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Pre boil and OG efficiency differences

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pretzelb

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I'm hopeful that I'm on the right track for my efficiency problems being from my crush but one thing I noticed in my log is my numbers show the efficiency to go down from pre boil and starting. Looking at BeerSmith it looks like nearly all the numbers I captured show the efficiency into fermenter to be lower than the efficiency into boiler. Is that normal? What issue would that indicate? I assumed that it would remain the same or close to it after boil but in some cases I see a drop of 5 to 9%.
 

smizak

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Did you measure the volume in the kettle while it was near or at boiling? Water expands about 4% from boiling to room temp, I made the same mistake on my first AG. 7.5 gal in the kettle was really 7.2 gal so my efficiency calc was skewed accordingly.
 
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pretzelb

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Did you measure the volume in the kettle while it was near or at boiling? Water expands about 4% from boiling to room temp, I made the same mistake on my first AG. 7.5 gal in the kettle was really 7.2 gal so my efficiency calc was skewed accordingly.
No, I measure my volume in the kettle during sparge. It's how I know when to stop draining. I try to be as accurate as I can but I use a dip stick made of cpvc with lines drawn on it to measure and it may be a bit off. I have a line for 6.5 and BeerSmith is now configured to tell me 6.41g so I have to guess a bit when I'm close. But I do try hard to not go over the 6.5g line.

I have noticed a difference from in the kettle post boil to in the fermenter. I check after a normal 60 min boil and try to be around 5.25 to 5.5g but lately the amount my carboy shows is right at 5g and I typically dump all of it into the carboy. So my values into fermenter might be off. I need to recheck that.
 

Catt22

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Efficiency numbers are highly dependent on accurate volume measurment and proper accounting for all losses wherever they may occur. So, what I'm getting at is that when calculating the efficiency in the fermenter, you would take a gravity reading and a volume measurement. There are sure to be significant losses along the way to the fermenter. Some wort will be left behind in the mash tun, some will be absorbed by the hops and some may be lost to hoses or chillers. The best way to get a handle on the efficiency is to measure it pre-boil only. This eliminates the hop absorption issue and there is likely little sugar remaining in any wort left behind in the mash tun. You still need to get an accurate measurement on actual volume in the kettle, but otherwise it's fairly straightforward. As for the fermenter, you will want to take a starting gravity reading so you know how close you got to your target gravity, but I would not try to calculate my efficiency on those numbers. If you missed by much, just make adjustments next time accordingly.
 
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pretzelb

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Efficiency numbers are highly dependent on accurate volume measurment and proper accounting for all losses wherever they may occur. So, what I'm getting at is that when calculating the efficiency in the fermenter, you would take a gravity reading and a volume measurement. There are sure to be significant losses along the way to the fermenter. Some wort will be left behind in the mash tun, some will be absorbed by the hops and some may be lost to hoses or chillers. The best way to get a handle on the efficiency is to measure it pre-boil only. This eliminates the hop absorption issue and there is likely little sugar remaining in any wort left behind in the mash tun. You still need to get an accurate measurement on actual volume in the kettle, but otherwise it's fairly straightforward. As for the fermenter, you will want to take a starting gravity reading so you know how close you got to your target gravity, but I would not try to calculate my efficiency on those numbers. If you missed by much, just make adjustments next time accordingly.
That is a good point. My readings for volume after the boil aren't as accurate as they should be. At the end of the day my patience is usually low and I tend to rush at that stage. I also wonder if my post boil gravity readings are a bit skewed by hops and break material in the kettle. I do try to keep that stuff out for my refractometer but it isn't easy.

I think I'm looking at those fermenter efficiency numbers because BrewSmith calculates it for me. Since my efficiency numbers for pre boil are usually better I'd certainly rather use them.
 
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pretzelb

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For whatever reason my last batch showed different numbers. Into the boiler it was 70% and into the fermenter it was 74%. But my measurements into the fermenter aren't nearly accurate enough.
 

Catt22

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The cooled wort will shrink and the gravity will increase some as a result relative to the hot wort gravity. This could account for part of the discrepancy.
 
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pretzelb

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The cooled wort will shrink and the gravity will increase some as a result relative to the hot wort gravity. This could account for part of the discrepancy.
Interesting point. I think this time I took a sample while the wort was hot, not sure about last time. I will always cool the sample before taking a reading so that should be a constant. But I wonder if the reading would be different from my cooled sample from hot wort vs a sample from cooled wort. And if they are different the next question would be which is more accurate with respect to plugging into efficiency calculations and OG notation.
 

Catt22

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Interesting point. I think this time I took a sample while the wort was hot, not sure about last time. I will always cool the sample before taking a reading so that should be a constant. But I wonder if the reading would be different from my cooled sample from hot wort vs a sample from cooled wort. And if they are different the next question would be which is more accurate with respect to plugging into efficiency calculations and OG notation.
What I was really getting at was that the cooled wort will decrease in volume which you need to take into consideration when calculating efficiencies. Obviously, the sample should be cooled or a temperature correction applied when taking a gravity reading, but don't overlook the wort volume change. The volume is less for the cooler wort, but the total sugar content remains the same.
 
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pretzelb

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What I was really getting at was that the cooled wort will decrease in volume which you need to take into consideration when calculating efficiencies.
I think I understand now. My BetterBottle carboy has some marks for each gallon but they aren't very accurate and don't mark the .25 quantities like they should. It would be useful if I had everything from 4g to 6g marked by the 1/4 gallon to better estimate the in fermenter volume. Until I do that it's not going to be a good estimate of efficiency.

Thanks.
 

jagg

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I think I understand now. My BetterBottle carboy has some marks for each gallon but they aren't very accurate and don't mark the .25 quantities like they should. It would be useful if I had everything from 4g to 6g marked by the 1/4 gallon to better estimate the in fermenter volume. Until I do that it's not going to be a good estimate of efficiency.

Thanks.
That is correct, thats the only way to know for sure.:rockin:
 

Northcalais40

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Won't you also lose efficiency when you rack to the carboy and leave behind wet hops/trub? This is a necessary loss. When you measure volume and density pre-boil the trub material is in suspension and counts toward volume, and density maybe (it does sink right?). I always use leaf hops and leave alot of liquid behind (like a gallon of rehydrated hops or so). I dont squeeze the liquid out or anything I just let it run dry through my pick up tube and figure I've filtered out some junk I don't want in the carboy.

I only ever concern myself with overall efficiency (maybe it's rightly called brewhouse efficiency?) ie. OG/potential OG. I have been consistent enough to accurately predict my OG's, so whatever works.
 

kozydogg

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So I think I'm having a similar problem. I am getting about 92% efficiency and for my last batch, my pre-boil gravity of 7.5 gal was 1.046. My program said my predicted OG should be 1.081 and my actual target OG was 1.073.

However, after the boil, my OG was actually 1.066. What gives?
 

OLDBREW

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A lot of things change after the boil. depending on grain type, hop usage, evaporation rate, and gravity of the brew. Some grains give you tons of break materials, if you use more hops in a recipe, you will soak up more liquid, but the hops will go through into the fermenters giving you more volume less wort, plus shrinkage from heat changes volume.

the best way to figure out accurate efficiency is by weight, not volumes. Hard to do for the average homebrewer, so a guesstimate is as close as you will come.
 
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