Author Topic: Adding DME to correct Gravity  (Read 15565 times)

Offline max42

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Adding DME to correct Gravity
« on: July 08, 2011, 06:59:27 AM »
During my last brew session, I found my preboil gravity was 1.055 and the estimated preboil gravity supposed to be 1.062 (I collected the proper volume from the Mash and it was mashed at 153 for 60 minutes (standard IPA AG recipe kit).  I rapidly tried to determine if BeerSmith would help determine how much DME to add to get the gravity back on track and could not figure it out.  BTW I finished the boil without additions.  My OG ended up at 1.062 with an estimated OG of 1.077, again with the correct batch volume into the fermentor.  I'm not sure how I missed the efficiency this bad.  I batch sparge and always hit 70-75% OG efficiency.

While I can't determine what happened to make this drastic change in efficiency (used multiple thermometers, both a hydrometer and refractometer, all in agreement, had not changed the barley crusher gap  but have not rechecked it as yet) - what I'm really after is how BeerSmith can tell me how to adjust the gravity into the boil by adding DME.

Any help greatly appreciated, thanks!

Offline FUZZYV

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Re: Adding DME to correct Gravity
« Reply #1 on: July 08, 2011, 06:40:07 PM »
Let's assume your numbers are correct. You have 55 pts and want 62. You're short 7 pts / gal. I'll assume 7 gal pre-boil volume. You need to add 49 pts (7 pts X 7 gal) to get BG to target number for hop utilization. Typically DME runs 42 ppg so, 49/42=19 oz DME. YMMV

Offline MaltLicker

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Re: Adding DME to correct Gravity
« Reply #2 on: July 08, 2011, 07:14:21 PM »
I just threw one pound into an empty recipe and it yielded a OG estimate of 1.009, so nine points per pound for the default 44 ppg amber dry extract? 

Batch size assumption was five gallons, so math matches that of FUZZYV, just need to use batch size and not boil volume (1.044 / 5 = 1.009 per gallon.)  You're wanting to fix the final OG after the boil, so you use the batch size. 

When I've come up short, I have used two points per quarter pound with decent accuracy. 


Offline max42

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Re: Adding DME to correct Gravity
« Reply #3 on: July 08, 2011, 08:15:32 PM »
Thanks for both responses.  I now understand the math.  But it sounds like BeerSmith does not have a calculator, or a method within your recipe to help with this.

Offline FUZZYV

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Re: Adding DME to correct Gravity
« Reply #4 on: July 08, 2011, 08:37:39 PM »
Just a thought...If you are trying for a 77 pt brew, isn't your grain bill in the 16-17 lb range for a 75% MEE? (I'm assuming 7 gal boil to net 5 1/4 to primary) And then wouldn't you need some 9-9.5 gals of wort to extract the sugars at mash thickness = 1.1 qt/lb and sparge at a minimum of 1.1x1.5=1.65 qt/lb and assuming around 2 gal MLT losses? Aren't these high gravity brews problematic anyway?

Offline dharalson

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Re: Adding DME to correct Gravity
« Reply #5 on: August 04, 2011, 01:44:28 PM »
Fuzzy

I work my math based on the total points of sugar that I need post boil.
If I am after 5 gals into the bottles, I will what about 5.5 gals at the end of the boil.
If my target starting gravity is 1.050 then I need 5.5 gal x 50 pts per gal or a total of 275 pts.
Assuming a 75% efficency in the mash / sparge,  I need 275 / .75 =  367 pts in my grain bill.
That's 11 lbs of grain assuming 33 points per lb

Now if the preboil SG is below your estimate:
Again assume a starting gravity of 1.050 and 5.5 gals.
also assume an estimated preboil volume of 6.5 gal with an estimated preboil gravity of 1.042  (275 total points / 6.5 gal  =  42 ppg)
Now assume I measure a (temperature adjusted) preboil gravity of 1.038 in 6.7 gals
Actual total points is 38 x 6.7 = 255 pts;  I need (want) 275 so I am 275-255 = 20 pts short
Using DME at 42 points / lb you will need 20/42 lb or 7.6 oz of DME.

Easy!

David


Offline max42

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Re: Adding DME to correct Gravity
« Reply #6 on: August 05, 2011, 06:37:59 AM »
Thanks for the replies.  As a followup, I have a Droid and downloaded the Brewzor app, so while looking into it's capabilities I found that one of the calculators was a Gravity Correction.  I entered both the current and desired gravity along with the wort volume and it gave me 19.09 Oz of DME.  The good news is that this matches Fuzzyv's formula above.  My desire would be that BeerSmith have the same feature, that way I don't have to remember the formula and the points for DME, etc.  Maybe Brad can add such a calculator in a future upgrade.

 

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