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-   -   Advice Needed for Hitting Gravity (http://www.homebrewtalk.com/f13/advice-needed-hitting-gravity-347586/)

PistolaPete 08-14-2012 04:19 PM

Advice Needed for Hitting Gravity
 
I usually brew extract w/ grains or partial mash and use the Hopville calculator to estimate my OG for 5.5 gal batches. I start testing the OG after I fill the fermenter up to 5.25 gallons and dilute more if my the OG is still too high. I've been pulling out samples to read the OG since the bubbles in the fermenter seem to to be attracted to my hydrometer and make it hard to read. I dump the samples to avoid infection and if I do this 3-4 times I am dumping around 24-36oz of beer just to try and hit my target OG.

1) Is there a better way to hit your target OG than what I'm doing? Maybe one that doesn't waste as much beer?

2) This is a seperate but related question: How much variation in OG does it take to be noticed? (I would guess it has to at least go from 1.050 to 1.055 to even notice any flavor or mouthfeel differences but please correct me if I am wrong!)

billl 08-14-2012 05:28 PM

If you are doing extract batches, you will hit your gravity if you have the right amount of water. All the big manufactures create extract that is incredibly reliable and consistent. If you are "missing" your OG, then it is a measurement problem. The usual cause is that topoff water not mixing with the wort.

How much is noticable is really dependent on who is noticing. I can't tell a 6% vs 6.2%, but maybe someone else can. I certainly wouldn't be dumping precious beer just to hit an OG number!

Qhrumphf 08-14-2012 05:45 PM

Quote:

Originally Posted by billl
If you are doing extract batches, you will hit your gravity if you have the right amount of water. All the big manufactures create extract that is incredibly reliable and consistent. If you are "missing" your OG, then it is a measurement problem. The usual cause is that topoff water not mixing with the wort.

How much is noticable is really dependent on who is noticing. I can't tell a 6% vs 6.2%, but maybe someone else can. I certainly wouldn't be dumping precious beer just to hit an OG number!

+1. You're probably just not mixing thoroughly enough.

I'd also suggest pulling gravity before topping off. It uses the same math as AG brewers use when taking preboil gravity. With gravity in shortened form, (SG1)(V1)=(SG2)(V2). Say after your boil, you have 3 gallons of wort and it reads 1.070, (70)(3)=210. If you want 5 gallons, you'd divide by 5 and get 42, meaning if you top of to 5 gallons your OG would be 1.042. Alternatively, if you want an OG of 1.055 you divide by 55 and see you'd need to top of to 3.81 gallons.

PistolaPete 08-14-2012 06:01 PM

Quote:

Originally Posted by billl (Post 4330056)
If you are doing extract batches, you will hit your gravity if you have the right amount of water. All the big manufactures create extract that is incredibly reliable and consistent. If you are "missing" your OG, then it is a measurement problem. The usual cause is that topoff water not mixing with the wort.

How much is noticable is really dependent on who is noticing. I can't tell a 6% vs 6.2%, but maybe someone else can. I certainly wouldn't be dumping precious beer just to hit an OG number!

I know, it hurts to dump the samples! Like I said before, I am brewing w/ extract plus grains or partial mashes so those grains have an effect on gravity and I'm sure efficiency is playing a role when you start adding grains to the equation especially w/ the partial mashes. On one of my recent recipes I put into the Hopville calculator gave me a range of 1.044-1.051 with an estimated OG of 1.049. I am usually well within the estimated range it gives me, usually within 0.005 points. I guess the real question is at how much does the gravity need to increase/decrease before there a noticable difference in the end taste of the beer? (So I can avoid tossing samples if I am trying to be too precise about it.)

billl 08-14-2012 06:38 PM

You are being way to "precise" about it. If you are consistently hitting within a couple points of the recipe OG, that means you are right on target.

As for taste thresholds, that varies from person to person. It also really varies from style to style and at various ABV levels. eg a 0.5% drop in ABV on a 12% imperial stout is different than the same drop in a 4% mild.

Qhrumphf 08-14-2012 08:20 PM

Quote:

Originally Posted by billl (Post 4330260)
You are being way to "precise" about it. If you are consistently hitting within a couple points of the recipe OG, that means you are right on target.

As for taste thresholds, that varies from person to person. It also really varies from style to style and at various ABV levels. eg a 0.5% drop in ABV on a 12% imperial stout is different than the same drop in a 4% mild.

I don't think there's anything wrong with attempting to fine tune process to get numbers as consistent as possible and keep recipes repeateable. That said, if I'm going to be within a point or two of the OG that I want, I leave it. If it's off by more than that, I usually correct it.

The second part I agree with. The way I see it, the stronger the flavor, the more wiggle room there is. Barleywines, Imperial IPAs, etc, I wouldn't see much difference. Session beers, subtly flavored beers, anything where it's walking a very fine balance or where it's hard to hide flaws, a couple points could be an issue. It's not just the body and alcohol, but the bitterness can be affected as well.

PistolaPete 08-14-2012 09:49 PM

Most of the brews I have been doing lately are usually between 1.048 and 1.058. So maybe a variation of .002 may not be that bad for these types of OGs, but it sounds like a variation on .005 would be a cause for concern?

(and I gently stir with a spoon or paddle when topping off w/ water so the solution is thoroughly mixed up for an accurate grav reading)

Qhrumphf 08-14-2012 10:55 PM

.005 is more than I like, but from what I've seen from a number of folks on here, they're fine with that much variation. I'm probably just anal about it.

The problem with taking a reading after topping off is wort is a lot denser than water, and it's tough to mix them. Boiling homogenizes them, and fermentation homogenizes them, but otherwise you'll almost never get an accurate reading. I've taken the entire batch in the fermenter, shaken it until my arms were about to fall off, and it still wasn't thoroughly mixed. Whenever anyone says they've shaken or stirred enough to get an accurate reading (myself included), I'm not convinced. A gentle stir isn't enough, I can guarantee that.

That's why I started doing it the way I suggested above (and the math is really really easy)- the gravity of your wort before top-off will be accurate, and then it's just scaling it. There's a finite amount of sugars (and whatever else) dissolved in the wort (speaking in terms of mass, not gravity) that doesn't change with the volume. So the gravity at one volume is directly related to the gravity at another volume. And it's certainly a lot easier, safer, and less messy than "top-off, pull sample, top-off, pull sample", not to mention wasting less wort. Only one sample needed, zero guesswork or margin for error.

Qhrumphf 08-14-2012 11:06 PM

(Also, since it's relevant to the whole topic) I pulled the technique from the chapter on hitting target gravity from Ray Daniels' "Designing Great Beers". If you've got a copy, read that chapter. If you don't, I highly recommend the book.

PistolaPete 08-15-2012 02:23 AM

Quote:

Originally Posted by Qhrumphf (Post 4331062)
(Also, since it's relevant to the whole topic) I pulled the technique from the chapter on hitting target gravity from Ray Daniels' "Designing Great Beers". If you've got a copy, read that chapter. If you don't, I highly recommend the book.

I don't have that book, but maybe it will be my next purchase since I've heard many good things about it. I wasn't aware of the fact that the two solutions have problems mixing. I will take that into consideration from now. I am usually pretty close to what my Hopville says I should be, but it never hurts to try and perfect one's methods. So with the method you mentioned above, does it matter if I check the gravity after it has cooled in the icebath and BEFORE I pour it off the trub or AFTER I pour it off the trub?


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