I have a stainless steel thermos and had always cleaned it with Crystal dish soap and had no problem. I was always using tea, however this time I used liquid dish soap. The man used coffee with the cream in it and the coffee came out tasting sour. What happened?
I wanted to be the third to say thanks for the tip on hydrogen peroxide and baking soda. I cleaned both a thermos and a baking pan (cookie sheet) that had Thanksgiving sweet potatoes residue stuck on it -- I didn't want to scrape off the non-stick on the pan, and the mixture worked great.
Do mix the hydrogen peroxide and baking soda in a thermos or glass or some other container so you can shake it and mix everything before pouring in on the baking pan. Otherwise clumps of baking soda might block the solution from cleaning parts of the pan.
Back to the thermos cleaning: I also experimented with how much hydrogen peroxide is needed. I found that about 1"+ of hydrogen peroxide, and then regular tap water combined with about 1/5 box of baking soda set over night would clean a moderately coffee-stained thermos just fine. I did what others suggested, and put the lid on and shake it first, and then remove the lid. I let the thermos sit overnight, and dumped the floaters and any undisolved baking soda in the toilet. It might not have clogged the sink, but I didn't want to take a chance.
Thanks again to those who gave this initial tip!
Went online this morning to ask if it was safe to clean a stainless steel thermos using bleach. What I got was suggestions to use hydrogen peroxide mixed with baking soda and water or, dishwasher detergent (Cascade) and boiling water. I chose the "Cascade" method. This worked wonderfully; cleaned my coffee blackened, large thermos to a like new finish in 15 minutes with just two rounded tablespoons of detergent. Thank you David K., JMRoss, Susan from ThriftyFun, and others who suggested this method. Thank you also, Sandy, for letting me know bleach was a bad idea, that it would damage the seal/weld.
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Coffee stains in stainless steel thermos. How can they be removed?