Low OG, twice now

[rjstew]

So I brewed an all grain Imperial black IPA yesterday, the recipe is here: https://www.homebrewtalk.com/f12/stone-15th-anniversary-escondidian-imperial-black-ipa-clone-282914/

OG was supposed to be 1.101 but it turned out to be 1.075.

Strike water was 165 and I mashed at 151 or so but the temp varied depending on where I took it in my rectangular cooler. I stirred vigorously for at least 10 minutes but I couldn't get a consistent temp. One spot would be 159, another would be 140. (First of all, any idea why this was the case?) Total mash time was just over 60 minutes. I did the iodine test and conversion appeared complete. Eventually it evened out a bit around 151. I batch sparged twice at 15 minutes each. Sparge water was heated to 175. I used this calculator to determine all my mash/sparge variables http://www.brew365.com/mash_sparge_water_calculator.php. Total mash volume was 6.32 gallons, total sparge volume was 4.01 gallons. I ended up with about 8 gallons of wort, which was higher than what the calculator said but the exact amount the recipe said I should start my boil with.

I boiled for 90 minutes and when I was done I had about 6.5 gallons of wort, well over the 5.5 gallons that the recipe said I should end with.

This is the 2nd all grain I've done and this is now the 2nd time I've been 2 points below my target OG. I never had a problem hitting my OG with extract/partial mash brewing, obviously.

So my question is, was my OG low because I had an additional gallon of wort, thus diluting it? How did I end up with that extra gallon? Any other ideas why my OG is so low?

 

[Epimetheus]

Was the OG measured at 6.5 gallons? in that case, the OG if you boiled it down to 5.5 would be:

.075 * 6.5/5.5 = .089

and 89 is still well below 101.

 

[jmichaeldesign]

You're collecting too much wort. For high og recipes you may need to boil longer as it can be tough to sparge efficiently with high amounts of grain. For 5.5 gallons post boil you should be starting the boil with 6.5 to 7 gallons. You're efficiency doesn't seem to be the issue. You're just literally watering down the wort.

To collect 7 gallons of wort do the initial infusion with 3.5 gallons plus one pint per pound of grain.

Then sparge with 3.5 gallons.

As far as the temperature variance I'm guessing its the thermometer. I always fill the cooler with all the water then slowly pour in the grain while stirring. There will be some variation in the temp but not the 20 degree variance you measured.

I usually aim to hit my my temp a little high, then stir for a few minutes to drop a degree or two till I'm right on. If you need to cool it more, add ice, a little goes a long way and won't mess with the liquor volumes enough to really effect anything.

 

[rjstew]

Epimetheus, The OG was measured after the boil was complete and the wort was cooled. Not sure what you mean by ".075 * 6.5/5.5 = .089"

jmichaeldesign, I mashed with 6.32 gallons, sparged with 4.01 gallon. Those figures came straight from the brew 365 calculator. The recipe said it was a 90 minute boil, which is the time I boiled.

Should I have mashed/sparged with less water? If so, why is the calculator off? Your calculation says I should have mashed with 5.875 gallons, not the 6.32 from the calculator.

 

[rjstew]

Any other suggestions?

 

[MBTB]

Epimetheus is right. The equation he gave you means this; your O.G. of 1.075 times your post boil quantity of 6.5 gal. divided by the target post boil quantity of 5.5 gal. would have given you an O.G. of 1.089
I personally would have used twice the batch sparge water to get more sugar off the grain. Boil time is much longer but I consistantly get the O.G. I expect. Calculators are great tools, but sometimes you have to just use a "method" that works, especially on BIG beers. Better luck next time.

 

[MBTB]

I should add that I scale down BIG beers to 2 or 2.5 gallons because of limited mash tun and kettle volume.

 

[billl]

If you have more water with the same amount of sugar, then your OG will be lower. eg if you water a 5 gallon batch down to 10 gallon, you cut the gravity in half. Same thing for ending up at 6.5 gallons. The ratio is (expected)/(actual). Online calculators are great, but they are only a starting point. You'll need to take some notes to determine what your real world variables are. eg you boil off 1.5 gallons in 90 minutes on your setup.

Other than that, you are low because you aren't getting the same efficiency as your recipe is built on. Don't feel bad. If you read through the thread, it is full of people who tried this brew and came up way short on gravity. It is NOT EASY to hit your numbers with such a big brew. It has 19 lbs of grain with a sugar potential of about 684 points. A 1.101 beer has 556 points in 5.5 gallons. To get that, you would need to be at 81% brewhouse efficiency! That is pretty darn good for a homebrewer with an average beer and normal hops (they absorb wort). At 70% efficiency, you would get a 1.087 batch of 5.5 gallons or a 1.075 batch of 6.5 gallons.

So, you actually had a perfectly respectable brew day. 70% on a monster brew is solid for everyone and impressive for only your second brew. For future batches, just plug in 70% for your efficiency (maybe 75% for a smaller brew) and adjust the grains to get to your desired gravity.

 

[rjstew]

I appreciate the feedback Bill, your comments were extremely helpful.

I also now understand Epimetheus' post, which was helpful because even if I boiled down to 5.5 gallons after another hour, I still wouldn't have hit OG.

Definitely going to note all of this and use it for my next brew! Thanks everyone for your advice.

 

[TheHairyHop]

Do you tip your cooler when draining off the wort? My efficiency jumped about 9% when I started doing this. All the heavy, sugar rich wort sinks to the bottom and doesn't get drawn off if you don't tip.

Also, the temp difference might be because you had balls of dry grain

 

[hopcop]

When I first started all grain I had the same issues. My thermometer would read all over the place. I do what the previous posts suggested by pouring in my water first a few degrees higher, mix really well while pouring in my grain and mix until the desired temp is achieved. As for sparging amounts, I found that I get a boil off of 1.75 gallons per hour with my setup. I also know that with my grist ratio 1#/1.25qt, I will end up with 1gallon of first runnings after a 60min mash time. So I know at this point I need to have 7 gallons of total wort in my kettle after sparging. So I heat up 6 gallons of water to Sparge with and I always hit my OG (sometimes its better) and always hit my volume. I also adjust for the hop absorption depending on the amounts. I suggest taking really good notes and look for consistent patterns in your volumes and not rely on just calculators. It made my brews better and consistent. Remember each brew rig is different but the all calculators are the same.

Brew on!
Cheers

 

[rjstew]

Do you tip your cooler when draining off the wort? My efficiency jumped about 9% when I started doing this. All the heavy, sugar rich wort sinks to the bottom and doesn't get drawn off if you don't tip.

Also, the temp difference might be because you had balls of dry grain

I did tip my cooler and also rocked it back and forth to eek every bit of wort out.

I don't think I had balls of grain, I stirred for a good 10 minutes straight. Then let it sit for 10 minutes and then stirred again for 5 minutes. Then waited 15 and stirred again for 5 minutes. The temp was inconsistent for the entire hour. Really odd.

Lesson learned....I need to take notes and not rely on the calculators. I'm just so used to brewing being science (x+y=z) that I forgot to take into account my individual setup.

 

[peanasky]

It's still science, it's just that each equipment set-up is unique and the calculators we use don't/can't always account for that. Like others have said, more sparge water will give you a bit more sugar, but you'll have to boil longer.

Keep at it though!

 

[Friedclutch]

If you have not already, get a good mash paddle. My first AG batches were difficult using a long spoon to stir the mash. Fwiw... My first big beer came under target og and then came in high on fg!

 

[bottlebomber]

You got 60% efficiency, which while not great is pretty common efficiency for people who don't have a mill and are using HBS mills. The guy who made that recipe is getting over 80% efficiency, which is uncommonly high. I hate to nag, but as an all grain brewer you are going to constantly be having problems with efficiency until you get yourself a mill. Definitely put it on the list.

 

[olz431]

I actually made a stand for my tun that puts it on a 37* angle and have noticed an increase in efficiency, but I also changed to a batch sparge from fly sparge at the same time.