The math and my hydrometer are not agreeing - Home Brew Forums

 Home Brew Forums > The math and my hydrometer are not agreeing

12-13-2011, 10:24 PM   #1
Daze

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Dec 2011
Kalispell, MT
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I just started a batch of Pomegranate wine. The Juice I used said clearly on the label that 8 fluid oz had 31 grams of sugar that means that one fluid ounce would have 3.875 grams of sugar in it. I put 120 fluid OZ of Pomegranate juice and 8 oz of water in a 1 gallon Jug. based on 3.875 grams of sugar in 1 fluid ounce of the POM there should be a total of 465 grams of sugar in my 1 gallon of juice and 8 oz of water. that would be just a little over a Lb of sugar in my 1 gallon batch. (actual total 1 Lb and .4 oz). The charts I have say that 1 Lb of sugar in 1 gallon of water will produce an SG of about 1.040 with a PA of about 5% but when I took a reading of the actual juice I got a reading of 1.052 or a PA of 7% Am I doing something wrong or is there something else I am missing???

12-14-2011, 12:09 AM   #2
david_42

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Oct 2005
Oak Grove, Oregon, USA
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Did you adjust for temperature?
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12-14-2011, 12:25 AM   #3
Daze

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Dec 2011
Kalispell, MT
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I did but it only changed things about about .002 of an SG

12-14-2011, 12:30 AM   #4
Golddiggie

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Dec 2010
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I get an OG of about 1.046 for that solution. Not that far off from what you actually got. Keep in mind, there could be things other than sugar giving you a higher reading than expected. Could be another case where using a refractometer would be a much better way to measure.
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On Tap: Caramel Ale, Mocha Porter II, MO SMaSH IPA
Waiting/Carbonating: 12.5% Wee Honey II, 8.9% Old Ale, English Brown Ale, Lickah ESB, Mocha Porter II
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12-14-2011, 12:36 AM   #5
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Jun 2008
Fayetteville, NC
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The SG measures all compounds and particles in the solution, not just sugar. Anything but water.

12-14-2011, 01:01 AM   #6
Daze

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Dec 2011
Kalispell, MT
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Quote:
 Originally Posted by Golddiggie I get an OG of about 1.046 for that solution. Not that far off from what you actually got. Keep in mind, there could be things other than sugar giving you a higher reading than expected. Could be another case where using a refractometer would be a much better way to measure.

Quote:
 Originally Posted by DoctorCAD The SG measures all compounds and particles in the solution, not just sugar. Anything but water.
So what you guys are saying is trust the math and not the hygrometer?? If so it looks like I need to add 1 cup of sugar to get the 7% ABV I am looking for.

12-14-2011, 01:02 AM   #7
Golddiggie

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Dec 2010
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99.95% sure that a refractometer will only measure the sugar in the solution in this case.

I used it on some apple juice (Mott's Natural) and got a gravity of 1.046 with no dilution. The cider I also measured came out to 1.044. I just checked the apple juice bottle... 27 grams sugar in an 8oz serving...

I would trust accurate measurements over the math. You never REALLY know what the gravity is unless you check. The math could be correct, but it needs to be verified. Especially since there could be variances on the sugar level that they don't change the label to reflect (the +/- or 'fudge' factor)...
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Hopping Tango Brewery

On Tap: Caramel Ale, Mocha Porter II, MO SMaSH IPA
Waiting/Carbonating: 12.5% Wee Honey II, 8.9% Old Ale, English Brown Ale, Lickah ESB, Mocha Porter II
Fermenting
K1:
K3: TripSix
On Deck: Caramel Ale
Mead [bottled]:Oaked Wildflower Traditional, Mocha Madness, Blackberry Melomel, maple wine

12-14-2011, 02:43 AM   #8
jdrum
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Jul 2011
vance, al
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the last batch of apple wine i made from bottled juice (all 10 bottles same brand 2 different batches) varied from 1.042 to 1.048, labeles can be deciving go with the readings.

jim

12-14-2011, 08:57 PM   #9
hbtasdfg
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Dec 2011
seattle, wa
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My guess is the label is just not accurate and your gallon is just out of spec but if you bought 10 gallons from 10 different lots and checked them all and averaged them it would be within a few percent of what the label says.

12-15-2011, 07:25 PM   #10
gregbathurst
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Apr 2009
Australia
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If you don't use a good quality hydrometer it is quite possible for the hydrometer to be incorrect. My first hydrometer was hopelessly inaccurate, I now use a professional quality one. Try testing your hydrometer against another one.