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 Home Brew Forums > cocoa powder's affect on final gravity

10-15-2012, 01:57 PM   #11
JLem
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Quote:
 Originally Posted by nickmv Gravity is a measure of the density of the liquid in comparison to water (1.00). Density is a measure of mass divided by volume. If you have cocoa powder mixed in, chances are your volume may have changed a tiny bit, but not much. Mass, on the other hand, may have changed a decent amount. I'm not gonna do any research into it, but I wouldn't just discount it. However, it could be that both mass and volume increase in correct proportions for it not to matter. Food for thought....
The hydrometer measures the density of the liquid. If something is dissolved in it (like sugar) the mass will increase but there will be little volume increase, so the density will be higher (more mass per volume). However, if something is suspended in the liquid and not dissolved (like cocoa powder) neither the mass nor the volume of the liquid changes, so density is unaffected. As an extreme example...the density of water does not change when you add a handful of sand to it.

10-26-2012, 01:25 AM   #12
apshaffer
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I pitched a pack of US-05 (what I had) two weeks ago. I just racked to my keg and the gravity measured 1.024. It a little higher than I expected, but it is what it is.

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10-26-2012, 03:50 AM   #13
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1. Just assume cocoa was sugar... Plug into beersmith or calc by hand and it would add what, 1-2 points? So not being sugar, cocoa will add less than that.

2. A FG of 1.024 sounds like lousy attenuation. Calculate it and see what safe ale says its supposed to be. 75% would put you at 1.016. I Fear your beer will be rather sweet.

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10-26-2012, 04:45 AM   #14
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Quote:
 Originally Posted by JLem As an extreme example...the density of water does not change when you add a handful of sand to it.
And (for the purposes of this thread) cocoa powder = sand. It falls out of suspension pretty quickly in my experience.
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10-26-2012, 01:55 PM   #15
JLem
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Quote:
 Originally Posted by dwarven_stout And (for the purposes of this thread) cocoa powder = sand. It falls out of suspension pretty quickly in my experience.
precisely

10-26-2012, 03:45 PM   #16
Homercidal
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Are you using a refractometer to measure the FG by chance?

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10-26-2012, 03:48 PM   #17
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Agreed. If so, a refractometer can't be used to measure gravity of fermented beer.

I pitched a 1.5L starter in mine, and after 7 days, it was at 1.011, so pretty much done (target is 1.010). Measured with hydrometer, and the cocoa powder didnt cause any measurement issues. Most of it is on the bottom of the carboy anyways.

That being said, I tasted the beer (this recipe) when I took a reading, and it was sweet and kinda boozy, and nowhere near ready. Definitely needs a good month and a half rest. I'm expecting it'll be awesome when I serve at Thanksgiving.

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10-26-2012, 06:41 PM   #18
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I use a hydrometer, and I agree it's lousy attenuation. The question is why the lousy attenuation. I thought maybe it had something to do with the cocoa powder, but apparently not. At least not to the degree I experienced.

In my 5 years of brewing all grain, I have never had an attenuation issue. If anything, my beers finish drier than beersmith predicts. Not sure why it happened this time. Ambient temps were fairly constant (60's), mash temp was 152ish. I used 2 pack of yeast pitched a few weeks apart, and it spent 5+ weeks in the fermenter. It should be finished. It went from 1.064 to 1.024. I agree it should have finished about 10 points lower, but it didn't. I'm not pitching any more yeast. It in the keg now, and I'm moving on.

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