Adding DME not in the recipe late in the game -- how do I estimate OG

edgarmsmith

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I got overly ambitious and tried to BIAB a 5.5 gallon Wee Heavy in a 10 gallon pot. I created the recipe, and ended up with an outrageous 17.75 lb grain bill. I ended up sparging and getting to my boil volume, but (as you probably imagine) I undershot my pre-boil gravity by a little bit -- about 7 points. I wanted this one strong, as I'm putting it away for awhile, so I decided to add some DME I had on hand for starters just to raise the OG a little. It dawned on me that I had no idea how to calculate the amount of DME to add. So......I dumped in the entire pound. Recipe called for 1.084, and I ended up at 1.097. Fermentation has stopped at 1.033, when the recipe called for 1.022. I don't mind that at all, as I like a viscous wee heavy.

If I try that in the future, what is a good calculation for the amount of DME to add? Is there a function in Brewer's Friend that will help? I looked, but I missed it.

Thanks in advance!
 
It would be a fixed number, I believe. 1 lb of DME adds 46 points per gallon, pre fermentation. It's a linear relationship to your actual volume. Add 1 lb to 5 gallons, and it's a 9 point (or so) raise to OG.
 
the beer recipe calculator will tell you this just add it to the recipe as a late addition
 
Next time try this:
existing gravity minus target specific gravity equals specific gravity underage
SG overage times beginning boil volume equals Total points to be added
Total points to be added divided by PPG for DME equals Pounds of DME to be added

For example, assuming the existing and target boil volume is 8 gal and your SG is 40 but you want it to be 50:
50 - 40 = 10
10 X 8 = 80
80 / 42 = 2.4 pounds of DME should be added

Not to complicate things, but this doesn't take into account that the added DME will add volume to the water. By my calculations, 2.4 pounds would add the equivalent of about .4 gal., but this my hastily done and questionable calculation. In any event the above approach will get you close.

If your target SG is higher than your Existing SG, then you'll need add an appropriate amount of water to lower the SG to your target.
 

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