How to remove coffee stains from stainless steel thermos

Originally Published April 6, 2021

Do you have a stained stainless coffee thermos that you can’t get clean? I’ve got a great way how to clean a coffee thermos cheaply and quickly!

I love coffee and though I don’t work outside the home currently, I do use a coffee thermos for safety in case my kids knock it over. My main coffee thermos is stainless steel inside and gets stained with coffee often. I’ve tried a lot of ways to clean it but I couldn’t get the stains out, until now.

Different Approaches on How to Clean a Coffee Thermos

I had tried a lot of different ways to clean the coffee stains out of my stainless steel thermos but none worked. I had tried basic dish soap and water, but not good enough. Even letting the mixture soak for hours and then coming at it with a bottle brush didn’t work. Vinegar and baking soda seemed promising but that didn’t do it either. Each time I tried it would help a little bit but the thermos still had coffee stains.

Then I found a suggestion online which included using denture cleaner tablets to clean the thermos. Even though I’m only in my 30s, I had denture cleaner tablets on hand since I use them to clean my retainer. I figured it was worth a try since nothing else had done the job.

Below you can see the inside of my thermos. It’s worse than it looks, the coffee stain inside goes up a few inches from the bottom but that was hard to capture on camera. On the right is the outside of the thermos with the cleaning tablet package in front of it.

Cleaning a Thermos with Denture Tablets

1. Be sure you’re by a sink so you can put your thermos in it while it soaks. This is to ensure if it bubbles over it goes in the sink and not on your desk.
2. Add warm or hot water to the thermos, at least half way up.
3. Drop in the denture tablet and let it do it’s work. Keep the lid off.
4. Let the denture solution soak in your thermos for about 30 minutes.
5. After 30 minutes, use a wash cloth, or bottle brush if you have one, and scrub the inside of your thermos.
6. Dump out the solution and clean with dish detergent and water like usual.
   1. If you have particularly stubborn stains, do it all over again. Personally, the sides of the bottom 1/4 of my thermos often need more attention.
7. Admire your amazingly clean thermos for a few seconds before brewing more coffee. 🙂

In the third picture above I’m showing a tiny brush with the lid of my coffee thermos. This lid is really frustrating as it has so many tight spots it’s hard to get clean. I purchased these tiny brushes which are the only thing I’ve found to be able to clean in the crevices.

In all honesty, the first time didn’t get it as squeaky clean as I wanted so I used another denture tablet and just used enough water to cover the problem areas. After another 30 minutes and a little scrub with the bottle brush, it was looking like new!!

Steps to Keep your Thermos Clean Longer

Maybe it’s just me but I feel like my coffee starts to taste weird when a lot of sediment builds up. Here are some tips to keep your thermos stain-free longer.

• Wash your thermos daily, or multiple times a day if you can.
• Rinse out your thermos with water as soon as you finish drinking your coffee.
• Soak your thermos in dish soap and water for an extended period of time when needed.

I don’t have a particular timeline of when I use the denture cleaner for cleaning my thermos but I do buy the large box of denture cleaner so I have it on hand whenever I need it.

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