Erupting pot of hot water!

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Joined Apr 28, 2009
Hello,
I need a professionals opinion...

I put a pot of water on to cook some pasta and after it came up to a boil, I shut it down because something came up. Later on, I returned it to heat and just as it was coming to a boil, I added my salt and I suddenly discovered how people felt when mount Vesuvius erupted.

It exploded all over the stove, put the flame out and scared the hell out of the bystanders!

Someone please tell me what just happened.

Red
 

phatch

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The salt has a lot of reaction surface (nucleation sites) that can trigger the water to boil briefly if it's close to the boiling point. Once the salt is dissolved it actually raises the boiling point little bit.
 
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Not that I don't believe you but I just tried a little experiment because I've never seen anything like that. I heated some water in a saucepan to 208 deg F then threw in some kosher salt. Nothing happened. The salt just dissolved like it always did for me. What kind of salt did you use. And are you sure it was salt?
 

phatch

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Surfaces can aid in the transition to steam. Notice how the boiling action concentrates on the pin or the stick. If you have an old scratched of pot and boil water in it you will see that the water first bubbles and boils along the scratches.

A technical explanation https://www.physicsforums.com/threads/boiling-water-salt.8159/

The starchy water probably also contributes with foaming action.
 
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I understand what you are saying and the effect but I'm just not seeing the situation that the OP describes. I'm thinking too that the water had the pasta in it, it was starchy and the pot was too full. It was the foam that erupted. However the OP makes it sound like it was plain water. The story just doesn't make sense.

If adding something to or stirring boiling water resulted in a violent reaction we would be a well aware of the caution not to do so.
 

phatch

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I only get a brief kind of carbonated effect when I do it in water about to boil.
 

pete

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The question for the OP is, did the water "foam" up or did it bubble violently? I am wondering if your pot was actually properly cleaned after the last use. What you describe can happen-the internet if full of stories of people burning themselves with water, that they nuked, that explodes when they pull it from the microwave. This could be the same type of thing, but highly unlikely. If it bubbled up violently then this is probably what happened, but it if foamed up then chances are what your pot was not clean or there was something in the water that allowed the water to foam up when the salt was added.
 
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It bubbled over because when pasta soaks in water and is then reheated, it will almost certainly cause foam or bubbles to form on the surface of the water. Starch from the pasta makes the bubbles and foam more elastic which means the bubbles last longer. The longer the bubbles last, the more heat they trap between the water and the bubbles which can cause the pot to erupt with hot bubbles and boil over.
 

pete

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It bubbled over because when pasta soaks in water and is then reheated, it will almost certainly cause foam or bubbles to form on the surface of the water. Starch from the pasta makes the bubbles and foam more elastic which means the bubbles last longer. The longer the bubbles last, the more heat they trap between the water and the bubbles which can cause the pot to erupt with hot bubbles and boil over.
By the sound of the OP the pasta was never put in the water.
 
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I put the salt in the pot first then the water. By the time it comes to the boil it's all dissolved.
 

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