A thermos flask that smells musty or tastes metallic almost always comes down to how it's cleaned, not how it's made. The good news: proper care takes two minutes.
Hand wash, every time
Warm water, a squeeze of washing-up liquid, and a bottle brush that actually reaches the base is all you need. On Thermoscup, the wide-mouth opening is designed specifically so a standard bottle brush fits all the way in - narrow-neck flasks are much harder to clean properly, which is often where the musty smell comes from.
Skip the dishwasher
Dishwasher heat and detergent can degrade the seals over time, and on a smart flask, it can shorten the life of the LED display. It's a small extra step to hand wash, but it protects both the insulation and the electronics.
Always dry with the lid off
This is the step people skip. A damp flask left sealed overnight is exactly how odours and mildew set in. Leave the lid off and let it air dry fully before you put it away.
Don't forget the tea separator
If your flask has a removable infuser basket, like Thermoscup's 304 stainless steel tea separator, lift it out and rinse it separately - loose tea leaves and fruit pulp left sitting in the mesh is the fastest way to pick up stale flavours in your next brew.
A vinegar rinse for stubborn staleness
If a smell has already set in, a mix of warm water and a spoonful of white vinegar left to sit for 20 minutes, then rinsed thoroughly, usually clears it. Avoid bleach or strong chemical cleaners - they can pit stainless steel over time.
Curious about the Thermoscup itself? See the Smart LED Flask.
