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Home Brew Forums > Home Brewing Beer > All Grain & Partial Mash Brewing > Why are my OG readings higher than calcs?
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Old 11-10-2012, 01:22 AM   #1
phxdiver
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Default Why are my OG readings higher than calcs?

Hi All,

Just brewed a 3 gallon batch of roggenbier yesterday and had a question on OG...It seems that I'm hitting a really high pre-boil efficiency as well as coming up with a higher than estimated OG (post boil) and am curious as to why...Below is my recipe...I'm using a brewmaster Ap for the iPhone for calculations...

3# 2 Row Pale Ale
2# Rye
1# Flaked Rye
1/2# rice hulls
.25oz Fuggles (4.2%AA) at 60, 45, 30, and 15 minutes
3t yeast nutrient @ 15m
1t irish moss @ 15m
Wyeast American Ale 1056

Process for this batch was as follows:

3gal water strike temp of 163...Measured temp of 150 in Igloo. Mashed 90 min. 2 gal sparge water at 170. Calc'd a mash tun loss of .25 gal and grain absorption of .75 gal. for total of 5 gal into mash and 4 gal for boil. Pulled exactly 4 galls, so that worked OK. Figured I'd lose about 0.6 gal during 60 minute boil and another .25 or so to trub when I rack for a total batch size of about 3 gallons, which is a perfect amount for me and gives me a reason for experimenting more often

My hydrometer reading for my pre-boil was 1.048 (at 60F exactly) versus calculated pre-boil of 1.040, backing into the efficiency, this means I pulled an 89% efficiency during mashing.

So, I adjusted the app's efficiency to 89% which showed my post-boil OG would be 1.054. My hydrometer reading of the post-boil (at 70F) was 1.061.

So I'm guessing my 90 min mash is probably helping out alot with my efficiency, along with a fairly fine grain crush (I use a Barley Crusher set at factory setting of .039) to get me an efficiency higher than the usual 75% standard.

Where I'm a little more confused is on the post-boil OG. Am I pulling in a higher OG reading due to a lower mash temp? I meant to hit a mash temp of 152, but my igloo was a bit cooler from being out in the garage. As I understand it, a lower mash temp will yield more fermentables and result in a thinner beer with more alcohol, so maybe this is the reason behind the higher OG, or am I missing something?

Thanks in advance for your inputs! Cheers!


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Old 11-10-2012, 01:47 AM   #2
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Are you sure your hydrometer is accurate?


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Old 11-10-2012, 01:55 AM   #3
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Are your volumes accurate?
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Old 11-10-2012, 04:44 PM   #4
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My hydrometer readings are usually within .001 or .002 of the calculated FG reading, so I'm thinking that isn't the issue and I did hit my volumes for both pre and post boil (4 gal and 3.6 gal)...Wondering if maybe the app assumes a different temperature during hydrometer readings??? Thanks.
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Old 11-10-2012, 05:09 PM   #5
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Your numbers are wrong. There is no way with the grain bill you posted you have 3 gal of 1.061 wort.
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Old 11-10-2012, 05:38 PM   #6
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Just because your hydro is close to your estimated numbers doesn't mean it's accurate. Test it in distilled water at 60 F and see what it says.
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Old 11-10-2012, 06:07 PM   #7
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Did you stir before taking the hydrometer sample?
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Old 11-10-2012, 06:41 PM   #8
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Quote:
Originally Posted by beerman0001 View Post
There is no way with the grain bill you posted you have 3 gal of 1.061 wort.
Why not? Putting the numbers in Beersmith if he really did hit 90% efficiency he would have that OG. I myself do think something is off, but just saying it's not impossible.


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Old 11-10-2012, 09:03 PM   #9
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I do not have beersmith plugged it in a tastybrew and could not hit that number. Set at 99% it says 1.056. LOL damn I missed the 1# flaked rye. so 89% is 1.061 duh


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Waiting on a tap. Maibock, Two Hearted, Pliny the elder, Chimay White, Roggenbrier, DFH60
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