Author Topic: Hitting pre-boil SG....missing OG  (Read 3794 times)


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Hitting pre-boil SG....missing OG
« on: January 31, 2009, 06:14:50 PM »
I just finished my 7th all-grain brew session.  Since I started crushing my own grains, my past 4 brews have hit 85% efficiency into the boiler consistently. I'm hitting my pre-boil volumes exactly as planned and my SG as calculated on BeerSmith has been within a point every time. I also have figured out on my earlier brews how much trub loss/boil-off I have and other small losses to be able to hit my volume into fermenter spot-on. The problem I have is that my OG has been 5-6 points low on these past 4 brews which have otherwise had much better efficiency into the boiler. I have all the numbers plugged in for losses and I hit my final volume each time. I just can't figure out why the gravity is off by so much. It's not a huge deal I guess as the beers are still fantastic but I'm baffled as to why this is happening. My initial thought is that I am not boiling off quite as much as I planned but that should leave me more volume into the fermenter which isn't happening.  I also check the gravity at 60 degrees.  Thanks for any help!!
« Last Edit: January 31, 2009, 08:44:25 PM by Flic »

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Re: Hitting pre-boil SG....missing OG
« Reply #1 on: January 31, 2009, 08:49:49 PM »
  I would recommend adjusting your brewhouse efficiency down a bit as this will likely take care of your problem.  You can hit all the targets and still come in low because the OG is based primarily on the grain bill and brewhouse efficiency.

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Re: Hitting pre-boil SG....missing OG
« Reply #2 on: February 01, 2009, 06:47:54 AM »
Thanks for the reply.  That is a good suggestion as I have been using 70% as my Brewhouse Efficiency but I my actual B.E. has been about 65% or so.  I will lower this on my next brew and we'll see what happens.  I'd rather plan low and end up higher!

Offline MaltLicker

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Re: Hitting pre-boil SG....missing OG
« Reply #3 on: February 02, 2009, 06:08:33 AM »
.....because the OG is based primarily on the grain bill and brewhouse efficiency.

It is possible the grain selections are off slightly, and with a larger batch this might have an impact.  For ex, if you have 12# of generic 2-row selected with a PPG of 36, and you're actually using a pale malt with PPG of 34 that might result in a few points difference.  The more grain, the bigger the factor.