I use my vacuum flask to bring my lunch to work. I've been doing this almost every day for half an year or so. Now there are some sediments or stains in the bottom of the flask although I wash the flask almost always immediately after it's emptied.

How can I get rid of the stain and smell inside the flask? I even used steel wool on a stick but could't make it clean 100% and I don't want to scratch it too much inside. Because I use it for food I am not sure if bleach is a good choice to go for.


I have original Thermos made of stainless steel interior and exterior. Something like that one http://www.thermos.com/products/vacuum-insulated-10-oz-food-jar.aspx

Note that I am located in Austaralia so no cleaning products are available to me.

  • What is your thermos flask made of? Stainless, plastic, or something else?
    – derobert
    Commented Dec 18, 2012 at 16:38

5 Answers 5


I have found that a tablespoon of Oxy Clean followed by boiling water will remove even the harshest stains inside a vacuum bottle. Fill it to the brim (it will bubble and overflow, so do it in a sink), let it sit for a bit, then rinse very very well, and you will be amazed, I promise. I do this periodically to remove the coffee stains inside our steel thermos flask. [Edited for typos]

  • Looks like we don't have Oxy Clean here in Australia.
    – Radek
    Commented Dec 18, 2012 at 4:50
  • Maybe there's a local equivalent, under a different name? This page suggests a (liquid) product called Preen Oxyaction: answers.yahoo.com/question/index?qid=20071218113902AA6rLV9 -- not sure of the ratio of a liquid product to water, so you may have to experiment. I buy a powder version.
    – franko
    Commented Dec 18, 2012 at 14:46
  • 3
    "Oxy clean" is a brand name. But any peroxide-based bleach will do. (Take care not to use chlorine-based bleach).
    – rumtscho
    Commented Dec 18, 2012 at 15:08
  • @rumtscho: Great suggestion! This is a quote from Thermos website "DO NOT use bleach or cleaners containing chlorine on any parts of the product."
    – Radek
    Commented Dec 18, 2012 at 21:35
  • Re: Rumtscho's suggestion, you could try soaking it in a water/hydrogen peroxide mix.
    – daisy_ann
    Commented Dec 19, 2012 at 0:03

A combination of coarse salt and vinegar is usually very effective. The coarse salt is used as an abrasive.

  • 2
    Salt also reacts chemically with vinegar to make a stronger acid: chemistry.stackexchange.com/questions/2765/…
    – john3103
    Commented Oct 9, 2014 at 15:13
  • Likely stains are embedded in hard water build up, mineral salts. A good long soak in vinegar/NaCl should dissolve the mineral deposits. Stainless will not mind an overnight soak, and it is much easier than trying to get the stuff off with steel wool. Commented Oct 9, 2014 at 16:59

I would scrub it with baking soda.


Try a Steradent (or similar denture cleaning tablet) or two in hot/boiling water. Will froth up, so do in sink until it settles.

Steradents are available from any good local supermarket in the Oral care section. Designed for dentures so safe for food/drink containers. Great for cleaning many kitchen utilities such as electric jugs etc.


Thermoclean (available in the UK) is meant specifically for cleaning vacuum flasks.

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