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exploding duck stock -- why?

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I was making a very reduced duck stock as the first step to making duck terrine. Yesterday I made the stock and started reducing it but ran out of time so I refrigerated overnight. This morning I skimmed the very small amount of fat off the very gelatinous top and started reheating it to keep reducing it. It fully melted, I stirred it through, then a couple minutes later I walked by and took a look -- did not seem to be simmering or boiling -- as I got to the other side of the kitchen I heard a sound and turned to see the stock erupt like a geyser. I have never seen anything like it. Thank goodness I wasn't standing over it -- I'd be in the hospital right now, for sure. Does anyone know why that happened? The more I think about it, the scarier and more mysterious it seems.

Only a small amount of stock remained in the pan after it happened -- the rest was on the walls, floor, under the burners of the stove, etc (and just SOOOO much fun to clean up).

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  1. WOW! maybe you had the heat too high to start off with?????????? (just a guess)

    1. Oh, yes I remember reading about the technical explanation of this: IIRC, it has to do with surface tension of fluids like this. There is an article out there on this.

      1 Reply
      1. re: Karl S.

        It sorta sounds like the bubbling tomato sauce principle (except exaggerated about 1000x in this case).

      2. I think what you may have experienced is a case of nucleation and superheating. My knowledge of physics is sadly rudimentary but perhaps someone can explain it properly.

        As I understand it, when something is going from one state to another (say from a liquid to a gas) small bubbles first form in the liquid. They can meet and join together to form a huge bubble if the surface tension of the liquid cannot be overcome by the small bubbles. Then once the big bubble meets an imperfection in the pan or is somehow disturbed, kabloowie, geyserville.

        Correct me if I am wrong.

        2 Replies
          1. re: snackish

            I guess that's why they call it duck stock.

            DUCK!!

            ha.

            Link: http://meglioranza.com

          2. sounds like that urban legend about heating a glass of (filtered) water in the microwave--which is no myth.

            i wonder what kind of stock pot you were using. i understand that the smoother the lining of the pot the more it contributes to this phenomenon--and possibly having a tall, narrow pot.

            i think the fact that it was not simmering or boiling points to the whole thing getting superheated.

            1. It sounds like you all have come up with the answer -- thanks and especially to Karl S for the scientific reading. So it sounds as though much more stirring is in order next time -- and also maybe a bigger pot.

              I did duck, Tom, believe me!

              1. This happened to me just now with the stock I am making with 10 lbs of chicken backs. I only lost about a pint but for a while was wondering if my house was haunted since my bed was moved a half foot from the wall two nights ago while I was sleeping. The bed thing could however have something to do with the half bottle of wine I had before I went to bed.

                The stock had been going for almost two days. I was holding the broken up chicken backs in a deep insert that I guess most people would use for pasta. I heard an odd sound from the other room while feeding the rabbit. Then I saw the mess at the stove with a few choice words. I took out the insert and let the stock drain from the rubbish. I then set the heat back on.

                The broth sat still as the electric burner charged up. Then BLURP, I saw a surge come up from the bottom. It was dead center and carried with it anything that had sunk to the bottom. I had enough head room that it did not make a mess this time. This did not happen if I kept the broth moving and brought up the heat. I'm sure it has to do with the viscosity and depth of the broth as it is being heated from the bottom.