Author Topic: Inconsistent gravity readings.  (Read 1495 times)

Offline Tommy C

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Inconsistent gravity readings.
« on: May 23, 2011, 05:15:53 PM »
So the past 2 beers I have have made my OG gravity has been off by as much as .20 of what it's supposed to be and I am wondering why.  I have followed the recipes exactly and have double checked the anticipated measurements with brewtarget software. 

I have checked my hydrometer and it is calibrated properly.  My current theory is that both of these batches I have used my new 6.5 gallon carboy as a fermenter, after I top off my wort to bring it to a full 5 gallons I then pull a sample out to test the starting gravity.  I'm thinking that the tool I use to pull some of the wort out of the carboy is not getting deep enough down into the carboy, past the water I have just added(I do shake the carboy to mix it up but I don't do the best job at that because it's so heavy and awkward). 
Could this be the reason for my off readings?

Lastly, my final gravity each time has reached where it was supposed to, it's just the original gravity that is so off.  Any help and lessons in gravity would be appreciated.

Thanks! 

 

Offline hokerer

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Re: Inconsistent gravity readings.
« Reply #1 on: May 23, 2011, 05:28:49 PM »
How are you adding the topoff water?  Is there a way you can add it such that it mixes into the wort better?  Could you try adding some of the water, then the wort, and then whatever additional water you need to reach your volume?   Maybe use a racking cane into the carboy to "stir" the wort?
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Offline tygo

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Re: Inconsistent gravity readings.
« Reply #2 on: May 23, 2011, 05:35:34 PM »
It's probably that the wort and water are not mixed well enough.  Next time, just to see, take a reading on the wort before you add the water and accurately measure the volume of both the wort and water going into the carboy.  Then mix it up as best you can and take a gravity reading on the whole thing.  You'll be able to calculate what the gravity should be and compare that to what the hydrometer is telling you.  If there's a difference then that confirms that it's not mixed up well enough.
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Offline thomasbarnes

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Re: Inconsistent gravity readings.
« Reply #3 on: May 23, 2011, 06:00:46 PM »
So the past 2 beers I have have made my OG gravity has been off by as much as .20 of what it's supposed to be and I am wondering why.  I have followed the recipes exactly and have double checked the anticipated measurements with brewtarget software. 

Stir your wort thoroughly before you take your OG reading. It's very easy to get a density gradient* in your fermentor, especially if you add water. Also, make sure that you get a clear wort sample, a test glass full of hop particles and other trub will also throw off your readings.

* Density gradient, like oil floating on water, or what you see in a properly made black and tan cocktail.

Offline tschmidlin

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Re: Inconsistent gravity readings.
« Reply #4 on: May 23, 2011, 08:59:32 PM »
Personally, I would calculate the SG and go with that.  If it's an extract batch, the OG will be pretty close to whatever you calculate, even using steeping grains.
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Offline weazletoe

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Re: Inconsistent gravity readings.
« Reply #5 on: May 23, 2011, 09:06:15 PM »
Yup, like said, you gotta mix the crap outta your wort / top off water. No worries though, even if your hydrometer tells you different, as long as your volume is correct, your OG is pretty much foolproof.
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Offline Tommy C

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Re: Inconsistent gravity readings.
« Reply #6 on: May 24, 2011, 03:45:46 PM »
Cool.  Thanks for all the info, lesson learned, stir the hell out of it!

Offline thomasbarnes

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Re: Inconsistent gravity readings.
« Reply #7 on: May 25, 2011, 02:40:46 AM »
Cool.  Thanks for all the info, lesson learned, stir the hell out of it!

The simple way to get a good gravity reading is to take it after you've aerated your wort, assuming you're oxygenating your brew by rocking or stirring your fermentor.

Offline a10t2

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Re: Inconsistent gravity readings.
« Reply #8 on: May 25, 2011, 08:30:13 AM »
The simple way to get a good gravity reading is to take it after you've aerated your wort, assuming you're oxygenating your brew by rocking or stirring your fermentor.

If you're brewing with extract, I think the simplest way is just to calculate it and not worry about taking a reading at all.
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Re: Inconsistent gravity readings.
« Reply #9 on: May 25, 2011, 08:42:03 AM »
Personally, I would calculate the SG and go with that.  If it's an extract batch, the OG will be pretty close to whatever you calculate, even using steeping grains.

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Re: Inconsistent gravity readings.
« Reply #10 on: May 25, 2011, 10:11:35 AM »
Make sure it's mixed well. You can easily get layering and throw off your readings.