Lower than expected O.G.

[Kbrann]

I had a question and I apologize if this has been answered elsewhere. Had trouble finding an answer and it seems like I don't get to many responses if I post a question on an old thread, so thought better to start a new one.

Just made a 10 gal. all grain IPA on Saturday and ended up with an O.G. of 1.060. We made the recipe on beersmith which gave an expected O.G. of 1.070. I cannot figure out what caused us to be so low. Our pre-boil gravity was higher than the expected so I don't think there was any issue with the crush, mash, or sparge. It seems like it just didn't go up enough during the boil.

We made this recipe once before, only making some slight tweaks this time around. Came out perfect the last time in terms of gravity. Unfortunately I did not have any D.M.E. around to raise it so I am going with it as is, but I am hoping to figure out the cause so it does not happen again.

The only cause I can come up with at this point is that right before we started brewing I noticed that beersmith had a boil off set for 0.5 gallons but our equipment boils off way more than that (about 2.75 gal, I know crazy).I adjusted this number prior to brewing which corrected my mash volumes, sparge volumes, etc. It did not, however, show the gravity being affected which I feel it should have since we wrote the recipe based on collecting 10.5 gal in kettle and then ended up collecting 13.25 gallons. Seems like a mistake on beersmith's part but I have never had any issues with this in the past.

 

[pricelessbrewing]

Either your volume was higher, or your efficiency was lower. Not enough information to determine which.

 

[helibrewer]

I had a question and I apologize if this has been answered elsewhere. Had trouble finding an answer and it seems like I don't get to many responses if I post a question on an old thread, so thought better to start a new one.

Just made a 10 gal. all grain IPA on Saturday and ended up with an O.G. of 1.060. We made the recipe on beersmith which gave an expected O.G. of 1.070. I cannot figure out what caused us to be so low. Our pre-boil gravity was higher than the expected so I don't think there was any issue with the crush, mash, or sparge. It seems like it just didn't go up enough during the boil.

We made this recipe once before, only making some slight tweaks this time around. Came out perfect the last time in terms of gravity. Unfortunately I did not have any D.M.E. around to raise it so I am going with it as is, but I am hoping to figure out the cause so it does not happen again.

The only cause I can come up with at this point is that right before we started brewing I noticed that beersmith had a boil off set for 0.5 gallons but our equipment boils off way more than that (about 2.75 gal, I know crazy).I adjusted this number prior to brewing which corrected my mash volumes, sparge volumes, etc. It did not, however, show the gravity being affected which I feel it should have since we wrote the recipe based on collecting 10.5 gal in kettle and then ended up collecting 13.25 gallons. Seems like a mistake on beersmith's part but I have never had any issues with this in the past.

The OG would not have changed in Beersmith after your adjustments....however the pre-boil gravity and pre-boil volume should have changed based on the adjustments.

You were over by 3 gallons, did you boil long enough to get your proper batch size? The extra 3 gallons pre-boil would certainly have lowered your pre-boil gravity to something below what Beersmith would have predicted.

 

[Kbrann]

The OG would not have changed in Beersmith after your adjustments....however the pre-boil gravity and pre-boil volume should have changed based on the adjustments.

You were over by 3 gallons, did you boil long enough to get your proper batch size? The extra 3 gallons pre-boil would certainly have lowered your pre-boil gravity to something below what Beersmith would have predicted.

We finished with 10 gal batch size as expected.

The expected pre boil gravity was 1.053. The actual was 1.057 which puts us at 77.3% mash effieciency. Recipe was based on 72% efficiency. Est. And actual preboil volume was 13.15 gal.

Into fermentor expected o.g. was 1.070, we hit 1.060

 

[pricelessbrewing]

Then you boiled off more, or left more trub/volume in the kettle than you input into the software

 

[Kbrann]

How did i boil off more when i started and ended with the correct volumes?

Also the end runnings gravity which i measured from the mash tun hose after i reached 13.15 gal in kettle was 1.045 so i definitely had enough sugars from the mash

 

[pricelessbrewing]

Sorry, I missed where you said you hit postboil volume.

In general:

If you preboil is higher than predicted, and your postboil is lower than predicted, then the only two possibilities are kettle losses (boil/trub/loss) are higher than expected, or one of your measurements are wrong. If you think your volumes are correct, then the most likely possibility is that the preboil mixture of first and second runnings was not evenly blended (happens often) and the sample you took was not representative of your preboil average wort gravity.

Sanity check:

13.15*57 = 749.55 total gravity points
10.00*60 = 600. So unless you left behind 2.5 gallons in the kettle as trub losses, you're missing some gravity points somewhere, which is indicative of an inaccurate measurement somewhere.

 

[doug293cz]

How did i boil off more when i started and ended with the correct volumes?

Also the end runnings gravity which i measured from the mash tun hose after i reached 13.15 gal in kettle was 1.045 so i definitely had enough sugars from the mash

An end of runnings gravity of 1.045 seams way too high, meaning you left too much sugar in the MLT. Usually for a fly sparge you should be under 1.020. Many brewers stop sparging and run-off if they get to 1.008 - 1.012, so end of runnings below 1.020 are common.

As Priceless said, your pre-boil SG measurement was probably distorted by taking a sample from a higher gravity region of an incompletely homogenized wort volume.

Brew on

 

[Kbrann]

I batch sparged not fly sparge, and realize 1.045 is high but does it matter since i had already collected 13 gallons from mash, or do u think it was a bad sparge so not as much sugar was rinsed out? This would definitely make sense if my preboil measurement was bad.

Thanks for the help, although now i have to figure out what caused us to leave so much sugar behind. I grind myself and have never had issues with the grind. We did have an issue with mash tun space because of the amount of grain in this recipe. When we were pouring the grain in we ended up having to drain 1 gallon out to avoid overflowing the mash tun, but after 15 minutes we were able to add the gallon back in once grain absorbed some water. Everything else seemed to go very smooth though.

 

[doug293cz]

I batch sparged not fly sparge, and realize 1.045 is high but does it matter since i had already collected 13 gallons from mash, or do u think it was a bad sparge so not as much sugar was rinsed out? This would definitely make sense if my preboil measurement was bad.

Thanks for the help, although now i have to figure out what caused us to leave so much sugar behind. I grind myself and have never had issues with the grind. We did have an issue with mash tun space because of the amount of grain in this recipe. When we were pouring the grain in we ended up having to drain 1 gallon out to avoid overflowing the mash tun, but after 15 minutes we were able to add the gallon back in once grain absorbed some water. Everything else seemed to go very smooth though.

From what you said in your posts, I inferred that you were fly sparging. Batch sparging makes things much easier to analyze. I did a simulation of your brew session based on your 13.15 gal pre-boil volume, 10.5 gal post boil volume, 72% assumed (mash) efficiency, and OG target of 1.070. I also assumed 0.12 gal/lb grain absorption and 0.125 undrainable volume for your MLT. Here is what I came up with:

• Post-boil volume: 10.5 gal
• Boil-off: 2.65 gal
• Pre-boil volume: 13.15 gal
• Grain weight: 28.8 lb
• Strike water volume: 10.16 gal
• Sparge water volume: 6.58 gal
• First runnings SG: 1.0775
• Sparge runnings SG: 1.0343 (vs. your 1.045)
• Pre-boil SG: 1.056
• Post-boil SG (OG): 1.070
• Mash efficiency: 72%
• Conversion efficiency: 89.4%
• Lauter efficiency: 80.6%

So, 1.045 for sparge runnings SG seems higher than it should be. Not sure how to explain that yet. If you supply your actual grain weight and volume measurements for some of what I assumed for the simulation, I might be able to shed some more light on what happened.

Brew on

 

[Kbrann]

Doug i gotta say you were pretty right on. I apreciate you helping out. At the end of the day im still confident the beer will be ok but when things dont work out as planned its good to know why. I attached some photos of my recipe and measurements on beersmith. Ignore ph because i didnt measure that and ignore anything after fermentation because its still in the primary.

 

[doug293cz]

I really would need to have strike volume and sparge water volume to do any more precise analysis. Didn't see those in what you posted. A screen shot of your equipment profile would also be helpful.

Brew on

 

[Kbrann]

I really would need to have strike volume and sparge water volume to do any more precise analysis. Didn't see those in what you posted. A screen shot of your equipment profile would also be helpful.

Brew on

Here ya go. Thanks for helping.