Miele H6500BM Operating And Installation Instructions page 17

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The boiling rod ensures that the liquid heats up evenly with
bubbles forming at the right time.
When reheating liquids, always place the boiling rod supplied into
the cup or glass.
When boiling and in particular when re-heating liquids, milk, sauces
etc, using microwave power without the boiling rod, the boiling point
of the liquid may be reached without the production of typical
bubbles. The liquid does not boil evenly throughout. This so-called
'boiling delay' can cause a sudden build up of bubbles when the
container is removed from the oven or shaken. This can lead to the
liquid boiling over suddenly and explosively. Danger of scalding and
burning. The formation of bubbles can be so strong that the
pressure forces the oven door open, with a danger of injury and
damage. The user could be injured and the appliance damaged.
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Eggs can be cooked without their shells using microwave power
only if the yolk membrane has been punctured several times first.
The pressure could otherwise cause the egg yolk to explode.
Warning and Safety instructions
17