Getting Some Puzzling Efficiency and OG Numbers

[Savage06]

I brewed a batch of beer this weekend and ended up having my OG be 1.080 which is 8 points below my target of 1.088. I'm usually at my gravity or a bit over typically however going through my checks and readings the numbers just aren't making any sense, or more likely I'm missing something.

I cold steeped my dark grains overnight added the strained liquid to the kettle and added the grains themselves to the tun at mash out so they were in there the entire vorlauf and sparge

Maris Otter Pale (UK) 7.0 lb 45 % Mash 38 3 °L
2-Row (US) 7.0 lb 45 % Mash 37 1 °L
Flaked Oats 1.5 lb 9 % Mash 33 2 °L

I mashed the 15.5 lbs of light grains above for 60mins as follows:

5.34 gal @ 167.6
keep at 155 for 60
add .62 gal at 212 for mash out (added dark grains as below)
Vorlauf until clear
Sparge with 3.23 gal (fly sparge keeping water 2in above bed until complete.

I took refractometer checks during the mash @30 - 16.4brix @60 - 20brix

The target gravity at 75% with the light grains is 1.078

Roasted Barley (US) 1.0 lb 5 % Mash 33 300 °L
Chocolate (US) 0.75 lb 4 % Mash 29 350 °L
Special B (BE) 0.5 lb 2 % Mash 34 115 °L

I cold steeped the dark grains overnight at a ratio of 2Qts-1lb I collected .75 gal of dark runoff and added right to the kettle.

My full runoff all said and done was 8 gallons and my refractometer checked in at 19 Brix.

I boiled for 90mins and ended up with 6.7gal a boiloff of 10.8% which is in my usual range.

My one mistake was not again using my refractometer for a post boil reading, I used my hydrometer after the wort was chilled and ended up with a reading of 1.080. Which just isn't possible given my earlier readings.

I calibrated my refractometer to distilled and it was perfectly at 0 brix.

I have never had any issues with my hydrometer either but I will doublecheck when I am home.

So anybody have any ideas what the hell is going on?

 

[chickypad]

Your preboil brix of 19 (1.079) at 8 gal must be incorrect. You had 17.75 lbs of grain including the dark grains. Even if you assume that whole grainbill has 36 ppg potential (some of those grains have less) that would be a max of 639 gravity pts at 100% efficiency. You supposedly got 1.079 on 8 gal or 632 gravity pts. Obviously you didn't get 99% efficiency. Maybe your wort wasn't well mixed. At 75% efficiency (including the dark grains) your preboil gravity at 8 gal should be in the neighborhood of 1.060 I think.

 

[Savage06]

Exactly, but can the stratification effect of the wort be that drastic? Shouldn't the heavier wort stratify on the bottom of the kettle? I just grabbed a sample from the top.

Your preboil brix of 19 (1.079) at 8 gal must be incorrect. You had 17.75 lbs of grain including the dark grains. Even if you assume that whole grainbill has 36 ppg potential (some of those grains have less) that would be a max of 639 gravity pts at 100% efficiency. You supposedly got 1.079 on 8 gal or 632 gravity pts. Obviously you didn't get 99% efficiency. Maybe your wort wasn't well mixed. At 75% efficiency (including the dark grains) your preboil gravity at 8 gal should be in the neighborhood of 1.060 I think.

 

[chickypad]

How do you collect the wort in the kettle - through a valve at the bottom or dumping it on top? I can't think of another explanation unless you read it wrong. How many homebrews in were you, sure it wasn't 16 brix?