Can you put an insulated bottle in the dishwasher?

A vacuum flask keeps drinks hot because of a sealed vacuum between two steel walls. On older or cheaper designs, the seal at that joint can fail under sustained dishwasher heat, air enters the gap, and the bottle permanently stops insulating — it looks identical and simply no longer works. Most current brands have redesigned for this and mark the base dishwasher safe. Powder-coated exteriors are a separate issue and often fade or peel regardless. Lids with rubber gaskets should be dismantled and washed separately either way, since that is where mould actually grows.

How to do it properly

1. Look for a dishwasher-safe mark on the base.
2. Top rack only, and skip the heated dry if you can.
3. Take the lid apart and wash the gasket separately — that is where mould forms.

Other options

• Hand wash with a bottle brush; for stubborn odour, soak with bicarbonate of soda overnight.

Other "can you dishwasher" questions

• Can you put cast iron in the dishwasher? No — No. Dishwasher detergent strips the seasoning and the pan rusts within hours.
• Can you put knives in the dishwasher? No — No, if you care about the edge. Heat, detergent and knocking all dull and damage it.
• Can you put non-stick pans in the dishwasher? It depends — Only if the maker says so, and it still shortens the coating life considerably.
• Can you put wooden spoons in the dishwasher? No — No. Prolonged soaking and heat raise the grain, then crack and split the wood.