Most Mums are always worried about the milk spilling during the boil. Let’s see why this happens!
Why does Milk overflow when boiled but Water doesn’t?
Before we start, we must be aware of that fact that milk is not a normal liquid like water. Milk is far more complex as it is made-up of 87 percent water, 4 percent proteins and 5 percent lactose. When we boil milk, fat, sugar, proteins and minerals get separated.
As these are lighter than milk, they collect on the surface to form the cream.
Now, as the milk continues to get heated, out of the 87 percent of water, some of it gets converted into vapour. These bubbles of vapour start to rise above but are stopped and not allowed to escape by the cream which has been formed on the surface.
But this does not stop the vapour from forming. So as more water evaporates, more vapour and pressure builds up in the boiling milk.
Finally, the milk pushes the creamy layer out so that the air can escape. This then causes the milk to spill out of the vessel.
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