How can my preboil gravity be off, but my OG on?

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chefchris

chefchris

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My preboil gravity was suppose to be 1.060, I got 1.052. FG was suppose to be 1.065, I got 1.064 (not exactly on but close enough). I know the two figures are directly correlated, so how did I still 'hit' my OG when my pre boil gravity was that far off? I have no doubt in my mind that I hit all my volumes. I bought a sight glass from Bobby_M and it has helped tremendously.
 
Your preboil was off .002 and the post boil was off .001. That's close, and it may simply be that you had an ounce or two more of water. Or, maybe your efficiency is .1% different that you planned. It's really a minute difference.
 
YooperBrew said:
Your preboil was off .002 and the post boil was off .001. That's close, and it may simply be that you had an ounce or two more of water. Or, maybe your efficiency is .1% different that you planned. It's really a minute difference.
Click to expand...

Whoops, sorry. My pre boil was 1.052.
 
Some of the more experienced guys can correct me if I am wrong but I was just reading the "designing a great beer" book and it stated that the post boil gravity will always be higher than pre-boil due to boiling off water. Effectively you are concentrating the wort so it gets "stronger" the more you boil.
 
This will not be terribly helpful but either (a) your expected pre-boil and post-boil gravities/volumes were calculated incorrectly, or (b) one of your gravity or volume measurements is off.

What were your expected (EDIT: and actual) pre- and post-boil volumes?
 
FlyingHorse said:
This will not be terribly helpful but either (a) your expected pre-boil and post-boil gravities/volumes were calculated incorrectly, or (b) one of your gravity or volume measurements is off.

What were your expected (EDIT: and actual) pre- and post-boil volumes?
Click to expand...

Estimated Pre Boil Volume: 7 gallons @ 1.060
Actual Pre Boil Volume: 7 gallons @ 1.052

Estimated Post Boil Volume: 5.5 gallons @ 1.065
Actual Post Boil Volume: 5.5 @ 1.064

budbo said:
Then one of your readings was off. If your OG is good be happy :)
Click to expand...

Yeah, I am happy with it, just curious as to why this happened.
 
Expected: 7 * 60 / 5.5 = 76, or a 1.076 SG

Actual: 7 * 52 / 5.5 = 66, or a 1.066 SG

So your measurements are off a little (1.064 vs 1.066, who cares), and something in the calcs is off a lot (1.076 vs 1.065)
 
FlyingHorse said:
Expected: 7 * 60 / 5.5 = 76, or a 1.076 SG

Actual: 7 * 52 / 5.5 = 66, or a 1.066 SG

So your measurements are off a little (1.064 vs 1.066, who cares), and something in the calcs is off a lot (1.076 vs 1.065)
Click to expand...

Interesting. Thanks, I wasn't worried, like I said, just curious.
 
Assuming that you didn't add any fermentables during the boil, the most likely explanation is you didn't stir the pre-boil wort enough to thoroughly mix the heavy first runnings with the lighter subsequent runnings

.-a.
 
ajf said:
Assuming that you didn't add any fermentables during the boil, the most likely explanation is you didn't stir the pre-boil wort enough to thoroughly mix the heavy first runnings with the lighter subsequent runnings

.-a.
Click to expand...

I did make sure I swirled it pretty good to get a homogeneous sample.
 
I think we are all going through the same thought process trying to figure this out. First thing I wanted to say was that you boiled off too much volume, but then I noticed you said you hit your mark. Then only thing I could think would be that your readings were wrong, or maybe not adjusted for temperature. Though I think you have said above that you are confident with your gravity measurements. When I read ajf's post I thought that had to be it, but you say you swirled it pretty good which is really the same as what I do and everything goes pretty routine for me.

I think we all may just be stumped here. There doesn't seem to be a logical explaination as to why this would happen. Another mystery only known by the beer gods it would seem. At 1.064 I bet it won't take much of this beer to get a good buzz going, let us know the FG and how it turns out!

Also, I just moved to Ocala, got a few beers goin since I have been here but I was wondering if you had any info on the water profile down here? Also is there a HBS up there in Gainesville or do you just buy online like me?
 
patrck17 said:
I think we are all going through the same thought process trying to figure this out. First thing I wanted to say was that you boiled off too much volume, but then I noticed you said you hit your mark. Then only thing I could think would be that your readings were wrong, or maybe not adjusted for temperature. Though I think you have said above that you are confident with your gravity measurements. When I read ajf's post I thought that had to be it, but you say you swirled it pretty good which is really the same as what I do and everything goes pretty routine for me.

I think we all may just be stumped here. There doesn't seem to be a logical explaination as to why this would happen. Another mystery only known by the beer gods it would seem. At 1.064 I bet it won't take much of this beer to get a good buzz going, let us know the FG and how it turns out!

Also, I just moved to Ocala, got a few beers goin since I have been here but I was wondering if you had any info on the water profile down here? Also is there a HBS up there in Gainesville or do you just buy online like me?
Click to expand...

Yeah, I'm stumped as well. Oh well.

Yes, there is a LHBS here called Hogtown Ale Works. I'm fixing to start working there in the next month or two. I teach all grain classes there every few months and we're starting a homebrew club in conjunction with them. Great guys. So I usually buy my stuff there, the only complaint I have is their yeast selection. They don't have much of a choice as far as liquid yeast, and if they do have it, it's usually a year past it's expiration date. Though I did just pick up some California V for this beer that expired in April, so that wasn't too bad. I've been forced to use dry yeast for the majority of my beers. Other than that, no complaints. Good prices and helpful staff.
 

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