Confused trying to adjust pre-boil gravity

[guinsu]

I've had two AG batches come out with a low pre boil gravity so I have tried adjusting it with DME. Both times I didn't get what I expected and I am wondering if someone could point out where my math was wrong.

First I had an IPA with a PG of 1.044 in 6.8 gallons of water, expected was 1.052 in 6.25.

I used the equation on pg 37 of Designing Great Beers:
(52 *6.25 - 44* 6.8) / 45 = .56

So I added half a pound of DME but my original gravity was still low.


Today I did a wit: PG 1.038 6.25g expected: 1.045 6.25g
(45 * 6.25 - 38*6.25) / 45 = .97

So I add a pound of DME, I decide to check the preboil gravity this time and my preboil gravity was 1.059. Way higher than expected. I topped off a bit at the end to get my OG closer to what it should be.

I just remeasured my brew pot to make sure I was getting the volumes right and I was.

Does anyone else use this method from Ray Daniel's book? Can anyone see what I am doing wrong?

 

[BierMuncher]

I never worry about trying to dial in a pre-boil gravity. It is what it is.

I'd suggest you simply lower your expected efficiency by 5 points. This will insure you get a higher yield and you can always top off with water if you severely overshoot your OG.

It will take several batches for you to calibrate your system. In the meantime...be conservative on your anticipated efficiency.

 

[northernlad]

How low was the gravity of the IPA after adding the DME?
At your volumes, they were only .004 off before you added the extract.

 

[guinsu]

I didn't check the preboil gravity on the ipa after adding (silly me), I know I should have.

 

[northernlad]

I just realized you said final gravity.
To be on the same page...
PG= Projected Gravity (I call it first wort Gravity)
OG= Original Gravity (Into the Fermenter)
FG= Final Gravity (Post fermentation)

Your projected gravity was 52 @ 6.25gal
You got 44 @ 6.8gal
The difference in your PG was only .004 after you correct for volume differences. Adding .5lb DME should have more than taken care of your variance.
If you did not check this and only checked your FG then the difference you have in your FG is likely due to the attenuation of your yeast.

 

[guinsu]

Sorry, I mean to say preboil and original gravity, the beer is still fermenting.

 

[northernlad]

If my math is right (I don't have DGB in front of me) that .56lb DME should have added about .005 to your gravity putting it right where it should have been.
You could have just boiled down to 5.75 gal and left out the DME.

 

[Tonypr24]

is just me but I only check gravity after boil and chilled. Can the boil make the gravity go up? I dont use a bag for my hops and sometime when I take a sample for my gravity check i see alot of hop in the gravity scale, can this affect the gravity?