Cleaning Your Thermos

I am not sure why I shined a light into the old stainless steel thermos after a recent hunt, but I did. To put it bluntly, it was beyond gross! The thermos has emotional attachment to me, as it belonged to my Dad and is quite old. It became my charge to get it clean. Soaking with baking soda did some good. Scrubbing with a brush also made some progress, but not enough for my liking. I finally decided to try some denture cleaning tablets. I figured if they were good enough for Grandpa’s tobacco stained false teeth why not a thermos?

Filling the thermos nearly to the brim with warm water, I then dropped in four tablets, put the stopper in and gave it a shake. Word to the wise: Don’t put the thermos stopper back in or shake it like I did. A short time after I did that I heard a loud “POP” immediately followed by a “WHACK” as the stopper hit the ceiling. The gasses from the tablets built up enough pressure to create a stopper projectile.

After letting the bubbling action of the tablets work for about four hours, I dumped the contents of the thermos into the sink. What came out was amazing (and gross). At one point I was expecting to see Jimmy Hoffa’s body come pouring out. After several rinses with cold water the interior was clean and shiny–good as new. I suspect this would also work for that coffee-stained favorite cup as well.

Editor’s Note: Please use caution and for goodness sake, don’t cap or shake the thermos! Rinse all items well and follow the directions and cautions on the package.


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  1. Mark Viehweg June 13, 2018 at 8:28 am - Reply

    If this information about cleaning the thermos came from Mike, it has to be good!

  2. Marty June 13, 2018 at 8:54 am - Reply

    You want to see really gross, unscrew the base and take the inner flask out. Careful, older Thermos models used glass for the inner flask.

  3. Fred June 13, 2018 at 9:19 am - Reply

    There is also a product called dip it made just for doing this find it at grocery store in coffee section.

  4. Ralph June 13, 2018 at 9:46 am - Reply

    Coffee won’t never taste as good outta that thermos… :-)))

  5. Kees van Weel June 14, 2018 at 7:02 pm - Reply

    You can also use 4 tablespoons of baking soda, fill with water and let stand.

    Do NOT use bleach! It will eat away the seal of the inner flask. It will lose the vacuum and no longer keep stuff hot or cold. Don’t ask me how I found this out! I believe it will also void the warranty.

  6. Robert Moors June 17, 2018 at 7:28 pm - Reply

    Use about 1 tbs chlorine bleach in a thermos of warm water. Do not cap or fill completely full…just to the top. Let stand for about 30 minutes, dump and wash with soapy water until all is rinsed away.

  7. robert schweppenhauser June 20, 2018 at 8:38 am - Reply


  8. Larry Cleland June 22, 2018 at 8:00 am - Reply

    There won’t be no problem with taste out of that thermos. I wear dentures, use the cleaning tablets every day, wash and scrub dentures the next morning and have no after taste From the denture tablets.

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