1. You can use 60 ml (2 oz) of white vinegar mixed with 120 ml (4 oz) of cold water to descale your bottle warmer.
2. Pour the solution into the bottle warmer.
3. Switch on the bottle warmer and select the milk-warming setting for contents under 180 ml (6 oz) setting and let the appliance operate for 10 minutes.
4. Leave the solution in the bottle warmer until all scale has dissolved.
5. Pour away the solution and rinse the warmer with tap water. If you still see traces of scale after rinsing, repeat the descaling procedure.

Note: you can also use citric-acid-based descalers.
Note: don't use any other types of descalers.