Tea and stainless steel - stain or corrosion? How to clean?

February 3, 2020 12:35 PM

I have a stainless steel travel mug which is used exclusively for black tea. It has been very heavily used (daily for about 5 years), and the insides are permanently brown and feel pitted. But I don't know whether this is due to build-up of tea and minerals, in which case I could possibly get it off, or whether the tea has just eaten into the metal.

I'm at the point of looking to buy a new mug, but I can't find one in this shape and I'd like to give it a try to save it. I have already tried scrubbing the inside with baking soda and vinegar - and I think I was able to remove some of the stain/crud, which suggests that it is a build-up rather than that the metal itself has been corroded.

But I didn't get much off, which means that even if it is build-up, I need something stronger than baking soda. I have used cleaning tablets in the past for industrial coffee makers, and I have heard they can be used to clean very stained cups. Any specific suggestions for a very strong descaling agent that might work on 5 years worth of tea and tannins and who knows what else?

posted by jb to Home & Garden (20 answers total)

It's probably removable with a scouring pad. I drink a lot of strong black tea and my drinking objects get a heavy build up of something which comes off with vigorous scrubbing using a new scotchbrite pad (old pads aren't abrasive enough). It takes HARD pressure and hard scrubbing. I haven't found baking soda to help, nor vinegar, just elbow grease
posted by anadem at 12:46 PM on February 3, 2020 [1 favorite]

It's a build-up of tea oils, mostly. If you can put it in the dishwasher, do so, maybe a few times in a row.

You can also try hot vinegar (without baking soda).
posted by snakeling at 12:47 PM on February 3, 2020

we use either this exact brand or something similar to clean our metal water bottles and travel mugs. works really well (like they sparkle, and one time when i didnt fill my mug all the way i had to use a second tab because it bothered me that i could see the top half inch was still scaled)

I'm not a tea expert but i DID almost ruin my sister in laws (ceramic) tea pot by trying to descale it. shes a constant tea drinker and said i would have ruined her built up seasoning. this experience leads me to believe that your seeing "pitting" in the build up layer and that its all just caked on top of, not eating into, your travel mug.
posted by Exceptional_Hubris at 12:48 PM on February 3, 2020

May I suggest just using denture cleaning tabs? They work a treat on all my teapots and mugs. Considering the old friend level of tea stains you may need to do more than a round of the cleaner. Denture cleaning tabs were designed to remove these kinds of stains and also work overnight. Further, if your mug has many curves or crannies then soaking with a solution reaches where you can't.

Another one is just using plain vinegar and letting it sit as well. I find this works for mineral deposits. I clean my electric kettle with a vinegar soak. Cheap vinegar is fine and diluted 1:1 still gets the work done but this too takes a touch of time.

TL;DR soak the mug with denture cleaner or vinegar overnight.
posted by jadepearl at 12:48 PM on February 3, 2020 [7 favorites]

If you're 100% sure it's raw stainless steel (no coatings), Bar Keeper's Friend will clean it out.

Avoid using it on parts that are painted, have graphics, are polished (shouldn't matter if it's on the inside where you can't see it) etc as it's likely to scuff/mar/remove it.
posted by pullayup at 12:59 PM on February 3, 2020 [1 favorite]

You could also try a cut lemon and salt.
posted by pinochiette at 1:12 PM on February 3, 2020

OK, if it's stained from tea, the first thing to try is filling it with distilled white vinegar and leaving it for a couple of days, then washing it with detergent. Your baking soda scrubbing won't have gotten the full benefit from the vinegar, since baking soda reacts with vinegar.

Just fill it and let it sit for a while, then wash, then see what you've got.

Don't scour/scrub it more than you absolutely need to in order to avoid abrading/scratching the metal.
posted by amtho at 1:29 PM on February 3, 2020 [1 favorite]

Actually, the first thing to try is vinegar soaking it for a few hours -- that might be enough.
posted by amtho at 1:29 PM on February 3, 2020

Have you tried Dawn and warm water? Let it sit for 15 minutes before you try to clean it.
posted by vitout at 3:31 PM on February 3, 2020 [1 favorite]

I usually put a drop of bleach in a stained mug. Fill with water and let sit a while.
posted by Enid Lareg at 3:36 PM on February 3, 2020

I came in to suggest denture tabs -- I see that jadepearl beat me to it! So - seconding this recommendation.

I've taken care of coffee & tea build-up on stainless steel with denture tabs; if the build up is very heavy it may take more than one soak. I think that starting with a vinegar soak is a good first step. If that doesn't do it, I'd graduate to the denture tabs.

For "scouring," you can sometimes get good results using ice cubes. Soak the mug, then empty it. Fill a little ways with water and then some ice cubes. Put on the lid & shake it all around, then dump out. I've had some very stubborn coffee build-up in our stainless steel carafe, and using these three methods together had it looking brand new.
posted by dryad at 3:42 PM on February 3, 2020 [2 favorites]

I came in to recommend Bar Keeper's Friend, seconding pullayup.
posted by under_petticoat_rule at 3:48 PM on February 3, 2020

Do you put it in the dishwasher ever? We had a stainless tea strainer that was perfectly brown after years of hand washing (scrubbing, really). We bought a dishwasher and used Ecover dishwasher tabs and the first time we washed it it came out stainless steel colored again.
posted by oneirodynia at 4:24 PM on February 3, 2020 [1 favorite]

I cleaned my thermos just last week and can vouch for vinegar! Extended soaking time will do it.
I've also used bleach on china teacups and that works well but I haven't tried it on metal containers.
posted by storybored at 4:39 PM on February 3, 2020

Try a non-scratching abrasive such as Bon Ami, or even toothpaste.

If I knew of any legitimate copper based scrubbers left out there (Chore Boy is now only copper plated), I'd recommend using one of those.
posted by jamjam at 4:41 PM on February 3, 2020

Speaking from years working in coffee houses -- cafiza. It's designed to break down the oils in coffee and tea and it cleans like a gd dream. It says it cleans commercial espresso machines, but we used it on all of our equipment, utensils, glassware, etc. Hot water, a small scoop of this powder and a ten minute soak. Scour with a bristle brush, then rinse.
posted by kaelynski at 4:53 PM on February 3, 2020 [4 favorites]

Nthing denture tabs. They are amazing for coffee and tea stains on just about everything, plus you just drop it in and forget it. Bar Keeper's friend is also good for scouring stainless, but you have to wash it really well after to avoid residual metal taste/smell.
posted by bowtiesarecool at 5:08 PM on February 3, 2020

I have used a cleaner for brewing called PBW. The stuff is like Oxyclean on steroids. I've used it in this exact scenario and it restore it to nearly new.
posted by slogger at 8:15 AM on February 4, 2020

Response by poster: Reporting back: a 36-48 hour soak with pure white vinegar has had little to no effect.

Perhaps staining isn't the best way to describe it; it's clearly either a build-up on or corrosion into the metal, as you can feel it as much as see it. As I mentioned, I seemed to get a bit off scrubbing with baking soda (I did baking soda and vinegar, and also just a baking soda and water paste, which is very effective on other things) with lots and lots of hard scrubbing, so I was leaning towards build-up. But the vinegar hasn't dented it at all.

I guess my next step is one of the more specialized cleaners, or maybe toothpaste.
posted by jb at 12:12 PM on February 5, 2020

You can try to clean it with bleach. Take a look at this article, there are many ways to clean a teapot. I cleaned my thermos just last week and can vouch for vinegar! Extended soaking time will do it.
I've also used bleach on china teacups and that works well but I haven't tried it on metal containers.
posted by georgehanson at 3:30 AM on September 28, 2020