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Large Bubbles in Syphon / Vac Pot

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  • Large Bubbles in Syphon / Vac Pot

    Does anyone have suggestions for preventing large bubbles / turbulence from appearing after the water rises into the upper chamber?
    I get large bubbles forming about 50% of the time, and I notice that the brew tastes "ashy" if coffee is brewed when these large bubbles are present.

    Suggestions on other websites say that if such bubbles appear, it is best to adjust the filter to keep the bubbles from forming. If that fails, then start all over and make sure there are no leaks in the seal. Ive done this, but I still get large bubbles.

  • #2
    Re: Large Bubbles in Syphon / Vac Pot

    Sounds like way to much heat. As soon as the water starts to rise up back the heat off to just get the water to the top chamber. Depending on the Syphon you should be able to get it done at 92-93 degrees reliably. If you leave the heat up and have a rapid boil going on at the bottom you will get the larger vapour bubbles in the top and you can easily get over 95 degrees in the top.

    Do you have a milk thermometer or better yet a digital meter of some sort and do some dummy runs to check the temp.


    • #3
      Re: Large Bubbles in Syphon / Vac Pot

      bean is right: once the water goes up you want the heat to be just enough to stop it from drawing back down- and no more. This can be harder to control if you are using one of the alcohol type burners. If you use a butane burner it is easy to turn it down after the water goes up.

      It is also easier/faster to start with hot water from the kettle.


      • #4
        Re: Large Bubbles in Syphon / Vac Pot

        Thanks for the replies. Ive experimented with cloth and paper filters, and I noticed that stopping the bubbles from forming is easier when using a cloth filter. I just move the filter a little bit with the wooden spoon. If I try this with a paper filter, a new set of bubbles forms on the other end of the filter!
        Ive also tried keeping the water temp as low as possible (using a butane burner) as the water goes north (I attach the top part of the syphon when the water in the bottom reaches 97-98C), but it still does not help that much.
        Sometimes if I just let it sit for a couple of minutes, the bubbles go away on their own. But then the water temp above drops to the low 80s.
        I made 2 syphons today with using Yirgacheffe beans. The brew without bubbles tasted like blueberry cheesecake, while the brew with bubbles up top tasted like burnt blueberry muffin.


        • #5
          Re: Large Bubbles in Syphon / Vac Pot

          I just posted a short video on youtube of what Im experiencing with these bubbles.


          • #6
            Re: Large Bubbles in Syphon / Vac Pot


            just had a watch of the video.

            You need to start cutting back the heat from the burner as soon as the water starts to rise. With the butane burners it is easy as they can be adjusted. With the alcohol ones a simple slide to the side so that less of the flame is in contact with the residual water.

            The paper type of filter holder you are using I have on a few of mine Syphons but I prefer the Hario cloth ones without the centre pin. While this wont be causing the bubble problem they work better and are easier to clean.

            Have a play with the burner I reckon


            • #7
              Re: Large Bubbles in Syphon / Vac Pot

              What type of burner is that you are using?

              also the bubbles dont look too bad... and certainly no where near as big as these bubbles:




              • #8
                Re: Large Bubbles in Syphon / Vac Pot

                @sorrentinacoffee Hahaha! I almost spit out my coffee in laughter when I clicked the link thinking it was going to be about syphon bubbles! I wish my syphon could do that. My daughter would be thrilled.

                Im using a butane micro burner.

                This is still my favorite failed syphon video of some gigantic bubbles forming in the upper chamber. The 1:00 mark is where youll find it.

                @beanflying I think you are spot on with regards to cutting back on the flame and using cloth filters.

                It looks like I may have found 2 answers to why I had so many bubbles forming on the sides of the filter:

                1) The spring connected to the bottom of the filter was worn and stretched from being used for so many months. It just wasnt as "springy" anymore. After getting a new filter, I still noticed that bubbles were still forming, although not as much as before, so...

                2) I compared the paper filter disk with some cloth filter disks (both metal and ceramic), I noticed that the diameter of the paper filter disk was a couple of millimeters shorter than the cloth filter disks. As a result, the paper filter setting was not producing a tight fit along the bottom of the upper chamber.

                Ive switched over to the cloth filter disks for now, and I hardly have any large bubbles anymore coming up from the filter casing.