OG Way Off?

[Frozer860]

Brewed the recipe listed below. Brew day went great. Hit my temps and volumes, but I am thrown off by my gravity readings. I did just get a new refractometer and calibrated it with distilled water. See readings below.

Pre-boil volume: 8.9 Gal
Pre-boil Gravity: 1.048
Post boil Volume: 5.5 Gal (1.5 hour boil)
Post boil Gravity (OG): 1.054

I calculated 87% efficiency. So with that known and my final volume of 5.5 Gal I should have been at 1.078 OG. Any ideas how I got 1.054 on my refractometer? It has ATC and should have been cool enough while checking. I am currently at 1.007 after 7 days of fermantation. I just want to know what the ABV will be and what I did wrong.

Recipe Type:AG
Yeast:White Labs California ale
Mash at 154 for 60min. I had 70%eff
American Rahr (2 row) Pale: 11.50lbs
American Briess Crystal 20 1.00lbs
American Briess Light Munich 0.75lbs
American Briess Carapils 0.75lbs
American Briess Torrified Wheat 0.25lbs

Chinook (Pellet) 1oz 30min
Cascade (Pellet) 1.5oz 30min
Williamette (Pellet) 0.5oz 15min
Cascade (Pellet) 1.5oz 15min
Williamette (Pellet) 1oz 5min
Cascade (Pellet) 2oz Dry in secondary

 

[Qhrumphf]

You probably had inconsistent runnings for your preboil reading and your post boil reading was probably the accurate one.

Where did you get 87% from? From your preboil or from an assumption? 87% efficiency is very ambitious for most homebrewers (although perfectly doable). 70% is much more typical.

Also are you really boiling off 3.5 gals over 90 mins? That's an insane boiloff rate.

 

[day_trippr]

Hard to say what the ABV will be considering the huge discrepancy between expected OG and actual.
I plugged your numbers into BS3's Boil Off Tool and it agrees with your expectations - given those numbers.
If the pre-boil gravity was (way) off (low) then everything else would follow.
Otoh, if your post-boil refract check was bogus due to insufficient mixing who knows what's up?

If the refract post-boil reading was accurate, to get to 1.007 fg would require wlp001 to hit almost 87% apparent attenuation (~71% real) for an ABV of 6.2%.
That's a lot more likely than dropping from from 1.078 to 1.007. I don't think wlp001 could hit ~91% attenuation on its best day...

Cheers!
[corrected strain number]

 

[Frozer860]

Thanks for the replies. Efficiency is what beersmith calculated for me. Typically I am 75-80%. So I was also surprised with the high efficiency. The boil off is another wild variable. My bk doesn't have markings so I calculated the initial volume based on the depth and radius of it. But it definitely was very close to the top of my 10 gallon bk and 5.5 half went into the fermenter.

Another variable is the runnings you mentioned. I think i pulled a small sample from the bottom of the bk, it may have been before the mashtun was completely drained(though I don't remember for sure). I'm ok with the 6.2% . Maybe I should not be so inebriated during brew day and get better readings haha.

Any advice on when and how to get the most accurate refractometer readings? Just use a puppet?

 

[day_trippr]

Umm....a puppet?

I never drink during brewing. Bad juju. Weird **** happens...

Cheers!

 

[Frozer860]

Derr...pipette!

 

[day_trippr]

Ah - that makes more sense. Auto-correct victim, no doubt

I pull my OG reading from the fermentor just prior to pitching and oxygenating, and after giving the carboy a thorough rocking/swirling to homogenize what's in it. The pre-boil reading is taken at the conclusion of fly-sparging plus ~5 minutes of recirculating the boil kettle, again to thoroughly mix the volume...

Cheers!

 

[Qhrumphf]

Thanks for the replies. Efficiency is what beersmith calculated for me. Typically I am 75-80%. So I was also surprised with the high efficiency. The boil off is another wild variable. My bk doesn't have markings so I calculated the initial volume based on the depth and radius of it. But it definitely was very close to the top of my 10 gallon bk and 5.5 half went into the fermenter.

Another variable is the runnings you mentioned. I think i pulled a small sample from the bottom of the bk, it may have been before the mashtun was completely drained(though I don't remember for sure). I'm ok with the 6.2% . Maybe I should not be so inebriated during brew day and get better readings haha.

Any advice on when and how to get the most accurate refractometer readings? Just use a puppet?

It's all gravity readings preboil and how you sparge and lauter are part of it. It's like the extract top off problem. First and last runnings have wildly different gravities (unless you're brewing no-sparge in which case it should theoretically be pretty consistent throughout, and there's probably a more complicated issue going on) and if your preboil sample isn't a homogenous mix it's flagrantly unreliable.

I've had to do different things on different systems to get a homogenous reading. Some whirlpool during lauter and are pretty consistent on their own. Some I've just had to stir. One I had no option but to wait for it to boil a few mins and stir itself to get a reliable sample.

Just sampling from the bottom is an easy way to grab more first running than last, and lead to a falsely high reading. Which is what you saw.

 

[Frozer860]

It's all gravity readings preboil and how you sparge and later are part of it. It's like the extract top off problem. First and last runnings have wildly different gravities (unless you're brewing no-sparge in which case it should theoretically be pretty consistent throughout, and there's probably a more complicated issue going on) and if your preboil sample isn't a homogenous mix it's flagrantly unreliable.

I've had to do different things on different systems to get a homogenous reading. Some whirlpool during lauter and are pretty consistent on their own. Some I've just had to stir. One I had no option but to wait for it to boil a few mins and stir itself to get a reliable sample.

Just sampling from the bottom is an easy way to grab more first running than last, and lead to a falsely high reading. Which is what you saw.

This makes a lot of sense. I appreciate the advice!