Does it make sense to salt water after it boils? On the one hand, salted water has a higher boiling point. On the other hand, it increases regardless of whether you salt at one point or another 🙉
As @Sneftel wrote, the amount of salt used in cooking will not change the boiling point of water by any appreciable amount. However, if you are adding salt to water for flavor or other purposes, there is a good reason to add salt only once the water is boiling (or at least hot), especially if you are using a stainless-steel pot.
Salt crystals left undissolved at the bottom of a pot of cold water can corrode the stainless steel of the pot and result in pitting and discoloration. If you add the salt only once the water is hot/boiling, it will dissolve right away and not sit at the bottom to cause corrosion.
1I don't understand this argument. Unlike sugar, salt dissolves at the same speed in both cold and hot water. So, how does adding it to boiling water protect the pot?– rumtscho ♦Jan 27 at 13:53
I'm also not buying the whole "salt damages the stainless steel pot" thing. Not only have I made pasta in salted water for the last 20 years with no visible damage, I've even cooked things like salt potatoes in it, which require a supersaturation of salted water. Gonna open this as a new question. Jan 27 at 19:47
Update: we already have a really good answer on the salt-in-pasta-water thing, and the answer documents that it's a myth: cooking.stackexchange.com/questions/30253/… Jan 27 at 19:51
The boiling point of water is not significantly affected by adding normal quantities of salt. If you’re just trying to change the boiling point of water to the point where it has an effect on cooking, it doesn’t make sense to add salt before or after it boils.
Adding salt to the water doesn't change the boiling point that much, as stated in other answer.
There is one reason for adding salt after the boiling: in stainless steel pan, the chloride from the salt can in the long run damage the steel. This effect is more pronounced with higher concentration of chloride, thus leaving the clump of salts at the bottom of the pan while the water eats up helps this higher concentration build up, together with giving more time for the chloride to work.
Stainless steel is often used in reinforced concrete structures, as despite being one of the most affordable structures, reinforced steel has poor durability. This lack of durability is exacerbated in severe conditions such as those in contact with oceans, de-icing or other chloride-contaminated environments. On the surface of steel, a thin oxide layer forms following exposure to an alkaline medium. When this layer is exposed to a large concentration of chloride ions it can be destroyed.