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Specific Gravity Conundrum

nickofosho

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I just finished brewing an imperial milk stout this weekend and am getting some very perplexing gravity readings. The pre-boil/pot-mash gravity came in at 1.084 (which was pretty close to the BeerSmith estimate) and now the post-boil/OG gravity is 1.082! I had a 2gal boil off starting at 7.5 gal boiling down to 5.5 gal. I'm 99.9% sure I read the pre-boil gravity correctly and 100% sure I'm reading the post-boil/OG correctly.

The mash didn't go perfectly... Mashed in and temp started at 162? and took a bit of stirring to get it down to the desired 156?, which took about 20-30min. The mash was also pretty thick because I was maxing out my 10gal mash tun and had no room for rice hulls, so the runnings where super slow. I batch sparged.

Here is the recipe:

10 lbs Pale Malt (2 Row) UK
5 lbs Pale Malt, Maris Otter
3 lbs Caramel/Crystal Malt - 40L
3 lbs Oats, Flaked (1.0 SRM)
1.75 lbs Carafa Special II
1.5 lbs Barley, Flaked
12.0 oz Milk Sugar (Lactose)
0.75 oz Nugget [13.00 %] - Boil 60.0 min
1.00 oz Perle [9.30 %] - Boil 30.0 min
0.75 oz Nugget [13.00 %] - Boil 30.0 min
1.00 oz Goldings, East Kent [4.70 %] - Boil 15.0 min
2.0 pkg Irish Ale (Wyeast Labs #1084) [124.21 ml] (3L two step starter)

Any help/input is greatly appreciated.

Thanks!
 
Greetings Nick - Some questions:

1) What are you using to measure SG?
2) Are you doing a temperature correction on your sample?
3) Was the lactose in the batch with both pre-boil and post-boil measurements?
4) Have you experienced this issue with any other brew, or just this one?

It seems odd to only have dropped 2 points after a boil that evaporated 2 gallons.  Perhaps you can post your recipe so we can have a look.
 
1) hydrometer
2) yes
3) No lactose in the pre-boil, but beersmith calculates the change as minimal.
4) first time with this sort of issue...

Here is the recipe:

10 lbs  Pale Malt (2 Row) UK 
5 lbs  Pale Malt, Maris Otter
3 lbs  Caramel/Crystal Malt - 40L
3 lbs  Oats, Flaked (1.0 SRM) 
1.75 lbs Carafa Special II
1.5 lbs  Barley, Flaked
12.0 oz  Milk Sugar (Lactose)
0.75 oz  Nugget [13.00 %] - Boil 60.0 min
1.00 oz  Perle [9.30 %] - Boil 30.0 min
0.75 oz  Nugget [13.00 %] - Boil 30.0 min
1.00 oz  Goldings, East Kent [4.70 %] - Boil 15.0 min 
2.0 pkg  Irish Ale (Wyeast Labs #1084) [124.21 ml] (3L two step starter)
 
Greetings nick - I'm thinking you need to post the full BeerSmith recipe, not jut the ingredients. The ingredients don't really tell me much.  I'm more interested in seeing your profile(s) along with the readings you took in the process.

I just entered the ingredients list onto my BS Mobil using my equipment profile at 70% efficiency and I have a SG (post boil) of 1.117 which is light years away from the 1.082 you predicted.  Something isn't right.  Please post the full recipe file.

From the desktop, Select the recipe, right click, then select Export Selected.  Choose a location, save it and upload it to this thread.

Another thought: when was the last time you checked the accuracy of your hydrometer?  It's a long shot, but I would check it if for no other reason than to eliminate it from the equation.
 
Nick,
When I entered the ingredients into Beersmith it predicted a gravity of 1.121 for a 5.5 gallon batch. For a 7.5 gallon batch (your pre-boil volume) Beersmith predicts an SG of 1.089.

In my vast experience with mistakes (and I'm in the running for a World record), impossibilities like this are usually the result of more than one error.

Regrettably, although my experience in making mistakes is vast, my experience with correcting mistakes is half-vast. Good luck with chasing this one down!
 
Attached is the BeerSmith profile.

I'm starting to think what happened was that my first and second runnings didn't mix well in my my kettle, so when I took a sample from the kettle, which drains from the bottom, I only got wort from the first running. That means my efficiency was terrible, which is unusual, but at this point it seems to be the a reasonable explanation.
 

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  • Crema Imperial Stout.html
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Hi nick - I'm not going to be of any further assistance. The file you sent is not a BeerSmith file.  Also, it seems you're on to something with your inaccurate readings.

Good luck!
 
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