A vacuum thermos flask can be easily cleaned without much effort using these methods.
- Hang one or two teabags in the flask.
- Pour boiling water in the flask, fill up completely.
- Screw the cap on.
- Let it sit overnight.
- Pour tea out of the flask.
- Rinse flask with clear water.
- Break some eggshells into small pieces.You can grind the eggshell into a powder if you wish to.
- Put broken egg shells into the flask.
- Fill up the flask part-way with clean cold water.
- Close the cover securely and shake the flask for 30 seconds.
- Open the cover and remove the contents from the flask. If the stain is not completely gone, repeat steps 2 through 4.
Method 3 of 4: Baking soda and vinegar
- Put about 1” of vinegar and few drops of lemon into the bottom of the thermos
- add 1 tablespoon baking soda for every 2 cups that the thermos holds.
- Quickly fill the thermos with boiling water.
- It’ll foam and don’t cap, let sit, scrub and rinse.
Method 4 of 4: Ice and salt
- Fill the thermos about ¼ full of ice (smaller cubes work best) and add 2 to 3 tablespoons salt.
- and shake. The ice and salt are scrubbing away at the side walls as you shake so by twisting and turning the thermos, you’ll gradually wear away all gunk.
- Discard and rinse. This works, but it takes a fair amount of effort….. and ice.