Weird OG readings with topped-off extract wort

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JstnMoyer

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Has anyone come across this weird OG issue with topped-off partial boil wort?

Just brewed my second partial boil extract batch yesterday. I chilled my concentrated wort and added to glass carboy (2.5 gallons) and topped it off with water getting it to 5 gallons. I aerated more by shaking/rocking carboy then took a gravity reading off the top with a beer thief. My calculations should have gotten me an OG of about 1.060 but it was 1.034. This happened in my first batch when I was expecting 1.067 and got 1.036. but that beer feels like somewhere between 6.5% and 7% abv when drinking it (it's quite delish).

My theory is that the OG is off because the concentrated wort has not fully mixed with the top-off water. I suppose I COULD have sat there and shook the hell out of it more. I also noticed a lot of cold break in there. I am just a day into ferm now with no bubbling but I don't want to open up the carboy just to take a better OG... unless someone can convince me otherwise.
 

STMF

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Has anyone come across this weird OG issue with topped-off partial boil wort?

My theory is that the OG is off because the concentrated wort has not fully mixed with the top-off water.
Agree. Extract batches are usually right on the money for OG.
 

Qhrumphf

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My theory is that the OG is off because the concentrated wort has not fully mixed with the top-off water.
This is 99% likely explanation. If you grab more water than wort, reading will seem low. If you grab more wort than water, reading will seem high.

With topped off extract batches, as long as the right fermentables are added to the right finished volume, gravity should be correct to recipe.

Alternatively, since adding water is just diluting, you can read the concentrated wort and then calculate the gravity after topping off. But small errors (volume namely) can throw the calculation off, so precise accurate measurement is key.
 

ncbrewer

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I stopped taking OG readings on extract batches years ago. You can stir and take samples until the reading matches what it should be, but you gain nothing except the possibly contaminating the wort (IMO less handling is better).
 
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JstnMoyer

JstnMoyer

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That might explain why my first partial boil recipe kit instructions from Northern Brewer didn't include instructions for taking any gravity readings. I was mad they didn't include it but now I know it's not necessary.

Speaking of those instructions, it also didn't include any steps for aeration. I was concerned after reading about aeration techniques that the instructions let me down and that I didn't get enough oxygen in there for the yeast. I just hoped that pouring top-off water on the chilled wort was sufficient. Well, the beer turned out great. The instructions were fine as simple as they are :)
 

RM-MN

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That might explain why my first partial boil recipe kit instructions from Northern Brewer didn't include instructions for taking any gravity readings. I was mad they didn't include it but now I know it's not necessary.

Speaking of those instructions, it also didn't include any steps for aeration. I was concerned after reading about aeration techniques that the instructions let me down and that I didn't get enough oxygen in there for the yeast. I just hoped that pouring top-off water on the chilled wort was sufficient. Well, the beer turned out great. The instructions were fine as simple as they are :)
The kit probably included dry yeast which doesn't need aeration. Congrats on making a great beer. May you make many more.
 

Dgallo

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That might explain why my first partial boil recipe kit instructions from Northern Brewer didn't include instructions for taking any gravity readings. I was mad they didn't include it but now I know it's not necessary.

Speaking of those instructions, it also didn't include any steps for aeration. I was concerned after reading about aeration techniques that the instructions let me down and that I didn't get enough oxygen in there for the yeast. I just hoped that pouring top-off water on the chilled wort was sufficient. Well, the beer turned out great. The instructions were fine as simple as they are :)
I always had better luck with largemouth carboy or buckets when I was toppling off with extract brews. Was much easier to harmonize the wort and get an accurate reading
 
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davidabcd

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The bucket method (instead of carboy) does seem easier as far as even distribution is concerned. I pour my 2 or 2 1/2 gallons of top-off water from a decent height to give it momentum into the wort and then use a slotted steel spoon like an oar but straight down for thorough mixing. I've read (and was also pointed out) that with dry yeast, aeration isn't necessary. I still aerate though since doing it is not a negative for me.
 
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JstnMoyer

JstnMoyer

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The kit probably included dry yeast which doesn't need aeration.
Home brewing is a two-pronged hobby: brewing and internet scavenging. I've read How to Brew cover to cover and there are still things I pick up between each batch on the internet. Like this little nugget about dry yeast and aeration. And extract recipes OG being accurately predictable. The constant discovery makes it fun.

Learn, brew, rinse & repeat.
 

balrog

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You could always go the route of buying a 5 gallon bucket paint stirrer at the hardware store in order to really mix your extract, partial boil, topped off batches. But make sure you also go down the hardware store aisle where cleaning supplies are. And wall and cabinet sponges. Some ceiling cleaning supplies too.

Ask me how I know. I don't use the paint stirrer and drill anymore. It's a bit indelicate.
 
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