Whenever I take a SG reading with my hydrometer I have a hard time getting an accurate reading because of a few mm of foam at the surface. Does anyone have any suggestions on how to get rid of the foam?

7 Answers 7


You can try filling the tube up to (or at least close to) the top, so that when you lower the hydrometer, most of the foam spills over the edge. Once it's that high up, it's not too hard to blow most of the remaining foam off.

Don't forget though to give the hydro a dunk and spin to dislodge any bubbles stuck to the bottom of the hydrometer from an excessively carbonated sample.

  • 1
    I might have to chop a few inches off my test jar, but I love the simplicity of this. Commented Dec 15, 2011 at 18:13

While @tallie's overflow answer is excellent, you can also just wait. I take my sample into a footed hydrometer test jar. Set it aside and do other brewery things while the foam settles.

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  • Hah, looking at your hydrometer I think mine is ~6 inches longer than it needs to be. I need ~4 or 5 hits from the beer thief before mine gets close to full. Maybe I'll cut a few inches off the top... Commented Dec 15, 2011 at 18:09

Patience helps. I give the hydrometer a spin in the wort which helps it settle without influence from the bubbles/foam. Depending on how dark the beer is I can usually read it from underneath the foam through the beer.


Get a refractometer. The advantages are many, and include the fact the foam and carbonation are irrelevant to the reading. Lots of cheap ones available on eBay.

  • I've never used one, but isn't there some math you have to do to make the readings accurate if there's alcohol in the solution? Seems like a pain.
    – GHP
    Commented Dec 15, 2011 at 13:39
  • If you're already using brewing software it'll almost certainly have a hydrometer calculator. Enter the OG. Enter the SG of your reading and the calculator will adjust for the alcohol present and tell you the amoune of residual sugar. Commented Dec 15, 2011 at 15:50

I'm using a turkey baster to extract my wort/beer, I always slowly drain the beer out into the plastic hydrometer cylinder to decrease the amount of foam. I always like to give it time to sit and get to room temp, this should give it time to de-gas. I also like to take a test sample when it's warmer for a better idea of the flavor.


I just pour the sample between two containers a few times and the gas dissipates. Its not like the beer is really carbonated, so it goes flat with a little disturbance.

Make sure you taste it too:D!


for the most accurate reading, it's always good to gas off some of the co2 by pouring the beer from glass to glass a few times and then filling the hydrometer all the way to the top so the foam overflows, as Tallie says.

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