I missed my OG by 22 points but exceeded my pre-boil gravity

Discussion in 'Brew Sessions' started by DonY, Jan 11, 2015.

  1. DonY

    DonY New Member

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    I'm scratching my head on this one. This is my first attempt using brewersfriend recipe tools and brew session tools. I was doing a 5G Heady Topper clone AG recipe from NB scaled down to 2.5G.

    I ended up with 0.5G more for my pre-boil volume and exceeded by pre-boil SG by 5 points. My post boil volume was 0.5G more than recipe predicted. I can't imagine not boiling off that additional 0.5G would cost me 22 points on my post boil gravity. I checked the reading 3 times on 3 different samples.

    I ended up boiling 2# of DME in 1L water to bring the post boil kettle OG closer to the target gravity. Got it up to 1.062 where recipe target was 1.068. By entering this new OG in the brew log brewersfriend is reporting reasonable brewery efficiency.

    What do I need to change in either my recipe or profile to adjust for this huge miss in OG?

    How should I account for adding the DME during my brew session to correct for the OG during my brew session in the brew log and/or my recipe?

    This turned out to be my longest brew day ever at 10 hours thanks to having to boil and chill the DME after I'd already chilled my kettle.

    As a BIAB brewer I've been using the biabacus Excel spreadsheet from http://www.biabrewer.info. I wanted to do a Heady Topper and biabacus didn't support the number of hop entries needed where brewersfriend did. I had biabacus dialed in with my equipment. Now I need to figure out how to dial in brewersfriend.
     
  2. DonY

    DonY New Member

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    Re: I missed my OG by 22 points but exceeded by pre-boil gra

    After a nights rest from a long brew day and reviewing all the numbers I should have been suspect on what the recipe was reporting. It predicted my pre-boil gravity of 1.027 (I actually hit 1.032, so, close) with a post boil gravity of 1.068 (actual was 1.047 and way off target). I should have been suspicious that I would gain 21 points during the boil due to boil off and the late addition of Brun Leger sugar (PPG of 42 and making up only 7% of the fermentables in this recipe).
     
  3. Ozarks Mountain Brew

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    Re: I missed my OG by 22 points but exceeded by pre-boil gra

    remember to set your loss rates in your profile for different types of brew processes or sizes, I have one set for extract, 10 gallon, 20 gallon and 25 gallon, all are different and you have to put all sugars in the fermentable section not the other, also your yeast attenuation and the whole process efficiency will change the settings that you read for your target numbers so for best practice get each profile dialed in on a easy beer before you go gung ho on a triple ipa or barely wine or you will be off on your numbers, the default numbers you are seeing are an average based on all types of brewing
     
  4. DonY

    DonY New Member

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    Re: I missed my OG by 22 points but exceeded my pre-boil gra

    I already felt I had my equipment losses dialed in after 10+ BIAB brews using the BIABACUS Excel spreadsheet from biabrewer.info website. I entered my brew house efficiency, mash to kettle transfer loss, boil off rate, and kettle dead space (trub loss) I've measured doing 4 batches of another DIPA using same equipment in my equipment profile in Brewersfriend.

    The specific recipe in question in this thread has Brew Method = BIAB and Target = Fermentor predicting a boil gravity of 1.027 and an OG post boil of 1.068. That delta SG is where I'm baffled. Volume reduction due to boil off and adding 6% fermentables as sugar at end of boil doesn't account for that delta.

    My brew session measurement for the most part were spot on. Volume into kettle ended up 0.5G higher but with a 5 point higher SG. Boil off was as predicted as well.

    Brew session efficiencies were 86%,75%, 77% and 42% (not including the 2# of DME TO 1L of water to boost OG). If I account for the 1L water and DME BHE jumps to 58%.

    I experimented with the recipe since missing my OG so much and changed Target = Kettle and increased batch size by 1G to account for trub loss I'd set my kettle dead space for in my equipment profile. Low and behold when I did this the predicted OG was exactly what I measured during brew session!

    Something must be wonky with calculations for OG when Target = Fermentor and Brew method = BIAB.

    It would be helpful to know what brew house efficiency equation is used when brew method is BIAB and target is fermentor so I can ensure my equipment profile has all the correct parameters entered (values are entered based on my previous brews). When one has to add 25% of fermentables as DME and water to correct OG post boil I risk changing the target beer style which I fear I've done with this HT clone.
     
  5. DonY

    DonY New Member

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    Re: I missed my OG by 22 points but exceeded my pre-boil gra

    See my post in the Recipe Editor forum on behavior I've now discovered with Batch Type and Batch Volume fields: viewtopic.php?f=5&t=1820#p11511
     
  6. McKnuckle

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    Re: I missed my OG by 22 points but exceeded my pre-boil gra

    Hi Don,

    Nothing much to add, just wanted you to know that somebody is reading about your travails. I find eliminating the volume lost in the kettle during transfer to the fermenter to be simpler and more accurate. So I use ending kettle efficiency to gauge recipes instead of brewhouse. Hope the software is starting to grow on you!
     
  7. DonY

    DonY New Member

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    Re: I missed my OG by 22 points but exceeded my pre-boil gra

    I appreciate the feedback and that someone is reading my self discovery in this thread. I'm still concerned with the behavior of the predicted OG and how the uninitiated would design a new recipe with realistic targets. If I forget trying to target a recipe based on desired fermentor volume and instead target post boil volume (target = kettle) then I should enter my kettle efficiency in the Efficiency field. Not if I want realistic OG predictions. My kettle efficiency as measured for this brew session by brewersfriend was 77%! Entering that value in the recipe editor gives a predicted OG of 1.060 which is still much higher than the actual post boil OG of 1.047. Brewersfriend measured my fermentor efficiency at a 42%. In comparison all my previous BIAB brews have had a measured efficiency into kettle of approx 75% (brewersfriend measured 77% so pretty close) and efficiency into fermentor of approx 60% (brewersfriend measured 42% so not in agreement).

    To get the recipe editor to predict an OG that matches my actuals I have to enter a batch size volume of my post boil kettle volume and use an efficiency of 60% (my historical eff into fermentor for many BIAB batches as measured by another application) , not the brewersfriend brew session efficiencies of 77% (kettle) or 42% (fermentor). So, for future recipes in Brewersfriend it appears I should target my kettle volume but use the historical EIF I know from another BIAB Excel spreadsheet.

    By the way, I do like the Brew Session checklist and timers, not to be all gloom and doom :)
     
  8. Ozarks Mountain Brew

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    Re: I missed my OG by 22 points but exceeded my pre-boil gra

    is it only using the bib drop down or also all grain, I guessing when this website was created bib was just going main stream and hadn't been perfected and most people reported a lower efficiency with it, so that may be the case, try doing the same thing with all grain, thats what I use on my recipe's but I have a bib type of system and it works great, I do know that the yeast makes a difference as well as the attenuation of that yeast on the final ending gravity so play around with that also

    more often than not I get a lower ending gravity than this site reads but looking up the possible attenuation of the yeast Im using, I change it to the high side and it matches most of my brews
     
  9. DonY

    DonY New Member

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    Re: I missed my OG by 22 points but exceeded my pre-boil gra

    Setting method to All Grain drops the OG only 3 points for batch type = fermentor, but still way off from my actual OG.

    At this point it appears for me to get accurate prediction of OG with the recipe editor use batch type of "kettle", batch size of post boil volume but use efficiency into the fermentor which for me has historically been around 60% and not the kettle efficiency which is typically upper 60s to low 70s for me.
     
  10. Ozarks Mountain Brew

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    Re: I missed my OG by 22 points but exceeded my pre-boil gra

    I'm guessing since going from another system, the same goes for beersmith or any other software that not everything is going to match up so staying with one system would be the best way to go. trying to set you system to match your spread sheet might not be the best alternative than to just adjust to a new recipe here.

    the only thing I get messed up with on OG is too much water in the kettle and not boiling it off correct and 60% is kind of low, like I mentioned before just add a couple of pounds more of fermentable base grains might do the trick and adjust your recipes to achieve 70%, its going to be a better beer anyway lol

    also make sure your reading your hydrometer at 60
     
  11. DonY

    DonY New Member

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    Re: I missed my OG by 22 points but exceeded my pre-boil gra

    Except I've taken my actual batch measurements from the recipe's brew session tracked in brewersfriend and plugged those numbers back into the recipe editor and it still predicts the OG much higher than actual which means I'll always have a grist bill that's to light for the actual OG I want for future recipe. If I use my post boil kettle volume for batch size and brew house efficiency (efficiency into fermentor) it predicts the OG closer to what I actually measured.

    Thanks for engaging with me in this thread :).
     

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