Low ABV time after time.

Discussion in 'General Brewing Discussions' started by ThatOldPC, Nov 9, 2015.

  1. ThatOldPC

    ThatOldPC New Member

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    Hey guys!

    I've been homebrewing for about five years but recently underwent some changes that put a two year pause in my brewing. Now I'm getting back into it. I've done two brews so far. Both have come out tasting well but I'm having a serious issue that I've never had before. My ABV has come out at half as high as it was supposed to both times. My Belgian wit was supposed to be about 6% ABV but came out just over 3% ABV. My Irish Stout was supposed to be about 7.5% ABV but came out at 4% ABV. Both were all-grain batches. 5 gallons per batch. Both batches sat a little longer in secondary fermentation by roughly 5 days. I have no idea what may be causing this problem.

    Any help or info would be appreciated! :D
     
  2. Ozarks Mountain Brew

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    sorry but your going to have to give more info, recipe, how you brewed it in detail, that would help us a bunch
     
  3. jeffpn

    jeffpn Well-Known Member

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    Have you brewed all grain before? What was your mash temp? Is your thermometer accurate? Did you ensure that your gravity reading has remained unchanged for a 3 day period?

    Those questions will get you started.
     
  4. ThatOldPC

    ThatOldPC New Member

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    Hello again,

    So I've been brewing all-grain for a long time, but this problem has never happened before. I've moved to a new home and location, so I'm still getting my brewing equipment settled in and figuring out the best way to utilize all of it in the new home. I brewed this as an Irish Sweet Stout. When brewing I mashed-in at 150 degrees (F) for 75 minutes and maintained that temperature the whole time using an electric induction plate on the lowest setting. I occasionally stirred the grain but only just to make sure I got full utilization. I routinely check my thermometers to make sure they're working right, no issues there. When I programmed the recipe into the website and on Beersmith this was the brew steps that popped out. I took my OG reading right before putting the wort in the fermenter. After that I didn't check it until it was time to rack over to the keg.

    One odd thing that has never happened to me before when brewing stouts, or any beer for that matter, was that less than 24 hours after pitching my yeast the wort bubbled up so much that it shot an 8 foot geyser out the top of my airlock and covered my ceiling. The airlock stayed on though and I was able to sanitize and setup a blow-off tube to replace the airlock. 24 hours later the wort barely bubbled the water in the bucket of my blow-off tube at all. It I let it sit for the full 5 days in primary and 7 in secondary. In secondary it had 7 extra days tacked on because my keg's o-ring failed before I transferred and I had to wait to get a new one. So total fermentation time was 19 days!

    While racking it over to the keg I sampled it and checked the gravity to get my final reading. The post-boil target gravity was 1.069 OG, I hit my target perfectly at 1.069. When I did my FG reading it came out to 1.037 G. According to the calculator on BF it comes out to 4.07% ABV, whereas my target was 7.5% ABV.

    Any ideas?
     
  5. Ozarks Mountain Brew

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    that makes sense, you lost most of your yeast out the airlock and didn't get the attenuation you needed to finish fermenting, Ive had to move to a much larger fermenter for the same reason, I use a 12 gallon fermenter even for 5 gallon batches, in most of my beers I have very strong activity and an airlock just wont work
     
  6. ThatOldPC

    ThatOldPC New Member

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    That explains that.

    Next question: I've got a 6.5 gallon glass carbory that I use as my primary fermenter. Is there any way to keep this from happening without a very costly upgrade?
     
  7. Ozarks Mountain Brew

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    try to ferment cooler, like 60
     
  8. jeffpn

    jeffpn Well-Known Member

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    Find a tube that slips over the part of the airlock that the bobble sits on. Run the other end of that tube into a bucket of water. Do that until fermentation settles down.
     
  9. The Brew Mentor

    The Brew Mentor Well-Known Member

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    1st of all, I believe even after blow off, there'd be plenty of yeast to finish the job. Brewers Krausen their beers for yeast collection all the time.
    Next questions would be your recipe, fermentation temperature and yeast type?
    Brian
     
  10. Ozarks Mountain Brew

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    this happens with high flocculating yeast, had a streak of this happen to me one year,what happens is some or half flocs to the bottom while the other half goes crazy at the top, if most of the top blows out then the bottom stays clumped unless you shake it up or stir it to get it going again but keep in mind it will have to reproduce more cells and it will seem to do nothing for a few days but in fact its basically starting over so you've wasted 3 days
     
  11. flars

    flars New Member

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    Are you using a hydrometer or refractometer for FG? Refractometers are not accurate for FG because of the presence of alcohol. Check SG with a hydrometer before you racking to the secondary vessel. An incomplete fermentation may stall if racked before FG is reached.
     

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