Wart Gravity Readings

Discussion in 'General Brewing Discussions' started by Group W, Mar 24, 2018.

  1. Group W

    Group W Well-Known Member

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    Well, I need a little help getting pre-boil and during-boil gravity readings. I use a refrac to test, and yes it is calibrated, matches my hydrometer, and I’m careful about temp of the sample and refrac.

    Those early readings are usually high which freaks me out a little. But when the boil is finished and cooled to pitch temp, my OG number is usually spot on.

    Are there likely suspended solids making those early readings high, or what?

    Thanks :)
     
  2. Ozarks Mountain Brew

    Staff Member

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    the preboil is reliant on your mixing of the wort right before the boil which most people really don't to very well and the amount of water you add or sparge with.
    there are so may things that can be a little off its just not a good thing to match so I wouldn't worry too much on it, if your final readings are fine your good, thats all that matters
     
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  3. Mase

    Mase Well-Known Member

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    Never thought about solids affecting the readings, so I can’t answer. For what it’s worth, I take readings of first runnings ( don’t really know why I do, but I do), but once I have preboil volume, I thoroughly mix (as Ozarks points out), and take a preboil gravity. I can reliably add 11 points and that will be my post boil gravity (assuming no sugar additions during boil). My preboil volume is at a bit over 6.5 gallons and shoot for just under 5.5 gallons post boil. Temperature of wort at gravity reading does affect the reading, so I shoot for right around 65-70 degrees (f) before taking a reading.
     
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  4. Group W

    Group W Well-Known Member

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    I mixed the pre-boil wart after collecting all of it in my BK. I got 1048 and had a OG target of 1050. I just wanted to see if I was hitting the BF recipe of 1039.

    I agree on RDWHAHB at that point. Perhaps just dip some out with a shot glass, let it cool and settle out, then take the reading...?
     
  5. Group W

    Group W Well-Known Member

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    Perhaps there’s another explanation. I brew in an unheated shop. It was 22 df here last night. It took an hour to heat the shop to 55 df. I put the refrac (in it’s case) near the propane burner while my HLT heated. I moved the refrac away when the case was very warm. But the case is insulated with foam. I opened the case and removed the refrac while mashing. Ambient air was 55 df when I started mashing. I’m thinking with the thermal mass of the refrac it was still cold after the mash (pre-boil). IDK, maybe all will be good come summer. :confused:
     
  6. Bowhunter64

    Bowhunter64 Member

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    I fly sparge most of my brews so I'm pumping weaker wort into the bottom of the kettle so when I get close to my pre boil volume I stop and mix well before I test an then start again until I hit my BG regardless of boil volume which almost always runs over estimated volume.
     
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  7. J A

    J A Well-Known Member

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    I've never gotten pre-boil gravity measurements that added up right when compared to the OG post-boil with the proper volumes in the equation. I depend on actual post-boil, post-chiller gravity for OG and that has been very consistent whether measured right as it's going into the fermenter or left overnight to settle. For estimating gravity during mash, sparge and boil, I get refractometer readings that will tell me if it looks like my efficiency is pretty much on track and sometimes take hydro reading just to see what it is. The hydro is always higher than it should be but I can compare to refracto readings and check the trend.
    Safe to assume that boil off in the typical 25% range raises the gravity around 10 points. Accurate post-boil gravity and volume readings will confirm your efficiency percentage and if you have accurate pre-boil volume your gravity can be accurately extrapolated. Compare that with your pre-boil gravity readings and you'll get an idea of how accurately you can estimate while you're boiling.
     
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  8. Jim P

    Jim P New Member

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    New to this forum. My question is when I take OG reading I am spot on. After two weeks in Primary Ferment Im at 1.024 and target at 1.009.

    I just dont think it will get there laagering at 40 degrees for another four weeks. Can/should I re-pitch to lower FG????
     
  9. jeffpn

    jeffpn Well-Known Member

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    What temp did you ferment at? The way I’m reading your question, you’re already at 40°. You won’t see a drop in gravity at that temp.
     
  10. Nosybear

    Nosybear Well-Known Member

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    If I'm reading your question correctly, you dropped your beer's temperature to 40 degrees before hitting your final gravity? If that's the case, warm it back up and let the yeast finish its job. Other possibility: Are you getting 1.024 as an FG with a refractometer? If so, you'll have to correct the reading. I use a correction spreadsheet and when I do so, 1.024 on a refractometer converts to a SG of about 1.010, depending on the original gravity of the wort. There's also a refractometer correction calculator on this site. Or take the FG reading with a hydrometer, that one isn't sensitive to alcohol content in the same way as a refractometer.
     
  11. Jim P

    Jim P New Member

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    Fermented at 58 for two weeks now and took reading and got 1.024 with a OG of 1.040, target is 1.009. Temp at 54 now.
     
  12. Jim P

    Jim P New Member

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    Fermented at 58 for two weeks now and took reading and got 1.024 with a OG of 1.040, target is 1.009. Temp at 54 now. How do I get to 1.009???
     
  13. Nosybear

    Nosybear Well-Known Member

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    Did you use a refractometer to take the reading that got you 1.024? A beer that small should not have stalled, provided you didn't pitch too hot or fail to oxygenate. If you took the gravity after the beer has started fermenting with a refractometer, it will give you an incorrect result. Hence my question: Did you take the gravity reading with a refractometer? If you did, you don't have a problem with the beer, rather with the gravity reading and if that's the case, you may already be at the FG you want. But if you want another test, take a sample and taste it. If it's sweet, you still have sugar to ferment. If not, recheck your gravity readings and correct the refractometer reading.
     
  14. Ozarks Mountain Brew

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    I probably should post this somewhere else but its a topic that covers some of the things mentioned here, take a look
     
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