Why do I need to know surveiller comme le lait sur le feu ?

It's common, but also timely for what's happening in France right now.

What does it mean ?

Surveiller comme le lait sur le feu literally translates to ‘to watch like milk on the stove’, but French people use it about 'keeping a very close and vigilant eye on something'.

Milk, as you may have experienced, boils over very quickly if left on the stove for too long.

If you have ever had to wipe sticky milk off your stove and scrape burnt traces off your pan, you will immediately understand the meaning of the expression. 

The idea of surveiller comme le lait sur le feu is that something could go wrong at any moment, and possibly at the very second you are not watching.

The expression can be used about a situation that easily can take a turn to the worse without close surveillance. It captures well the French government's strategy when it comes to closely watching the Covid-19 virus' development in the country, monitoring the rates in detail every day on a local level.

But it can also be used about a person, and it's commonly used to talk about young children.

Use it like this

En tant que baby sitter, on m’a souvent dit de surveiller les enfants comme le lait sur le feu – As a baby sitter, I was often told to keep a close eye on the children.

Les cas de Covid se multiplient en France, le gouvernement surveille les chiffres comme le lait sur le feu – The number of Covid cases keep rising in France, the government is watching the figures extremely closely.

Andréa avait beaucoup trop bu à la fête hier, j'ai passé mon temps à la surveiller comme le lait sur le feu – Andréa drank way too much at last night's party, I had to tail her all evening to make sure she didn't get into trouble.

Synonyms

Surveiller attentivement– To watch like a hawk

Avoir l’œil sur quelqu’un/quelque chose– To keep an eye on someone/something