Author Topic: Beersmith off on OG calculation  (Read 3790 times)

Offline SleepySamSlim

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Beersmith off on OG calculation
« on: February 15, 2009, 07:01:35 PM »
Just curious -- I brewed a Porter clone today -- the recipe is directly out of the Dec/Jan Brew Your Own special edition -- 150 Classic Clone Recipes ---- Page 14 Black Butte Porter.

The BYO recipe indicates a OG of 1.053 -- that is what I measured. BeerSmith predicted 1.047.

I've attached the recipe file
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Worst old feelin' that I've ever had ...
-Robert Johnson

Offline BeerSmith

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Re: Beersmith off on OG calculation
« Reply #1 on: February 15, 2009, 08:07:16 PM »
Hi,
  I don't know how BYO predicted the OG, but its pretty easy to verify this calculation by hand, and it does come out to 1.047.  You can refer to Daniels Designing Great Beers or any number of other books to get this.

  For the two big extracts, take the potential of each extract (1.044 for example), subtract one and multiply by 1000 which gives you the fractional points (1.044 => 44 points) contributed by that addition.  Multiply by the number of pounds of extract (44 points * 2.5lbs for example) to get 110 points for the first addition, 118.8 points for the second extract.  The steeped grains don't add much - only 6.5 points all together (steeping is generally < 10% efficient at contributing points).

  Add these together and you get 235.3 points contributed by the grains.  Now just divide by the number of gallons (5 gallons) and you come out with the number of points for the overall batch which is 47.0 points, or a OG of 1.047

  That's how we used to do it in the old days...so 1.047 is the correct OG estimate.

Cheers,
Brad
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Offline MaltLicker

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Re: Beersmith off on OG calculation
« Reply #2 on: February 16, 2009, 01:33:26 PM »
Right, and the two DME's I have loaded in my BSmith are 1.045 and 1.046 PPG.  For the math to match exactly, both the amounts used and every PPG of every grain used would have to match.  If the primary ingredients are off by much, it's enough to change the OG.  Four oz of some crystal, not so much. 

Offline SleepySamSlim

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Re: Beersmith off on OG calculation
« Reply #3 on: May 13, 2009, 11:37:55 PM »
While this question is a little old - I now have the answer. This recipe has .8lb of pale 2 row malt in the grains section and the "steeping" instructions are really more of a mini-mash process (now that I am familiar with that process). In fact I was astounded at how malty the mix was before I even added the LME.

So that is where the extra gravity came from - in fact when I switch the recipe type to partial mash the predicted OG is about right on.

Case closed -- and the porter came out pretty good as well.
Some people tell you the old walkin' blues ain't bad
Worst old feelin' that I've ever had ...
-Robert Johnson