How to Clean a Flask

Brielle asked, “How does one clean a flask?”

You Will Need:

• Dish detergent
• Boiling water
• Baking soda
• Vinegar or Lemon juice
• Denture cleaning tablets
• Tea
• Clean dry polishing cloth
• Lemon oil

Steps to Clean the Flask:

1. When you finish with a flask, immediately rinse it with hot water and a few drops of dish detergent.¹ Rinse and place the flask upside down to drain. Allow to totally dry before storing. Store with the lid off to prevent smells.¹
2. If the flask is a little bit dirty from juice or a liquid other than water, and carefully pour boiling water into it. Use tongs to hold the flask while you pour or prop the flask up in a dish tray while you pour to avoid getting burned. Let the hot water sit for approximately five minutes, then rinse and follow the storage guidelines mentioned above.¹
3. When you have found that you forgot to clean out your flask the last time you used it and some liquid as dried out on the inside, carefully pour boiling water into it and add a couple of tablespoons of baking soda. Swish the mixture around and let it sit for a few hours. Rinse and follow the storage guidelines mentioned above.¹
4. If you find that there is a residual smell, you can also soak the flask in a mixture of hot water and either vinegar or lemon juice.¹
5. Typically hard water and coffee are the two liquids that stain a flask’s steel inside. You can try removing the stains with a few denture cleaning tablets. Just mix with hot water and allow to sit for about eight hours.¹
6. It there is a metallic taste to the fluids in your flask, pour a strong tea into the flask and allow it to soak for a couple hours.²
7. Usually a clean, dry cotton cloth is all that is needed to polish the outside of a stainless steel flask, but if you do need a bit more help, try a dab of lemon oil. Apply the lemon oil to a clean, dry cloth and buff the outside of the flask until it shines.¹

• If you need a little more elbow grease to get out something on the inside of the flask, you can use a bottle brush.² These can be found in the kitchen accessory aisle or in the infant product aisle of most grocery stores.
• Do not use chlorine bleach or a cleanser with bleach in it on a stainless steel flask. There is a liner on the inside that is held together by a weld that the bleach can destroy.²
• Also, do not use any cleaner that has abrasives in it. And, stay away from scrub pads. These can permanently scratch the surface.²
• Usually it is safe to place stainless steel in the dishwasher, but because there are so many sizes, shapes, and styles in use today, check your manufacture’s guidelines before taking this cleaning shortcut.³

1. Clean it Fast, Clean it RIGHT by Jeff Bredenberg
2. The Cleaning Encyclopedia by Don Aslett
3. Home Comforts; The Art & Science of Keeping House by Cheryl Mendelson