Calculated O.G. Much Higher Than Actual O.G.

Hey all,

I brewed my first all-grain batch recently and things actually went smoother than I was expecting. It is an American IPA and I used a total of 17 lbs of grain. I used a couple of brewing software products i.e. Brewology101.com to get an estimate of the expected O.G. before my brew day. For this particular brew, the estimated O.G. was suppose to be 1.094. I ended up with 1.072 which seems really low for 17 lbs of grain. I am wondering since this was my first go around with sparging, perhaps I didn't sparge properly. I used the batch method with 4.5 gallons at 170 degrees. I ended up with the 6.5 gallon pre-boil volume I was targeting, so the volume of water was not an issue. Maybe the temperature was too low? Should I have done more than one sparge?

Thanks for any tips!

The conversion happens during the mash. The sparge is at a higher mash just to rinse the grains.

The temperature of the mash could have been too high.

Remember MALT M=More A=Alcohol L=Lower T=Temperature

When you say OG, do you mean post or pre-boil?

What grains did you use?

I used 16 lbs of 2-row and 1 lb of Honey malt. I mashed at 150 and if anything it may have been slightly under 150, like 148. The O.G. was post boil. Is there a really clear documented batch sparging procedure out there on the Internet? I followed a YouTube video that in hind sight seemed lacking in detail.

Maybe the crush wasn't that good?

Also, using 70% and a theoretical average yield of 35 points per pound (assuming its not all 2 row) you end up with around 25 points per pound.
25 * 17 /5 = 85 not 1.094

If you ended up worth 72 instead of 85, thats around 60%.

When working with thicker mashes/more grain you can have lower efficiencies.
Might your mash thickness have been a little too high? Just enough to have lowered efficiency several points?

Your results are not really off that much.
Maybe stir more next time.

scruff311 said:

Hey all,

I brewed my first all-grain batch recently and things actually went smoother than I was expecting. It is an American IPA and I used a total of 17 lbs of grain. I used a couple of brewing software products i.e. Brewology101.com to get an estimate of the expected O.G. before my brew day. For this particular brew, the estimated O.G. was suppose to be 1.094. I ended up with 1.072 which seems really low for 17 lbs of grain. I am wondering since this was my first go around with sparging, perhaps I didn't sparge properly. I used the batch method with 4.5 gallons at 170 degrees. I ended up with the 6.5 gallon pre-boil volume I was targeting, so the volume of water was not an issue. Maybe the temperature was too low? Should I have done more than one sparge?

Thanks for any tips!

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+1 on the crush. I just adjusted my crush a little finer and got about a 6 % increase in efficiency. All other processes were kept the same. Once you dial that efficiency number in, the software will be much more accurate with its predictions.

60% really isn't that bad on a first try - especially with a higher gravity beer.

If you used 4.5 gallons of sparge and collected 6.5 total, that means you only had 2 gallons from the first runnings. For batch sparging, you want the 2 runnings to be about equal. You must have had a pretty thick mash with that much grain and that little strike water.

170 sounds a little low for the sparge water temp - what was it once you stirred it in?

My strike water volume was 4.25 gallons (using the 1 quart per pound rule) and unfortunately I didn't take a temp reading once I added the sparge water. When should I be stirring the mash? I guess I was afraid to lose heat and once the strike water was in, I gave it a quick stir and sealed the HLT up for an hour.

+1 on the crush, get a better crush and efficiency will improve.

You should stir about half way through the mash to mix things up IMO, work for me and you should also be stirring as you dough in to be sure you aren't getting doughballs. For sparging go to http://www.dennybrew.com Detailed instructions are there! Also make sure your sparge water is at least 170 to get a good rinse of those sugars

I 2nd checking the crush, and I find I get far better efficiency if I mash around 1.5 qts/lb of grain. I personally don't notice any higher efficiency stirring throughout the mash, but each system is different. I batch sparge with 180-190f water and stir like mad before collecting the 2nd runnings. Higher gravity beers can be hard to get decent efficiency

scruff311 said:

I used 16 lbs of 2-row and 1 lb of Honey malt. I mashed at 150 and if anything it may have been slightly under 150, like 148. The O.G. was post boil. Is there a really clear documented batch sparging procedure out there on the Internet? I followed a YouTube video that in hind sight seemed lacking in detail.

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Here is a good PDF from Bobby_M

ArcLight said:

Maybe the crush wasn't that good?

Also, using 70% and a theoretical average yield of 35 points per pound (assuming its not all 2 row) you end up with around 25 points per pound.
25 * 17 /5 = 85 not 1.094

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That's the same number I got

What was you're volume after the boil?
What was the gravity pre-boil?
How much strike water did you use?

You may want to increase your strike water to help with efficiency and it will give you more wort from the first runnings which will be a better wort.

Ideally you would want the strike volume and sparge volume the same but I would start with increasing your strike volume to get closer to 1.4-1.5qts/lb

once you get the wort in the kettle, take a gravity reading. Then you can calculate what volume you have to boil down to to get your target post boil gravity.

I usually try to get 7-7.5 gallons of wort in my kettle. Then when I transfer to the carboy, I can usually leave quite a bit in the bottom of the kettle to avoid tranfering the trub and still get the volume in the carboy I want.

If you sparged with 170 degree water, it was too low. This is prolly how I would have done it.

14lbs of grain shooting for 150 degree mash a preboil of 6.5 gallons and sparge at 175.

Strike 6.5 gallons at 162(I would prolly heat to around 166-167 and add to non-preheated mash tun, watch the drop and stir to cool til I get to 162). Then stir the ever living hell out of it. Take temp reading, wait ten min and take another reading. 60 to 75mins later Vourlauf and drain. Then add the 2 gallons of 210 ish degree water to reach a sparge mash temp of 170. Wait ten minutes then Vorlauf and drain.

Also as jetmac stated above I try to shoot for the same preboil volume of 7 to 7.5. After I whirlpool I loose a good bit to the cone from hotbreak.

"My strike water volume was 4.25 gallons (using the 1 quart per pound rule) and unfortunately I didn't take a temp reading once I added the sparge water."

It sounds like you are getting a little down on this brew, but honestly, you are pretty close. The reality is that there is absolutely no way on earth to know the particulars of your system without brewing on it a couple of times. You just found out a very valuable bit of data for your system that 1qt per LB only netted you 2 gallons of first running. You use that bit of data to improve the next brew. ie If you bump up the strike water to about 5.5 gallons, you should net out 3.25 gallons of wort on the first runnings or about 50%.

Add a bit more stirring , increase that sparge temp a bit and you will be well on your way towards dialing in your system. Congrats!

scruff311 said:

My strike water volume was 4.25 gallons (using the 1 quart per pound rule) and unfortunately I didn't take a temp reading once I added the sparge water. When should I be stirring the mash? I guess I was afraid to lose heat and once the strike water was in, I gave it a quick stir and sealed the HLT up for an hour.

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Yes you will lose heat. That is actually a technique to get a temp that is too high. Stir the heck out of it until it drops.

You don't need a temp reading of the mash when you start the sparge.

I typically heat my sparge to just under a boil, then I will store it in a 5 gallon cooler because I need the kettle to boil the wort. By the time I sparge, it drops to about 180F. If I remember correctly, anything over 168F is where you want to be. Remember, the sparge is just rinsing the grain, the conversion is(or should be) complete when you're done mashing.

I would imangine the grain absorbed about 1.5-2 gallons of water. IMHO you want the majority of the wort you are going to boil to be the first runnings. So if you want 7 gallons at the start of boil you need to get 4 gallons of first runnings in there. That would mean doughing in with probably 5.5 gallons of strike water. I'm not sure of the exact numbers, I'm not at home to run it through BeerSmith.

Thanks for all of your input. I've taken a lot of considerations and did some math of my own and came up with a couple of equations which should help me, much of which verified what some of you have already pointed out. I realized that if I am aiming for 50% first-runnings and 50% sparge, then the sparge should always be 1/2 of the desired pre-boil volume.

Sparge Volume = First-Runnings = (Pre-Boil Volume) / 2

Also, if we say the grains will absorb 1/8 gallons of water per pound, we have

Water Retention = 1/8 * Pounds of Grain

and

First Runnings = Strike Volume - Water Retention

if you combine these and solve for Strike Volume, for this specific brew (17 lbs of grain and 7 gallons of pre-boil) I get

Strike Volume = 5.63 gal
Sparge Volume = 3.5 gal

which works out to 1.32 qt per lb strike water. Yay .

scruff311 said:

Thanks for all of your input. I've taken a lot of considerations and did some math of my own and came up with a couple of equations which should help me, much of which verified what some of you have already pointed out. I realized that if I am aiming for 50% first-runnings and 50% sparge, then the sparge should always be 1/2 of the desired pre-boil volume.

Sparge Volume = First-Runnings = (Pre-Boil Volume) / 2

Also, if we say the grains will absorb 1/8 gallons of water per pound, we have

Water Retention = 1/8 * Pounds of Grain

and

First Runnings = Strike Volume - Water Retention

if you combine these and solve for Strike Volume, for this specific brew (17 lbs of grain and 7 gallons of pre-boil) I get

Strike Volume = 5.63 gal
Sparge Volume = 3.5 gal

which works out to 1.32 qt per lb strike water. Yay .

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Complicated but I like. You're on the right track