or release contaminants. Vacuum insulation (air gap between walls) is inert and poses no chemical leaching concern.
The brand's record and disclosure
Corkcicle has not published detailed material safety data sheets or third-party certifications for the Sierra Tumbler. The brand maintains no prominent public stance on PFAS or chemical disclosure beyond product descriptions. No recalls or reported safety incidents specific to this tumbler model appear in public records. The company markets durability and insulation performance rather than emphasizing chemical safety testing.
How it compares in its category
Stainless steel tumblers are among the safest insulated drinkware options because they avoid plastic linings, polymer coatings prone to breakdown, and ceramic glazes that may contain lead. Most competitors in this price range use either stainless steel (similar safety profile) or double-wall plastic with potential BPA or microplastic concerns when heated. The uncoated interior is a design strength compared to enameled or silicone-lined variants that require ongoing monitoring for coating degradation.
If you buy it
Hand wash or use the dishwasher on standard cycles; avoid abrasive scrubbers that could micro-scratch the interior. Do not fill with boiling liquid and immediately seal the lid, as pressure buildup can damage the vacuum seal. Inspect the seal gasket annually for wear or discoloration; replace if it hardens or shows mold growth. The stainless steel interior will not degrade from acidic beverages (lemon water, coffee) or alcohol over typical use life.
Beyond PFAS: other things we checked
Established hazard classes for this product type, assessed from public information. These never change the PFAS grade; a Likely flag caps the Verdict at “Buy with care.”
Metal leaching (nickel/chromium)
18/8 stainless steel is resistant to corrosion under normal beverage conditions. Nickel migration is not documented for food-contact stainless steel tumblers and occurs only under extreme conditions (high salt, high acid, high temperature). No recalls or complaints on record for this product.
Coating degradation and particle shedding
The uncoated interior eliminates this risk entirely. Products with internal enamel, epoxy, or silicone linings face degradation over time; this design avoids that failure mode.
Gasket and seal off-gassing
Lid gaskets and seals are typically silicone or rubber compounds that may emit trace volatile organic compounds or off-odors when new. Soaking the assembled lid in warm water before first use, or airing out the tumbler, reduces this issue. Material composition of the lid gasket is not disclosed by Corkcicle.
Bacterial growth in moisture-trapped seals
If the tumbler is not fully dried after washing, moisture trapped in the vacuum-seal channel or lid gasket can support mold or bacterial biofilm. This is a maintenance issue rather than a material hazard and is common to all sealed tumblers.
Vacuum seal failure over time
The vacuum seal will degrade gradually with normal use and thermal cycling. Once compromised, the tumbler loses insulation but poses no chemical safety risk. Typical lifespan before noticeable seal loss is 2-5 years depending on use frequency.
What we don’t know
This grade is a model-based estimate from public materials, coatings, and brand disclosure at 72% confidence. It is not a lab result.
No independent PFAS lab test is on record for this exact product. A lab test could move the score in either direction.
The brand has not made a specific, verifiable PFAS-free statement, so part of this score reflects that missing disclosure rather than a confirmed material.
Formulations and coatings change between production runs. Always check the current label before buying.
Safer alternatives in Insulated Travel Mugs
Corkcicle
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Thermos
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How we score: every product runs through the same public 0–100 rubric based on materials, coatings, brand disclosure, lab findings, and recalls. See the full methodology → Spotted a mistake? Report an error.