Measuring O.G pre and post boil.

Discussion in 'General Brewing Discussions' started by Stouter, Apr 4, 2017.

  1. Stouter

    Stouter New Member

    Joined:
    Dec 7, 2016
    Messages:
    7
    Likes Received:
    1
    Trophy Points:
    3
    Location:
    Geraldton
    I've been using the software and entering info which on my latest brew yesterday punched out an expected O.G of 1.050.
    During the brew I took samples pre-boil and post boil, cooled both overnight to pitching temp in the F.V fridge and measured today. Same temp, same hydrometer.

    Pre-boil came in at 1.050,
    Post boil came in at 1.060.

    Seems a such big difference, and now I'm not sure which to use for my O.G!?
    Does the boil produce/convert more sugars?
    Having never used these functions on the software before, or taken a pre-boil measurement I'm now confused.
    Also wondering if any trub or cloudiness in hyro samples would contribute to mismeasurements? While both of my samples were quite clear in this case, I've often thought it might give a higher reading if clouded.

    After punching all this in my brewhouse efficiency spat out at 78%.
     
  2. J A

    J A Well-Known Member

    Joined:
    Jan 19, 2016
    Messages:
    3,476
    Likes Received:
    2,694
    Trophy Points:
    113
    Location:
    Austin, Texas
    Specific gravity is a measurement of how much sugar is concentrated in the water...more sugar, higher gravity. You're not producing sugar in the boil, you're reducing the amount of water it's suspended in or concentrating it into a smaller space so the gravity goes up.
    The OG in the calculator refers to the specific gravity of the wort that you're going to pitch the yeast in - post boil.
    There's a little section called Batch Stats at the top right of the "More..." drop down tab in the calculator.You'll see "Boil gravity" at the top of that section...that's a calculation of the gravity of your wort before you start boiling. Depending on your boil-off rate, it's usually about 10 points lower than the OG (post boil) for the recipe.
    You're numbers make perfect sense...up to 80% efficiency is pretty common, depending on system and method and you probably boiled off about a gallon and an half for a 5 gallon batch.
     
    Trialben likes this.
  3. Stouter

    Stouter New Member

    Joined:
    Dec 7, 2016
    Messages:
    7
    Likes Received:
    1
    Trophy Points:
    3
    Location:
    Geraldton
    Of course, the water loss during the boil.
    So which reading (pre or post boil) is the software using for my expected O.G reading when I formulate a recipe?
     
  4. Trialben

    Trialben Well-Known Member

    Joined:
    Mar 30, 2016
    Messages:
    9,443
    Likes Received:
    9,513
    Trophy Points:
    113
    Gender:
    Male
    Occupation:
    Pest control tech
    Location:
    Palmwoods QLD
    Post boil stouter this is your OG
     
    J A and Stouter like this.
  5. Stouter

    Stouter New Member

    Joined:
    Dec 7, 2016
    Messages:
    7
    Likes Received:
    1
    Trophy Points:
    3
    Location:
    Geraldton
    Sweet as. So my O.G. was 10 points over what was predicted. I must be doing something right, or something dodgy :).
    Thanks for the help guys.
     
  6. nzbrew

    nzbrew Active Member

    Joined:
    Jan 7, 2014
    Messages:
    117
    Likes Received:
    44
    Trophy Points:
    28
    Did your volume come out as predicted?
     
  7. J A

    J A Well-Known Member

    Joined:
    Jan 19, 2016
    Messages:
    3,476
    Likes Received:
    2,694
    Trophy Points:
    113
    Location:
    Austin, Texas
    10 points is a big difference. If you calculated based on 60 percent efficiency and got 78 percent, that would do it. If not, it's totally likely that you're not accounting for something somewhere along the way. Either your volumes or your ingredient amounts aren't matching up to what the calcuator thinks you're using.
    Your boil-off/final volume would have to be off by a gallon in a 5 gallon batch to make a 10 point difference. My guess is that your original calculation was based on a much lower efficiency than you got. You'll be able to take that into account next time.
    If you're going for a particular OG and it's important to keep it under a certain amount, you can always add water back in and lower the gravity reading.
     
  8. Stouter

    Stouter New Member

    Joined:
    Dec 7, 2016
    Messages:
    7
    Likes Received:
    1
    Trophy Points:
    3
    Location:
    Geraldton
    The recipe is my Pale Nelson #2, which I think is marked as public for anyone interested. Trying to refine my #1 which was a very nice drop.

    Volume was good, filled the cube spot on.
    My original input of water was 36L, which I bumped up to from my first first few brews because I wasn't completely filling a 20L cube before getting down to the point where trub was getting sucked out at tap level (40L Crown Urn BIAB). A 20L cube filled completely with no air left probably holds more like 22-23L of hot wort I suppose, especially given the expansion. I should really test measure this out with some hot water before the next brew.

    I think the original eff estimate I entered was 65%(I'd have to check that), that was based on my previous attempts and slightly different technique with raising and draining my bag. My post boil OG readings seem higher on the last two brews after changing this method. This brew was also mashed at a slightly lower temp and longer than I usually would as I was trying to achieve a drier finish.
    Regarding keeping under the initial est O.G, I can add a suitable amount of water to the wort before pitching to alter this if needed.
     
    J A likes this.
  9. Mark D Pirate

    Mark D Pirate Well-Known Member

    Joined:
    Aug 21, 2016
    Messages:
    1,887
    Likes Received:
    1,280
    Trophy Points:
    113
    Occupation:
    Master carpenter , all round good guy
    Location:
    Radelaide SA , Australia
    Hey Stouter i also no chill and use a crown urn
    Are you using whirlfloc in last 10 mins of boil and run a whirlpool ? i start with 32 litres and fill my cube completely .

    You can also use your cube to oxygenate your wort before pitching by draining half of it in then re capping it and simply shaking it like it owes you money , i pitch yeast into FV first then pour wort on top so it doesn't get caught up in the foam but instead gets spread through whole wort evenly
     
  10. Stouter

    Stouter New Member

    Joined:
    Dec 7, 2016
    Messages:
    7
    Likes Received:
    1
    Trophy Points:
    3
    Location:
    Geraldton
    Yep, I do the whirl flock at 10 and whirlpool it. There's always a decent cone of trub, and what I leave behind is usually at about halfway down the tap outlet level.
    I've been oxygenating my wort with an oxy bottle and stone.
     
  11. Mark D Pirate

    Mark D Pirate Well-Known Member

    Joined:
    Aug 21, 2016
    Messages:
    1,887
    Likes Received:
    1,280
    Trophy Points:
    113
    Occupation:
    Master carpenter , all round good guy
    Location:
    Radelaide SA , Australia
    Our boil off rates must be drastically different then , or the markings for volume on yours are off
    36 litres strike plus 5 odd kg of grain would overflow my urn .

    Doesn't matter much as long as you're getting consistent results
     
  12. Trialben

    Trialben Well-Known Member

    Joined:
    Mar 30, 2016
    Messages:
    9,443
    Likes Received:
    9,513
    Trophy Points:
    113
    Gender:
    Male
    Occupation:
    Pest control tech
    Location:
    Palmwoods QLD
    So with the cube method hop particles are not good to carry over into the cube right? Grassy extra bitterness through extended isomerization yes? But cold and hot break material shouldnt be to detrimental mmmmyt?
     
  13. Mark D Pirate

    Mark D Pirate Well-Known Member

    Joined:
    Aug 21, 2016
    Messages:
    1,887
    Likes Received:
    1,280
    Trophy Points:
    113
    Occupation:
    Master carpenter , all round good guy
    Location:
    Radelaide SA , Australia
    You don't get much cold break with no chill , hot break will stay in urn and hop matter stays in urn

    I rely on the near boiling temps of the wort to ensure sanitary conditions in the cube , I've had cubes sit for a month
     
  14. Trialben

    Trialben Well-Known Member

    Joined:
    Mar 30, 2016
    Messages:
    9,443
    Likes Received:
    9,513
    Trophy Points:
    113
    Gender:
    Male
    Occupation:
    Pest control tech
    Location:
    Palmwoods QLD
    You see im a dump her all in type mark so thats why i was questioning trub in cube. I havent done mucb cubing last ine was about a year ago. I just like to chill her down and get that yeast working for me.
     
  15. Mark D Pirate

    Mark D Pirate Well-Known Member

    Joined:
    Aug 21, 2016
    Messages:
    1,887
    Likes Received:
    1,280
    Trophy Points:
    113
    Occupation:
    Master carpenter , all round good guy
    Location:
    Radelaide SA , Australia
    Considering how much hops I sometimes throw in the boil I doubt I'd want it all in the cube
     
  16. Trialben

    Trialben Well-Known Member

    Joined:
    Mar 30, 2016
    Messages:
    9,443
    Likes Received:
    9,513
    Trophy Points:
    113
    Gender:
    Male
    Occupation:
    Pest control tech
    Location:
    Palmwoods QLD
    Fairs fair me old mate yep I'm not that hopped up probably most hops I put in a brew at the moment would be 90g I'm yet to really cut my teeth so to speak on the hoppy side of brewing. But don't get me wrong I'm not shy of a few hop verietys thrown in a homebrew I've just yet to venture there.
     
  17. Mark D Pirate

    Mark D Pirate Well-Known Member

    Joined:
    Aug 21, 2016
    Messages:
    1,887
    Likes Received:
    1,280
    Trophy Points:
    113
    Occupation:
    Master carpenter , all round good guy
    Location:
    Radelaide SA , Australia
    many ways to skin a cat mate , we're all brewing on different systems with different goals
     
    Trialben and jeffpn like this.
  18. Stouter

    Stouter New Member

    Joined:
    Dec 7, 2016
    Messages:
    7
    Likes Received:
    1
    Trophy Points:
    3
    Location:
    Geraldton
    I reckon I might need to recheck all my containers. But I'm think they're all good. I did initially measure them all out, not relying on the stamped marks on the plastic.
    Next brew will tell.

    With the no chill side of things I've thought about siphoning off to transfer into the F.V, so whatevers settled out over the week, month, etc, might staying there, but I've just been chucking it all in. The majority of my brews have been Stouts and Ales, so haze or clarity isn't a big concern, get it in ya.
     
  19. Mark D Pirate

    Mark D Pirate Well-Known Member

    Joined:
    Aug 21, 2016
    Messages:
    1,887
    Likes Received:
    1,280
    Trophy Points:
    113
    Occupation:
    Master carpenter , all round good guy
    Location:
    Radelaide SA , Australia
    What break does precipitate in the cube should have 0 effect on clarity or stability, I do dose all my bright beers with polyclar during the cold crash and get brilliant results
    With dark beers its pretty much a non issue though
     

Share This Page

arrow_white