Hydrometer readings

Discussion in 'General Brewing Discussions' started by EvanAltman36, Oct 30, 2013.

  1. EvanAltman36

    EvanAltman36 New Member

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    Ever since I started using my wine thief, I've noticed that both my OG and FG readings are higher than anticipated, so I wanted to throw a couple things out there. In the past, I had used a turkey baster to remove samples and I then measured in the hydrometer tube. The baster fell apart and the tube required a relatively large sample, so I went with the thief. But, alas, the readings seem to be off. My earlier batches were all hitting very close to my target FG, but I've not been hitting it lately; despite the seemingly high numbers though, the taste and feel of my beers has been great. And I can guarantee that the alcohol isn't too low.

    Also, this has been the case regardless of pitch rate; even when I was only pitching 1 packet I was hitting FG. Now with 2 or 3 I'm still not getting there.

    My initial thought was that the OG samples could be high because I didn't stir well and the thief was pulling from the "heavier" part of the wort. But that difference should be diminished in the fermented product, which hasn't been the case.

    So I'm thinking that the decreased diameter of the thief, relative to the original hydro tube, is the culprit. Any bubbles in a smaller space would create more buoyancy, right? And I've also read that the electrostatic attraction from glass to plastic can also throw off the readings. For whatever reason, I haven't checked it against plain water to make sure it's accurate, but I'm looking for some thoughts. I may just opt to use the thief to gather and the old tube to measure.
     
  2. chessking

    chessking New Member

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    Find out for yourself. Take a reading in the thief tube, then pour the same sample into the original hydrometer tube and take another reading.
     
  3. grainy one

    grainy one New Member

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    If I had to guess at what's happening to your readings it would be the electrostatic attraction from glass to plastic or the size of the beaker , different diameters different surface tension . Wish I had two different sized beakers so I could test this out . good luck.
     
  4. NTexBrewer

    NTexBrewer Member

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    I would do as suggested and read it in both vessels to see a difference. Also, make sure you use RO or Distilled water to calibrate your hydrometer. At least for me Tap water gives me a different reading.

    I have a mental picture of the type of thief you are using. It has a needle valve at the bottom to fill and hold the sample and you can place the hydrometer in the thief. I wonder if some error can be introduced since you have to hold the thief to take your reading.
     
  5. EvanAltman36

    EvanAltman36 New Member

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    Yeah, I'm sure the thief introduces too many variables to be accurate. Given the narrow diameter, it's really difficult to get the hydrometer to float straight. I'll run some tests tonight and see what I come up with, but the fact that my readings have been off ever since moving to the thief are a good indicator. I'll still be able to use it to pull samples, but I'll probably stick to the bigger vessel for the hydrometer.
     
  6. Nosybear

    Nosybear Well-Known Member

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    I use a plastic sample jar then taste or discard the sample. If I were looking to a problem, I'd look to stratification, particularly in the OG samples. The thief is reaching lower into the wort than your turkey baster. The FG samples should be about right. And in the end, at homebrew scales, the actual gravity isn't that important, the difference between OG and FG is.
     

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