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TOMMMMMM said

Keeping tea in a stainless steel thermos, is it OK and how long?

So I am a college student, and would prefer to be able to drink tea throughout the day, but must make it before I leave for school which is typically at 9AM. Let me first describe how I make my Black tea in order to figure out whats causing the funny taste:

-boil water in my plastic hotpot
-put 5 tsp of tea into my stainless steel carafe
-pour boiling water over the loose tea
-steep for 4 mins and then strain/pour directly into my 34 oz Nissan vacuum flask

I will usually make it around midnight or sometimes at 7am. Anyways, I then pour the tea into my stainless steel travel mug while I’m at school. Needless to say, the tea taste horrible (almost undrinkable) and smells kind of funny too. So I’m trying to figure out what is causing the terrible taste and smell.

Is it:

-the stainless steel carafe causing the taste (should I use ceramic instead)?
-the stainless steel vacuum flask causing the taste as the boiling tea is sitting in it for sometimes 8-12 hours (not really sure what else to use)
-the stainless steel travel mug (though I doubt this as the tea smells funky directly from the vacuum flash)
-Or is it simply that you cannot keep tea for as long as I am 8-12 hours and expect it to taste and smell good

I’m in the process or running some control tests so that I can pinpoint whats causing this, but I am suspecting its simply keeping the tea too long. Any ideas? Thanks!

27 Replies

I would try the tea fresh from the carafe. If it’s taste horrible already, then it could be the tea, the water, the carafe, or the way you make your tea. If your tea is fine from the carafe, then work down your list to find the culprit.

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TOMMMMMM said

I tried this and it tasted very similar to the tea steeped in my mug. I’m beginning to think it’s a combination of boiling hot tea left in the vacuum flask for a long time. Tonight I made some tea in a large glass measuring cup and then let it cool for 5 mins. It was hot but not boiling and rather drinkable. I put it in the flask and will report on it’s taste tomorrow.

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Angrboda said

I can’t imagine it’s caused by the vacuum flask itself. After all that thing was made for this purpose, isn’t it? At work, we make tea in a similar way and have it for the entire workday, so that can get 7 hours old as well towards the end of the day. Cools a bit, but doesn’t otherwise change flavour or smell.

What else have you had in it though?

Does the carafe itself smell bad? Does it need cleaning? (What have you cleaned it with? Any risk of residue?)

Is there any difference between when you make it in the morning as opposed to the night before?

TOMMMMMM said

Havent had anything else in it and there is no difference between morning and night. Usually just clean both with really hot water and neither the carafe or flask really have a smell. I’ll see if it still tastes/smells funny tomorrow. Then I’ll know it’s the flask. Stay tuned.

Angrboda said

Some teas also continue to naturally develop after the leaves have been removed. Maybe yours does that.

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TOMMMMMM said

So I made my tea around midnight last night and tried it this morning around 9 am. It tasted a bit better than the last time when I put almost boiling hot tea in it, but it still smells the same. It’s a really gross smell, which smells something like Spaghetti-O’s. The only connection I can make is both my tea and Spaghetti-O’s are stored in metal containers. I will store my tea in glass out on the counter next time to see how it tastes in the morning. Maybe it’s the tea?

Uniquity said

Have you tried an intense cleaning of all the items you’re using in the process? Buildup of tannins, etc could make it pretty nasty.

EDIT: I see that you wash it with water, but I mean an intense cleaning. Baking soda and vinegar or whatever your method may be to get it back to “neutral”.

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TOMMMMMM said

I have used dish soap and hot water and shook it vigorously. I’ll try baking soda and vinegar and see if that fixes it. Just mix them together?

Uniquity said

Pretty much – Though you’ll still want to scrub it with some sort of bottle brush or something to get the gunk off. Warning, it will be fizzy! : )

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I use several steel vacuum tumblers and something to check is the seal on the top lid, usually has a plastic ring of some sort on those things, and you literally have to scrub it in between uses sometimes if you let the tea sit in the thermos for a long period of time.
In addition to rinsing with natural cleaners like vinegar and/or baking soda, you have to be sure that you’re drying things thoroughly as well, or all the rinsing in the world won’t solve the problem. Each night I pop open the seal and run hot water through, but I also take a paper towel and wipe the plastic seal rings – there’s usually dust/coloring that rubs off even after the rinse, so if I weren’t being diligent with the drying, it would get funky very fast.

TOMMMMMM said

Bingo! I just noticed that the rubber o-ring on the thermos top is removable, and upon removing, revealed that awful smell. I threw both of them in the dishwasher so hopefully that takes care of that smell. If not, do I use the vinegar/baking soda soak on them? Also, the cap unfortunately floats.

Angrboda said

The top of my travel cup floats too, but when I give it a proper clean involving the baking powder treatment, I usually just put it in a plastic container and use a fork or similar to hold it down with, so that it’s submerged.

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TOMMMMMM said

Well I ran both through the dish washer, the plastic cap doesn’t smell, but the grey rubber o-ring still does. Can you soak rubber in vinegar?

I wouldn’t imagine the vinegar being a problem if you soak the ring for a few minutes.

TOMMMMMM said

I did try a few minutes and it didn’t seem to work, so I thought that maybe soaking it for a few hours would work (but don’t know if it will make it smell like vinegar).

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teatiemz said

Try Klean Kanteen insulated water bottles! They’re good for hot and cold water, and they’re entirely stainless steel- no annoying rubber rings. I’ve had mine for two years, and never any problems- I’ve put both hot tea and water in it (although you should refrain from putting sugar/milk/anything else in it, which makes for funky smells :/)

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season said

Same smell for me. I got a Thermos brand stainless steel vacuum bottle 1L with black cap n white rubber gasket. The smell definitely comes from cap in contact with boiling water
Any probable fix to this issue? When pouring boiling water to CUP (inner is plastic / outer is stainless) smell is intensified. How do we clean plastic parts? Factory defect?

TOMMMMMM said

I don’t actually drink out of the cup, I just use the thermos to keep my tea warm while I’m at work. I find that taking off the gray o-ring and cleaning it after a few uses controls the smell. I also put boiling water and couple tsp of baking soda in the thermos and let it sit overnight (probably do this after every 7-10 uses). Just make sure that as soon as your done with the tea in your thermos, you rinse it out. I actually rinse it out and fill it to the top with hot water so that it doesn’t air dry out inside (which can cause a smell to form). No more issues so far.

season said

Thx for the feedback. I’ve also contacted thermos’ customer care about this problem. Let’s see what happens :)

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pappillon said

i came across this site while searching for information on my vaccum flask. I like stainless steel so of course my flasks, all four are from stainless steel. I noticed varying levels of odour when i open a the caps but just thought it was the steel reacting with the hot liquid.

Just yesterday i accidentally dropped one of my flask and the bottom came off. What i believed is the heating element or what keeps the heat, is covered with a hard red resin like material and it smells horrible.

I do believe this is what is causing the odour in my flask. Thr hotter the liquid the stronger the odour. This was quite frightening as i dont know what this resin like thing is or if it dangerous to my health.

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