Pre Boil vs. OG - Home Brew Forums

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Old 10-15-2012, 02:06 AM   #1
May 2011
Oceanside, Ca
Posts: 396
Liked 15 Times on 13 Posts

Hey gang,

Is there a direct corelation between Pre boil gravity and OG? Meaning, a 1 hour boil in same equipment, similiar boil rate... will produce "x" increase in gravity?

I seem to float between .05 and .09 over the past 6 brews. Today seemed to be of the lowest and I am not sure why

Thanks in advance

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Old 10-15-2012, 02:12 AM   #2
Mar 2010
Cambridge, ON
Posts: 565
Liked 31 Times on 29 Posts

Usually, yes.

Atmospheric pressure, humidity, temperature, etc., all have a bearing on your boil off rate. As you brew more you'll figure out your average but there will be lows and highs. It's not fixed.

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Old 10-15-2012, 12:35 PM   #3
May 2012
Morgantown, Wv
Posts: 2,224
Liked 454 Times on 292 Posts

Yes but it's not linear in fact I think it's parabolic.

Gravity is the measure of the density of sugar in water so

A pre boil gravity of 1.040 is not going to increase as much over the same boil off rate as a 1.050 pre boil gravity.

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