Source: https://www.capra.pk/blog/how-to-clean-a-thermos-flask Care28 September 2026 ยท 2 min read # How to clean a thermos flask: tea stains, smells and the lid How to clean a stainless steel thermos or vacuum jug at home: remove brown tea stains, get rid of smells, clean the lid and seal, and what never to use. Doodh patti leaves a brown film inside any flask, and a lid that is never taken apart starts to smell. The good news is that stainless steel cleans easily with things already in a Pakistani kitchen. Here is how we clean our own CAPRA jugs and bottles. ## Everyday cleaning Rinse the flask with warm water as soon as it is empty, before the tea dries on. Once a day, wash it with warm water and a drop of washing-up liquid, using a soft bottle brush for the inside and the neck. Rinse well and leave it upside down to dry with the lid off, so no moisture is trapped inside. ## Removing brown tea stains For stains, add two tablespoons of baking soda (meetha soda) to the flask, fill it with hot water, close it and leave it for 20 minutes to an hour. Pour it out, scrub gently with the brush and rinse. For heavy stains, leave it overnight. White vinegar works too: fill the flask a quarter full with vinegar, top up with hot water and leave it for an hour before washing. Lemon juice with a little salt does the same job if you have no vinegar. ## Getting rid of smells A smell almost always comes from the lid, not the steel. Unscrew the lid, take out any removable seal or gasket, and wash each part in warm soapy water. Soak the seal in baking soda water for half an hour if it smells, then let every part dry completely before you put it back together. Store the flask with the lid off, or loosely resting on top. A flask sealed while damp is the most common cause of a sour smell. ## What never to use Do not use bleach or chlorine cleaners, which can pit stainless steel and damage seals. Do not use steel wool or scouring powder, which scratches the inside and gives stains somewhere to cling. Do not put the flask in a dishwasher or microwave, and never freeze it full of liquid. ## How often to deep clean If you drink chai from the flask every day, a baking soda clean once a week keeps it bright. Take the lid apart and wash the seal at the same time. Looked after this way, a stainless steel flask stays clean and fresh for years. ## Common questions **How do I remove tea stains from a thermos?** Fill it with hot water and two tablespoons of baking soda, close it and leave it for 20 minutes to overnight, then scrub with a soft bottle brush and rinse. **Can I wash a vacuum flask in a dishwasher?** No. Hand wash it with warm soapy water. A dishwasher can damage the seal and the outer finish. **Why does my flask smell?** Usually because the lid and its seal have not been taken apart and dried. Wash each part, soak the seal in baking soda water, and store the flask with the lid off. [The CAPRA care guide: use, clean and store](https://www.capra.pk/care-guide) ## More from the journal [All articles](https://www.capra.pk/blog) [Prices3 min ### Thermos price in Pakistan (2026): what a good vacuum flask costs What a stainless steel thermos, vacuum jug or insulated bottle costs in Pakistan in 2026, size by size, and what you get for the money at each price. Read](https://www.capra.pk/blog/thermos-price-in-pakistan) [Buying advice2 min ### How to choose a vacuum flask: size, lid and steel explained A plain guide to choosing a thermos jug or insulated bottle: which size suits your family, which lid pours best, and how to tell good stainless steel from bad. Read](https://www.capra.pk/blog/how-to-choose-a-vacuum-flask) [Guides2 min ### How long does a vacuum flask keep tea hot? Seven ways to make it last What decides how long a thermos keeps chai hot or water cold, and seven simple habits that make any vacuum flask hold its temperature for longer. Read](https://www.capra.pk/blog/how-long-does-a-vacuum-flask-keep-tea-hot) ## Order today, pay when it arrives. Cash on delivery to every city in Pakistan. We call to confirm before we send, and every flask carries a 2-year warranty. [Shop the range](https://www.capra.pk/shop) [WhatsApp 0311 0075000](https://wa.me/923110075000)