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Recipes that state Original Gravity - is that Pre Boil?

 
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TTodd



Joined: 11 May 2013
Posts: 21



PostLink    Posted: Thu Apr 03, 2014 11:31 pm    Post subject: Recipes that state Original Gravity - is that Pre Boil? Reply with quote


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I'm going to be brewing my first batch with my electric brewery this weekend. Brewing a Kolsch that has an original gravity specification of 1.041.

Now if I shoot for a Pre-boil gravity of 1.041 and I boil for 90 minutes - it seems that with almost a 3 gallon loss to evaporation - my post-boil gravity would be maybe about 1.046.

So for example - I am using Beersmith and I put the ingredients in with the given ratio until it tells me that I'll get my target of 1.041, which I assume is the estimated gravity out of the mash (pre-boil). Is that what I should be going for?
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Castermmt



Joined: 03 Jan 2011
Posts: 864
Location: Lowell, In

Drinking: Steelhead Porter, Alt-Toids, Hefty-Weizen, Terry's Kolsch, African Amber, Pumpkin Ale, Double Dog Ale

Working on: Janet's Brown Ale, Terry's Kolsch, Pilsner


PostLink    Posted: Fri Apr 04, 2014 12:45 am    Post subject: Reply with quote

Original Gravity is what you finish with after the boil and into the fermentor. The Original Gravity is the specific gravity measured before fermentation.

http://en.wikipedia.org/wiki/Gravity_%28alcoholic_beverage%29#Original_Gravity_.28OG.29.3B_Original_Extract_.28OE.29

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kal
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Joined: 12 Dec 2010
Posts: 10738
Location: Ottawa, Canada

Drinking: German Lager, Electric Creamsicle, London Pride, Kolsch, Belgian IPA, Red IPA, Russian Imperial Stout, Black Butte Porter

Working on: Weizen, Belgian Quad, Wit, English Pub Ale, Electric Creamsicle


PostLink    Posted: Fri Apr 04, 2014 4:09 am    Post subject: Reply with quote

Castermmt is correct. OG is the gravity you get going into the fermenters. Remember that if you're using a hydrometer, that it's only relative to whatever temp the hydrometer is calibrated to, otherwise you may need to adjust.

I know many people who use hydrometers and simply measure the gravity and completely ignore temp. That would be incorrect.

More info here: http://www.theelectricbrewery.com/parts-list-using?page=7

Kal

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TTodd



Joined: 11 May 2013
Posts: 21



PostLink    Posted: Fri Apr 04, 2014 7:56 pm    Post subject: Reply with quote

OK - so I'm assuming that all the brewing software like Beersmith and Brewer's Friend are showing Pre-Boil gravity ( I kinda tested this by changing the boil time and saw that the OG didn't change).

So if a recipe calls for a specific OG, let's say for example 1.050. When I enter the recipe into Beersmith - the "Estimated Original Gravity" that it is telling me is Pre-Boil, correct? Assuming so - then I would assume that I would need to shoot for a lower number to account for the increased gravity based on boil-off, is that correct?

Assuming the boil kettle volume of 14 gallons at 1.050. If I were to boil that for an hour or so to where the post-boil volume is 12 gallons, according to the Brewer's Friend "Dilution and Boil Off Gravity Calculator', my post-boil gravity would be 1.056. Now if I play around with the numbers if I wanted to get to a Post-Boil gravity of 1.050 (assuming 14 gallons preboil and 12 gallons postboil) I should be starting with a gravity of 1.043.

So my question is - when following recipes and trying to stick to the specified OG - should I be adjusting the grain bill in the brewing software to account for this boil-off gain in gravity?

(I hope all that makes sense)

Thanks in advance!
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kal
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Joined: 12 Dec 2010
Posts: 10738
Location: Ottawa, Canada

Drinking: German Lager, Electric Creamsicle, London Pride, Kolsch, Belgian IPA, Red IPA, Russian Imperial Stout, Black Butte Porter

Working on: Weizen, Belgian Quad, Wit, English Pub Ale, Electric Creamsicle


PostLink    Posted: Fri Apr 04, 2014 8:07 pm    Post subject: Reply with quote

TTodd wrote:
OK - so I'm assuming that all the brewing software like Beersmith and Brewer's Friend are showing Pre-Boil gravity ( I kinda tested this by changing the boil time and saw that the OG didn't change).

So if a recipe calls for a specific OG, let's say for example 1.050. When I enter the recipe into Beersmith - the "Estimated Original Gravity" that it is telling me is Pre-Boil, correct?

No. As mentioned above, OG is alway after the boil. What you get into the fermenter.

Don't know about other software, but Beer Tools Pro ONLY has post (after) boil gravity. I imagine most software would be the same as that's the only thing that makes sense since pre-boil gravity depends on how much you boil off, so it will vary from system to system as everyone has a different boil off rate.

Work your recipes to get to the OG gravity (post boil gravity) using whatever efficiency your setup gets. Then collect enough wort to fill the boil kettle to the pre-boil VOLUME, since you know how much you boil off. The first time you use your system you have to guess your boil off rate (and efficiency for that matter). Mine's 1.9 gal/hr based on 85% duty cycle on my boil PID, always ending up with 12 gallons post boil. That's probably a reasonable place to start. For efficiency I recommend that people start at around 85% for the first time if building the setup I document here. I hit 88% on my first brew and then it crept up slowly over the next few batches as I got better at using the system and started to pay attention to mash pH.

Quote:

So my question is - when following recipes and trying to stick to the specified OG - should I be adjusting the grain bill in the brewing software to account for this boil-off gain in gravity?

No.

Adjust the grain bill to account for your system efficiency to hit the desired OG (this is post boil gravity).
Then adjust the amount of wort you collect in the boil kettle based on your boil off rate to hit your final (post boil) amount that your recipe expects you to get (ex: 12 gallons @68F).

For more info, see my BREW DAY STEP BY STEP article. It walks you through a lot of this.

Kal

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