When to add salt to cooking water?

A recipe from cooking-ez.com

Times:

Preparation	Cooking	Start to finish
2 min.	10 min.	15 min.

Step by step recipe

• 1: 1 litre of water is put in a pan and 1 tbs coarse salt is added.
• 2: The water temperature is measured in the same way, every minute, until it boils.
• 3: Let's compare times and temperatures in this diagram: the unsalted water in green, the salted water in red.

Remarks

At the start of heating, the temperature of the salted water rises more slowly: after 3 minutes 30 seconds the unsalted water is already at 040°C (100°F), while salted water is still at 025°C (80°F).
But then the two catch up and they take the same time to reach 100°C (210°F).
Another point: it seems, but I'm not really adamant about it, that salted water starts to boil at a lower temperature than unsalted, i.e. around 90°C (190°F) rather than 100°C (210°F).

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