specific gravity question

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specific gravity question

Postby herocomplex » Sun Aug 29, 2004 7:04 pm

Perhaps the resident experts can help me out here, because I'm really confused. I made the Propensity Pilsner from "The New Complete Joy of Homebrewing" EXACTLY to the recipe. I used three gallons of regular tap water and two gallons of distilled water for softening.

I came out with an original specific gravity around 1.065! That seems crazy to me. There's must not much in that thing, how can it be so high? I even added another gallon of water to try to drop it some, but it was still high. I tranfer my beer midway through the brewing, but I wonder if I need to filter it better when I put it into the primary.

Any ideas on the crazy high readings I get?

Thanks all, I get so many great ideas from here.

- Sage
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Postby just-cj » Mon Aug 30, 2004 5:50 am

Are you sure that your top up water was mixed well with your wort? That's often a problem when extract brews give you too high or too low gravity readings.
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mixing

Postby herocomplex » Mon Aug 30, 2004 10:34 am

Well, I shook it around pretty good in the carboy. How much shaking is required to get a good mixing? Would this alone explain the high readings?
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Honey is an odd barrel of worms

Postby Dr Strangebrew » Mon Aug 30, 2004 4:21 pm

The sugar content of honey will vary both within the batch of honey and from batch to batch (of honey). Thus, so will the gravity reading of any beer containing honey. It is very hard to predict what gravity contribution honey will give. Don't worry about it. It is true that Papazian lists 1.048-1.052 as PREDICTED starting gravities, but he didn't reveal how he calculated those values. I typically disregard predicted original values of recipes if the author doesn't at least state the brand of malt extract used, or from what company the grain was from (in an all-grain beer).

Which brings me to another point. Papazian doesn't list the company that made the malt extract. Gravity contribution, and fermentability by the way, varies across different malt extract companies. These differences in extract potential I suspect would be small compared to the varying sugar content of honey, but they may have contributed a few of the gravity points.

Let's use as an example, a batch I made. Right now I have a honey wheat beer conditioning in a carboy. I used 3.5 lbs each of pale ale and wheat malt. I used 2.25 lbs of honey. I had an O.G. of 1.048! This is what Papazian claims is a reasonable SG for his recipe. He used 5 lbs of extract. Common convention for converting extract wieght to equivalent grain weight is

extract weight times 3 divide by 2 equals equivalent grain weight

This gives an equivalent grain weight of 7.5 pounds. He also used 1 lb of crystal malt, so the total equivalent grain weight would be 8.5 pounds- this is a ROUGH estimate. I used a pound and a half less then what was needed and got the same OG as predicted by the recipe.

Bottom line: Don't worry, relax, have a homebrew. Sugar content in honey varies.

As a side note, I make honey beer every now and again. When I use a substantial portion of honey, greater than one pound, I typically use a yeast strain that is very alcohol tolerant. This way I am sure to get a fully fermented beer. If you didn't use, or are not sure if you did use, a yeast with high alcohol tolerence, don't worry it is not the end of the world. In fact, my last beer, a honey wheat, I didn't consider alcohol tolerence and the beer fermented down to 1.007. More than likely you are fine.

Cheers,
Nate
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thanks!

Postby herocomplex » Mon Aug 30, 2004 5:25 pm

That makes a lot more sense. I think his recipe is simply high on the malt. I'll definitely start taking predicted starting O.G. with a huge grain of salt. Thanks for the great info.
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One last thought...

Postby Push Eject » Tue Sep 14, 2004 7:01 pm

Final, perhaps unnecessary thought; check your hydrometer... I once tossed one that was way off.

It should read 1.000 in water at 59 degrees.

Cheers,
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A word about hydrometers.

Postby jeff » Wed Sep 15, 2004 10:27 pm

Though I doubt the hydrometer is to blame in this case, the specific gravity or density of water does vary with temperature. Hydrometers are thus calibrated at specific temperatures. Those used for brewing use are most commonly calibrated at 60 F (15.6 C) or 68 F (20 C). This means that the reading must be performed at the calibration temperature or a correction equation has to be used to find the real density. The Final Analysis tool at BeerTools.com allows for temperature correction if the temperature of the wort is measured at the time of the reading.

In my experience, the most common reason for errors in original gravity when brewing extract based beers is innaccurate measurement of volume after the evaporative effects of boiling. When brewing all-grain type recipes, original gravity can be affected by a host of other factors including mash pH and grind quality.

If anything, I personally prefer a higher gravity than expected than one that is too low. :wink:
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Re: A word about hydrometers.

Postby Push Eject » Thu Sep 16, 2004 1:06 am

jeff wrote:If anything, I personally prefer a higher gravity than expected than one that is too low. :wink:

Yeah, but that's just because you're a lush.

Charlie :mrgreen:
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