Can’t hit OG, but pre-boil gravity is fine...

Discussion in 'Beginners Brewing Forum' started by Brewer #91408, Jan 17, 2018.

  1. Jane Barnes

    Jane Barnes New Member

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    Hello wise brewers I was wondering if I could ask a question, see if anyone has any advice. I seem to be consistently missing my OG by a considerable amount, even though my pre-boil gravity is accurate based on the calculation from my recipe on Brewers Friend app.

    Figures for the last 3 brews (figure in brackets is calculated OG on recipe builder):

    Beer 1, pale ale
    Pre-boil gravity - 1.023, OG - 1.031 (1.044)

    Beer 2, pale ale
    Pre-boil gravity - 1.018, OG - 1.035 (1.050)

    Beer 3, stout
    Pre-boil gravity - 1.021, OG - 1.031 (1.059)

    After beer 2 I did an efficiency calculation and calculated it as 60% (I had been working to 70% previously).

    Any thoughts would be very much appreciated, thanks!
     
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  2. Ozarks Mountain Brew

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    I think I've said this before, not sure where but the pre-boil gravity is not a consistent reading, too many things can change that reading so I wouldn't use that as a standard source, you should use the original gravity in the fermenter for the best reading
     
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  3. philjohnwilliams

    philjohnwilliams Well-Known Member

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    Can you post a link to a recipe? Looking at you calculated pre and post boil gravities, it seems to me that the difference between them is way higher than any of my recipes. I usually see a .006 gain in gravity from pre to post boil, while you seem to expecting a change of .02 to .03. In your beer #2 with a pre boil gravity of 1.018 and an expected post boil gravity of 1.050, you would have to be starting with something like 14 gallons of wort and boiling off almost 9 gallons.
     
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  4. Hawkbox

    Hawkbox Well-Known Member

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    Yeah if i get a real good boil going I might gain .010 but not much more and that boils off a gallon or so of liquid.
     
  5. J A

    J A Well-Known Member

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    Pay no attention to Pre-boil.
    You don't include pre and post-boil volumes or the method you're using and there's no way to tell what's going on without those. Just from your figures, I'd say you're either sparging way too much or or not using enough in the malt bill to start with or both.
    Just calculate your boil off, be sure you sparge enough to get that volume and not a lot more. Ignore the Pre-boil gravity, hit your post-boil volume, check the gravity after the entire batch has cooled, calculate your efficiency based on that. Then you'll know how to build your recipes to fit your system.
    Almost any grain bill and method will give you more than 60%, so something is wrong. A lot of things can have a bearing on mash efficiency. PH being a biggie. Then there are a bunch of little things that can go wrong - I once had a leak in my immersion chiller that was diluting my wort...when I fixed it, I got better numbers and better beer. :)
     
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  6. Jane Barnes

    Jane Barnes New Member

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    Thanks for this! So should I disregard the pre-boil gravity and assume that my mash is not efficient? Up until now I had been thinking it was to do with the boil...
     
  7. Jane Barnes

    Jane Barnes New Member

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    Yes that is quite extreme isn’t it! Here’s links to the recipes:

    Beer 1
    https://www.brewersfriend.com/homebrew/recipe/view/510011/pale-ale-citra

    Beer 2
    https://www.brewersfriend.com/homebrew/recipe/view/589830/pale-ale-citra-v2-5l

    Beer 3
    https://www.brewersfriend.com/homebrew/recipe/view/592620/irish-whiskey-stout

    Any thoughts would be much appreciated, thanks!
     
  8. Jane Barnes

    Jane Barnes New Member

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    Ah yes, sorry. It's all grain and I only noted pre/post boil volumes in recipe 3, they are pre-boil: 14L, post-boil 10.8L. I'm aiming for 5L in the fermenter so its clearly way too much, but I've not wanted to carry on boiling it as it would mess up all my flavour/aroma hopping.

    I've measured post mash pH for beer 1 and 2 and they've both been 5.3/5.4 which I think is pretty good.

    I had the immersion chiller leak too! So annoying - I couldn't work out why I ended up with more beer than the amount of water I'd started with! A couple of new jubilee clips soon sorted it but I did ruin 2 brews...

    Thanks so much for your help.
     
  9. J A

    J A Well-Known Member

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    Obviously, if you're using grist for a 5 liter batch and you're mashing and sparging for a batch twice that size, you're not going to do any good. Why would you use such a large mash/sparge volume? Since you know what your boil-off is, adjust your liquor volumes to get that amount. And, no, you can't continue to boil.
    Adjust your volumes to proper level and you'll be fine. ;)
     
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  10. Jane Barnes

    Jane Barnes New Member

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    I was just going by the water requirements as recommended by Brewers Friend (see screenshot upload) but you're right, I can adjust these to my requirements based on these past 3 boils, that makes total sense.

    Thanks so much!
     

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  11. J A

    J A Well-Known Member

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    The water requirements come from equipment profile settings that, in your case, is way off - for instance, you're got a kettle dead space loss of almost half your batch size and your boil off is set very high for the volumes that you reported. Just do the math and brew a proper beer and then figure out your actual losses, etc,over the course of a few brews so you can adjust your equipment profile and things will match up. If you're brewing a small batch on a large system, your brewhouse efficiency will suffer, so you have to adjust accordingly.
     
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  12. Jane Barnes

    Jane Barnes New Member

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    All makes total sense. Can’t believe I didn’t see this myself

    Interesting about efficiency, I’m brewing on a 25 litre kit but just doing small batches as I’m short of time with a baby.

    Really appreciate all your help, thank you!
     
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  13. Hawkbox

    Hawkbox Well-Known Member

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    Your chiller leaked? Damn that's unfortunate.

    Based on what I played around with on a copy of your recipe you probably want to start with around 11-12L of water, not 18. I didn't really mess with anything else but I'd suggest just dropping your water levels and you will be off to a better start. Looks like you would probably want to reduce your grain bill some too.

    https://www.brewersfriend.com/homebrew/recipe/view/595741/pale-ale-copy

    Edit: The recipes otherwise look rather tasty.
     
  14. J A

    J A Well-Known Member

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    It'll work just fine, but just be prepared to deal with boil-off and losses which are usually bigger in a larger system. Once you start mashing and sparging in the proper amounts, you'll be on the right track.
    ;)
     
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  15. Shawnw116

    Shawnw116 New Member

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    I've been working with the same problem on all of my brews. Each batch hits the "Pre-boil" volume and specific gravity, but misses the mark completely on the "expected final" gravity.
    My volumes to the fermenter are spot-on and my equipment dead space and losses have all been calculated. I'm not sure why they would have a "Pre-boil" estimate in the calculator if it's not something we can count on...?
     
  16. Shawnw116

    Shawnw116 New Member

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  17. Ozarks Mountain Brew

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    the preboil is an estimate because too many ways to not get a true reading, meaning human error, one way you sparged to much or not enough, your mash efficiency was low or high, you didn’t mix up the wort enough before boiling creating erratic readings, the estimate is based on a perfect brew and face it, no two brews are identical
     
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  18. Shawnw116

    Shawnw116 New Member

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    Thanks, Ozarks
    I guess it's easy to fixate on target numbers and miss the other stuff. If I disregard the "pre-boil gravity" then my efficiency is closer to 54%.
    I think I'll work on getting better conversion in my mash and dial in my water volumes (boil-off rate, etc...) more accurately to see if that helps.
     
  19. J A

    J A Well-Known Member

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    Post a link to the recipe. No reason that you shouldn't be getting better efficiency with almost any method.
    And remember, you never lose sugar in the boil. Whatever sugar goes into the kettle stays there throughout the evaporative process. The only way to lose sugar is to leave it behind in the form of uncollected wort. Since the reverse is true, you can count on accurately computing the actual pre-boil gravity based on accurate pre and post boil volumes and the post boil gravity (which is inherently more accurate).
     

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