Help with inexplicably low original gravity

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I am looking for advice on an inexplicably low original gravity. My pre-boil gravity was correct. My boil off rate was correct. So how can my OG be so far off? I've attached my recipe created in Beersmith. Here's the details...

I have tried brewing a Bell's Two Hearted Ale clone twice; just one month between brew days. This is an all grain recipe mashed at 150F for 1-hour. Followed by a 10-minute "mash out" at 170F. Both times, I have had a successful mash (confirmed with iodine test), and hit my pre-boil gravity figure. Per Beersmith, my preboil gravity should be 1.054; mine measured 1.055 with a standard hydrometer after cooling the beer to 68F.

Here's where things get a little murky. I overshot my pre-boil volume a little bit. Beersmith called for 3.83 gallons. My measured pre-boil gravity was actually 3.96. So I had about 20oz more wort than expected, which I attribute to less grain absorption.

I then proceeded to my 75 minute boil. After 75 minutes, my post-boil volume (before chilling) was 3.30 gallons, instead of Beersmith's expected 3.21 gallons. (I started the boil with more volume, so this doesn't surprise me.) My boil off was measured at 0.65 gallons, just slightly more than Beersmith's expected boil off of 0.63 gallons. I use a 120v electric brewing system, so boil off is expected to be ~0.50 gallons per hour.

After the boil, I collected another hydrometer sample. Once chilled to 68F, I measured my OG at 1.060. Beersmith's expected OG is 1.067. This means my gravity only increased 5 points during the 75-minute boil. Beersmith expected a 12 point increase. I have experienced this low OG issue both times I have brewed this recipe. How much should I expect my gravity to increase if 0.65 gallons boils off?

I am starting to wonder if it's my recipe? Could it be the equipment profile in Beersmith account for such a difference? Or if there could be other factors impacting OG aside from per-boil gravity and boil off?

It's probably worth mentioning that I have been able to hit the numbers (pre-boil and post-boil gravity) calculated by Beersmith using other recipes on this same electric brewing setup (i.e., Anvil Foundry 6.5).

Final note - I know an OG of 1.060 is acceptable for an IPA. I was very pleased with how my first batch of this Two Hearted clone turned out. I just want to get to the bottom of why my OG is off target; it's frustrating!
 

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hotbeer

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My measured pre-boil gravity was actually 3.96.
You mean quantity? Certainly 3.96 is not your SG. You don't say if you added water to get to the 3.96 gallons after you measured the 1.055 SG post mash. Was that also post sparge?

Still, I would not be concerned about being 7 points off for one batch. If it was on every batch, then I'd know something more than random bad habits was up.


Brewersfriend has a dilution calculator you can play with the results of adding water and boiling off water.

I'm sure Beersmith must have something similar.
 
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PCABrewing

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I am looking for advice on an inexplicably low original gravity. My pre-boil gravity was correct. My boil off rate was correct. So how can my OG be so far off? I've attached my recipe created in Beersmith. Here's the details...

Once chilled to 68F, I measured my OG at 1.060. Beersmith's expected OG is 1.067.

Is your Hydrometer calibrated to 68 or 60? That will only result in ~.001 difference but good to know if you are measuring at the right temp.
 
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Evan Kingsbury
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You mean quantity? Certainly 3.96 is not your SG. You don't say if you added water to get to the 3.96 gallons after you measured the 1.055 SG post mash. Was that also post sparge?

Still, I would not be concerned about being 7 points off for one batch. If it was on every batch, then I'd know something more than random bad habits was up.


Brewersfriend has a dilution calculator you can play with the results of adding water and boiling off water.

I'm sure Beersmith must have something similar.
Sorry- 3.96 was the measured pre-boil volume in gallons, after sparging.

Thanks for the link to the boil off / dilution calculator. That calculator confirms that given my pre-boil volume (3.96), pre-boil gravity (1.055) and post boil volume (3.30) - my OG should be higher than 1.060. It should be 1.066 which is in line with Beersmith's calc. of 1.067.

1645388335884.png
 

hotbeer

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Yeah, that's what I came up with. It seems you just must have mis-measured something. Either the volumes or some SG readings.

Do you have kids and maybe when you left to use the restroom they thought they'd help you out by adding some more water?

Or maybe your brewing friends that were there pulling a prank on you, knowing how meticulous you are about numbers.
 
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Evan Kingsbury
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Yeah, that's what I came up with. It seems you just must have mis-measured something. Either the volumes or some SG readings.

Do you have kids and maybe when you left to use the restroom they thought they'd help you out by adding some more water?

Or maybe your brewing friends that were there pulling a prank on you, knowing how meticulous you are about numbers.
Haha, I don't have any kids in the house. I have brewed this recipe twice now, just one month apart. I ran into a low OG both times. Expected OG is 1.067. My first batch measured 1.062. My second batch measured 1.060.
 

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Did you sparge, or do no-sparge? If sparging, you need to stir the sparged wort aggressively with the first runnings wort, or you can have stratification. With stratification you have different SGs in different regions in the BK, that are higher or lower than the average SG. Depending on which zone you pull your sample from, your SG can read either higher or lower than the correct (average) value.

Boiling insures good mixing of all the wort, so you don't get stratification after the boil. For this reason, the post-boil SG measurement is often more reliable than the pre-boil SG.

If one, or more, of your SG or volume measurements is in error, then you won't be able to reconcile your pre- and post-boil measurements.

Brew on :mug:
 
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Did you sparge, or do no-sparge? If sparging, you need to stir the sparged wort aggressively with the first runnings wort, or you can have stratification. With stratification you have different SGs in different regions in the BK, that are higher or lower than the average SG. Depending on which zone you pull your sample from, your SG can read either higher or lower than the correct (average) value.

Boiling insures good mixing of all the wort, so you don't get stratification after the boil. For this reason, the post-boil SG measurement is often more reliable than the pre-boil SG.

If one, or more, of your SG or volume measurements is in error, then you won't be able to reconcile your pre- and post-boil measurements.

Brew on :mug:
Thanks @doug293cz! I did sparge with 1.47 gallons of water. (Which is a considerable portion of my pre-boil volume.) And I did not stir my wort after the sparge before taking my hydrometer sample from the spigot at the bottom of the kettle.

I can definitely see how my sugars could have been more concentrated at the bottom of the kettle where the spigot is. Following this logic, my pre-boil gravity reading could have been overstated. Which could explain why my OG is lower than anticipated.

I'll definitely be stirring my wort before collecting a sample for pre-boil gravity readings in the future. Thanks again.
 
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yamhill

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As I'm working through your scenario, I'm seeing some of the same things that have stumped me in the limited time I've had my Anvil Foundry (though mine is 10.5). After my first batch I struggled with the numbers. I then spent some time exploring a bunch of details -- like the accuracy of the volume measurements. I clearly should have done this at the onset, but diving into my first batch was a great learning experience too. I also measured dimensions and calculated volumes inside and outside the malt pipe, and much more.

If I understand the shared measurements correctly, it looks like you're losing gravity potential between the start and end of boil. Pre-boil 55*3.96=217.8 is more than post-boil 60*3.3=198. So, you lost more than water -- possibly indicating a measurement mistake.

What is the temperature of your post-boil volume measurement? If post-boil is volume is measured after cooling, thermal expansion/contraction between the two volume measurements is worth considering.

How are you measuring the volumes, and have you checked/calibrated the method?

Are you measuring the gravity with the same hydrometer/refractometer? (My last batch told me that I needed to recalibrate my refractometer.)

Does kettle trub factor in? -- Are you measuring the post-boil volume in the kettle or in the fermenter?

I'm geeky, and I sit down with my numbers and a spreadsheet after my brewing sessions to try and reconcile things. Hopefully some-day I'll get all those considerations done in real-time and check/recheck measurements in a meaningful way.

Good luck
 
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As I'm working through your scenario, I'm seeing some of the same things that have stumped me in the limited time I've had my Anvil Foundry (though mine is 10.5). After my first batch I struggled with the numbers. I then spent some time exploring a bunch of details -- like the accuracy of the volume measurements. I clearly should have done this at the onset, but diving into my first batch was a great learning experience too. I also measured dimensions and calculated volumes inside and outside the malt pipe, and much more.

If I understand the shared measurements correctly, it looks like you're losing gravity potential between the start and end of boil. Pre-boil 55*3.96=217.8 is more than post-boil 60*3.3=198. So, you lost more than water -- possibly indicating a measurement mistake.

What is the temperature of your post-boil volume measurement? If post-boil is volume is measured after cooling, thermal expansion/contraction between the two volume measurements is worth considering.

How are you measuring the volumes, and have you checked/calibrated the method?

Are you measuring the gravity with the same hydrometer/refractometer? (My last batch told me that I needed to recalibrate my refractometer.)

Does kettle trub factor in? -- Are you measuring the post-boil volume in the kettle or in the fermenter?

I'm geeky, and I sit down with my numbers and a spreadsheet after my brewing sessions to try and reconcile things. Hopefully some-day I'll get all those considerations done in real-time and check/recheck measurements in a meaningful way.

Good luck

@yamhill - thank you for your thoughtful response! Here are the answer to your questions...

Typically, I measure my post-boil volume in the kettle at the end of the prescribed boil time. I do this to make sure I'm in the right neighborhood in terms of volume before I start chilling. I measure my volume using the pre-stamped markers within the kettle. I have verified this markers are (at least close to) accurate in the past.

So all that to say, the wort is hot and trub is still included in my post-boil volume measurement. I also estimate that wort chiller displays about .33 to .50 liters. So I try to account for that in my measurement.

After I chill my wort and transfer it off of the trub, I take another measurement for "batch size" into the fermenter. Unfortunately, I forgot to measure batch size for this particular brew.

Based on all of the feedback I've gotten here, I've resigned myself to the fact that I must have made an error somewhere in my measurements. I'll just try have to try again!
 

yamhill

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It sounds like you're covering all the issues that I raised.

Are you using the stock wort chiller or something else? (Thinking outIoud...) I see the stock chiller at 3/8" and 28' -- or a volume of 0.6 liters or less if partially submerged, so with the stock chiller, your range looks reasonable there too.

I'll keep thinking on it -- or "wordling" (preoccupied with trying to find the right answer or next wordle guess) as it's now known in my house.
 

DuncB

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I'm with @yamhill
The numbers you have measured might not be the real world numbers due to thermal expansion not sure if the recipe program is compensating for this. From memory about a 4% increase in volume between 20 celsius and boiling. So your measured preboil volume appears more than it really was and similar for post boil.
As @doug293cz stratification is also an issue during sampling cool and warm liquids don't mix that well and also concentrated and dilute samples are surprisingly reluctant to mix.
Like you though the excitement to get brewing often gets in the way of the detail. Then when you try and finish the jigsaw several pieces are missing and other pieces are from another jigsaw.
Take lots of measurements, twice for each and average them. Check the calibration of your brew vessel markings, a half inch parallax error or a measurement of a rolling liquid can make a volume difference along with the measured temperature.
I often resparge the grains after removal from the boiler and have a look at the volume and gravity of that liquid and it's surprising what you leave behind.

That said a finer crush, lower mash pH and a longer mash ( checking the temperature in the grain bed) might improve your mash efficiency, then work on sparge effectiveness etc.
OR just accept the difference and build a bit more grain into the recipe.
 

yamhill

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After reading @DuncB, I just went and measured the level on the base of my anvil, a small stand (inverted milk crate and plywood :) ) on my garage floor. It's off by 1/4 in 18 inches. So, -- note to self -- the orientation of the anvil needs to be the same for all the measurements and from brew session to brew session if comparing, or better yet -- adjusted to level.
 

DuncB

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In an ideal world I'd have a weighing scale below my system and would just work on weight. It's a bit like golf if you always hit it left aim right, trouble is I'm a bit army golf left, right, left left right!
I've seen some people using a stick with measurements on that they put on the top edge of the " boiler " , you can colour code the measurements when you calibrate it for cool volumes and hot volumes. I do like to give the grains a really good squeeze down before and after the sparge ( i use my plastic jug to squeeze it down as it's hot stuff).
 
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