Is it plausible that my vacuum insulated mug stopped insulating?
August 20, 2019 2:17 PM   Subscribe

It seems to me that my 2 year old daily-use stainless steel double wall tumbler is not keeping water as cold as it once did. Is it likely the seal on this could have failed, or is my perspective being skewed by hot weather?

It does have a pin-sized manufactured "hole" in the center of the bottom, but it's not clear if it's an actual opening or just an indentation, and it's always been there. I'm just wondering if it's even possible for something like this to... de-vacuum(?) and if there's any way to test if that's what happened.

(Possibly irrelevant details: Corkcicle brand, always hand washed, rarely used for travel, no visible damage. Gladly receiving suggestions for longer lasting similar products in addition to answers.)
posted by gennessee to Shopping (7 answers total) 2 users marked this as a favorite
I tend to get 2-3 years out of stainless steel double wall thermos-style cups and bottles -- after that they don't keep the beverages AS cold for AS long. I usually cram my bottles full of ice and then jam the top on and I have a theory that this make micro-dents on the inside which weakens the thermal ... ness but that could be complete horseshit. Regardless, what you are describing sounds normal to me.
posted by kate blank at 2:43 PM on August 20, 2019

Lab dewars, which are basically large and heavy-duty versions of the same thing, go bad surprisingly often. Metal welds flex and fail and air gets into the bit that's supposed to be vacuum. The hole can be so small that you literally can't see it with the best optical microscope in the world and it will still eventually spoil your vacuum. (If I could get back the hours I've spent smearing gunk onto perfectly good-looking welded surfaces in order to see if it fixes a leak, I'd live a lot longer. ) But, I'm having a hard time thinking of a way to test it that won't cost way more in time and money than replacing the thing.

Getting a second model of the same kind and timing how long it takes for an ice cube in water to melt, or for a submerged thermometer to change, when they're sitting side by side isn't a bad option. Either you have two good thermoses, one of which can be given away to a friend, or you know the old one has gone bad and now you have a good one. Or, I guess, that you'd somehow managed to buy a second bad thermos. (But, it does mean giving money to a company that made a thermos that has disappointed you.)

Seeing if your qualitative impression is the same if you leave it for a few hours in an air-conditioned environment instead is easier, and arguably what actually matters.

One could come up with way more complicated schemes, like leaving the whole thing in vacuum for a while, then filling the vacuum chamber with helium for a while, then putting the object in a new or purged vacuum chamber connected to a helium leak checker. . . but, unless you've got a friend who happens to work in a lab with vacuum equipment and leak checkers, that's probably not a realistic option. Coating the thing with soapy water or similar, putting it in a vacuum chamber with a window, and looking for bubbles while pumping out the chamber might also work. . . if you have access to a vacuum chamber with windows. My guess is this will take more effort than getting a new thermos. But, it could be a lot of fun.
posted by eotvos at 3:23 PM on August 20, 2019 [7 favorites]

Yes. Tiny micro fractures etc. This is why I don’t buy high end double walled steel mugs. They all degrade.

I am very happy with my vacuum sealed double wall steel cup from Rubbermaid. It cost $10, only minor loss of insulating over 3 yrs. It will likely degrade too much in 5-6 yrs total but so will those hipster brands that cost $50.
posted by SaltySalticid at 3:29 PM on August 20, 2019

Chill it in a refrigerator, then immerse in a sink full of hot water and see whether it blows bubbles.
posted by jon1270 at 3:29 PM on August 20, 2019 [3 favorites]

Me, I have an infrared thermometer for cooking, which is a super fun toy to use for this kind of experiment.
posted by desuetude at 9:18 PM on August 20, 2019

Agree xN that they do go bad. Generally the air does insulate, but not as well as the vacuum it filled.

I suspect that the dishwasher (machine) reduces the lifespan but that's my speculation.
posted by jclarkin at 9:10 AM on August 21, 2019 [1 favorite]

The dishwasher definitely reduces lifespan, since it introduces extreme temperature changes while potentially banging your mug against other dishes—which cause the walls to flex and introduces the micro cracks described above.
It’s a thing, anyway, they don’t last forever. 3-4 years max in my experience using them for very hot liquids, even exclusively hand washing. What sucks is how hard it can be after that amount of time to find the exact same one made to the same quality standards, but that’s a different Ask.
posted by zinful at 9:51 AM on August 21, 2019

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