OG problem...

[Troutman47]

Hi all,

I'm having a little problem with my OG and I'm not understanding why!

I'm hitting my pre boil gravity spot on but when I take a reading after a 90 min boil I miss the OG by miles.

For example:- today's brew, an oatmeal stout, pre boil gravity 1.033, expected OG 1.043, actual OG 1.034
Last w/e an IPA, pre boil gravity 1.039, expected OG 1.049, actual OG 1.043.
My pre boil and post boiled wort quantities are as expected.
The pre boil reading is done in a trial jar and temp adjusted, the post boil in the FV at around 22˚C, but I've always done it this way.

The only thing thats changed is that now I'm using Crisp's MO and getting 90% mash efficiency I'm adjusting the recipe to suit, therefore using less grain but I'm hitting my pre boil gravity so I can't see it's anything to do with that!

Anyone have any thought on this please?

Cheers

[seymour]

Very interesting.

Maybe I misunderstand your question, but it seems quite a leap to expect a 1033 gravity to increase all the way to 1043 simply due to evaporation. Or from 1039 all the way up to 1049, right? I think you'd have to have a crazy hot rolling boil for a long time to reduce your volume by that much. If you have a typical boil strength and duration, the actual increase you're getting sounds reasonable to me. I could be wrong.

Did you use to use a hotter burner or a longer boil perhaps? Did you change from a shorter and wider boil kettle (with lots of surface area to encourage evaporation) to a taller and narrower one (which doesn't release as much to the atmosphere)? Has your quantity of hops change at all (which absorb liquid)?

[orlando]

What software, if any, are you using?

[Troutman47]

Hi Guys, I'm using the same equipment as always, nothing's changed.

Here's the results from a previous Jail ale ;-

Target Pre-Boil Gravity: 1.037 SG Actual Pre-Boil Gravity: 1.040 SG
Target OG: 1.048 SG Actual OG: 1.050 SG
Target FG: 1.012 SG Actual FG: 1.012 SG
Target Apparent Attenuation:: 74.9 % Actual Apparent Attenuation: 75.7 %
Target ABV: 4.8 % Actual ABV: 5.1 %
Target ABW: 3.7 % Actual ABW: 4.0 %
Target IBU (using Tinseth): 31.7 IBU Actual IBU: 30.8 IBU
Target Color (using Morey): 18.6 EBC Actual Color: 18.6 EBC
Target Mash Efficiency: 90.0 % Actual Mash Efficiency: 97.4 %
Target Fermentation Temp: 18 degC Actual Fermentation Temp: 19 degC

So you can see 10 degrees between pre boil and OG is not out the way.

The software I'm using is Beer Alchemy

Weird this one!

[seymour]

I believe you, that's just very surprising to me. Like I said, what you're getting now is more in line with my personal experience. It would seem what you were getting before was the anomoly.

A stupid question: how often do you add simple sugars to the boil kettle? Did you add sugar, invert syrup, glucose, etc, to your Jail Ale boil? Obviously, if your pre-boil OG measured only the grain sparge, and the post-boil OG measured the combination of sparge + sugar, that would explain a lot...

Question for the group: Is anyone else consistently getting a full 10 degree gravity increase from pre- to post-boil, without the addition of sugars?

[Troutman47]

No sugars added Seymour!

[JammyBStard]

Not sure it helps but 90/97% mash efficiency seems very high to me.

[Troutman47]

Just looking back at previous brews and they're all between 6-10 degrees higher than the pre boil gravity.

SinceI've been using Crisp's MO my efficiency has gone to 90%

[techtone]

Are you giving a good stir before taking the trial glass sample? Also what temperature are you taking the gravity, as I have found the temperature correction charts/calculators to be VERY inaccurate at higher temps.

[Cpt.Frederickson]

Are you giving a good stir before taking the trial glass sample?

+1. I've run off from the tap and syphoned from the top of the kettle and got two different readings post boil. Stir, and sample from the top of the brew I would say.

[Troutman47]

Hi Techtone,
What I do is run off the mash and top up into the boiler and get that set up while the batch sparge is going on.
Then I run off the sparge into the FV i'm going to use, once that's finished I pour it into the boiler so it should have a good mix when the two are added together.
I draw off a little and let it cool a bit, on yesterdays brew the reading was taken at 55˚C and read 1.020, corrected came out at 1.033.

The OG reading is after I have dropped it into the FV from a hight to aerate, I clear the froth and put the hydro in, yesterday the wort temp was 22˚C and read 1.034!

I think this has only started happening since I began adjusting the grain bill to suit the higher mash efficiency.

Cheers