Hitting post boil og and boil off but missing FG? Weird situation.

[Colbizle]

This has been like the 3rd time this has happened recently and I don't understand how this is happening. Is it the cold a$$ weather?! I'm clearly missing something. I need a sanity check please!

For example, yesterday I brewed an IPA. (I use beersmith btw)

- Batch size is 5.5. I batch sparged and collected 7.50 gallons of wort.

- I got 80% efficiency. My target was 79%.

- My boil off is about 1.75-2 gallons (but the issue is it changes all the time. I live in MN and yesterday it was 1F outside with a "feels like" of -17F pretty windy).

- My pre-boil gravity was 1.050. In-line with beersmith calculations.

- Boil 60 minutes. A tiny bit off boil over during hot break but nothing major.

- End boil, wort chiller, I measure 5.15 gallons left, ok so I boiled a little more this time, it was cold out... take gravity reading. 1.060. My target is 1.067. I corrected with some DME and mumble on.

How is this possible? How can I boil off more than I want yet still under achieve my target OG? This hasn't been an issue before. Gravity points don't simply disappear! lol so frustrating.

 

[LLBeanJ]

How are you measuring your pre and post-boil volumes?

 

[Colbizle]

How are you measuring your pre and post-boil volumes?

Through beersmith which is based off my boil-off rate in my equipment profile.

 

[LLBeanJ]

No, I mean how do you know with certainty that you achieved your pre-boil and post boil volumes? Do you have a calibrated sight glass or markings on your kettle to ensure that you have accurate pre and post-boil volumes?

The sugar concentration in the wort is what it is. If you really had 7.5g pre-boil @ 1.050 and 5.5g post-boil, the resultant post-boil OG would have to be 1.068 (according to my math). However, if you believed it to be 7.5g and 5.5g, but was really something different, that would cause the expected post-boil gravity to be off.

 

[Colbizle]

No, I mean how do you know with certainty that you achieved your pre-boil and post boil volumes? Do you have a calibrated sight glass or markings on your kettle to ensure that you have accurate pre and post-boil volumes?

The sugar concentration in the wort is what it is. If you really had 7.5g pre-boil @ 1.050 and 5.5g post-boil, the resultant post-boil OG would have to be 1.068 (according to my math). However, if you believed it to be 7.5g and 5.5g, but was really something different, that would cause the expected post-boil gravity to be off.

Oh right. My spoon is marked off per gallon. It's the same spoon on the same kettle I've been using for 60+ all-grain batches.

 

[LLBeanJ]

Okay, so you're using a method that has proven to be correct in the past. Good.

Are you doing anything different to measure gravity? New hydrometer or refractometer? Correcting for temp? Can you think of anything in your wort collection, measurement, boil process that has recently changed?

Aside from that, I don't have much more to offer. You probably lost a little sugar in the boilover, but I agree with you that it likely wouldn't be enough to explain the discrepancy. Especially, if the previous batches that had the same problem didn't have any boilover issues.

 

[stratslinger]

My math definitely shows you should have been higher, if the volumes and gravities you list are accurate.

Preboil: you had 7.5 gallons @ 1.50, so 50*7.5=375 GU
Postboil: you had 5.15 gallons - the GU has to stay constant (sugars don't just disappear), so 5.15 * OG = 375, OG = 375/5.15, OG = 73, or should be 1.073.

So, you've already answered how you measured volume - how are you measuring gravity? Are you using a hydrometer or are you using a refractometer? In either case, is it calibrated, and are you making adjustments (if necessary) for temperature? Have you introduced some new tool in these last few brews (a new hyrdometer to replace a broken one? just get a refrac for Christmas?)?

Edit: Looks like LLBeanJ and I are thinking along similar lines!

 

[Colbizle]

Okay, so you're using a method that has proven to be correct in the past. Good.

Are you doing anything different to measure gravity? New hydrometer or refractometer? Correcting for temp? Can you think of anything in your wort collection, measurement, boil process that has recently changed?

Aside from that, I don't have much more to offer. You probably lost a little sugar in the boilover, but I agree with you that it likely wouldn't be enough to explain the discrepancy. Especially, if the previous batches that had the same problem didn't have any boilover issues.

LLBeanj thanks for help. I did get a new hydrometer, I bought the expensive lab grade one but I tested it along side the cheaper one and they both read the same with temp adjustments.

I also recently got a new false bottom, before I was using a threaded SS tube. Because of the new false bottom, I saw an increase of mash efficiency from 74% to 80% so I adjusted my equipment profile and beersmith recipe to that increase. Is it possible I didn't adjust my profiles properly? Here are some screen shots.

 

[Colbizle]

I noticed my total Eff and Est Mash Eff are the same. That doesn't appear to be right.

 

[LLBeanJ]

As far as I can tell, your profile settings look to be fine, At what point in the process did you pull the pre-boil gravity sample? Is there any chance that it was not mixed well and the sample was heavy on sugars? I usually pull mine as the boil is just coming up so that I know the entire volume is well-mixed between the first runnings and sparge.

 

[Colbizle]

As far as I can tell, your profile settings look to be fine, At what point in the process did you pull the pre-boil gravity sample? Is there any chance that it was not mixed well and the sample was heavy on sugars? I usually pull mine as the boil is just coming up so that I know the entire volume is well-mixed between the first runnings and sparge.

I check mine when everything is fully collected. I stir and scoop upwards to make sure all the sugars are well mixed in the wort. I take a reading then adjust for temp.

 

[LLBeanJ]

I check mine when everything is fully collected. I stir and scoop upwards to make sure all the sugars are well mixed in the wort. I take a reading then adjust for temp.

Makes sense. Just for grins, during your next brew session try pulling two pre-boil samples: one like you normally do it and another just as the boil starts and compare them. If I had to guess, I'd say it's possible that you pulled the heavier gravity wort up from the bottom for your reading, which skewed your sample. Not saying that's definitely what happened, but the possibility exists. Due to the convection of the boil and as long as you didn't add any top off water, the post-boil gravity should be accurate, which leaves the pre-boil gravity, which was mixed more or less manually, as the suspected culprit.

 

[Colbizle]

Makes sense. Just for grins, during your next brew session try pulling two pre-boil samples: one like you normally do it and another just as the boil starts and compare them. If I had to guess, I'd say it's possible that you pulled the heavier gravity wort up from the bottom for your reading, which skewed your sample. Not saying that's definitely what happened, but the possibility exists. Due to the convection of the boil and as long as you didn't add any top off water, the post-boil gravity should be accurate, which leaves the pre-boil gravity, which was mixed more or less manually, as the suspected culprit.

So are you saying maybe my efficiency is not as good as it say it is?

 

[stratslinger]

I noticed my total Eff and Est Mash Eff are the same. That doesn't appear to be right.

That's basically because you have 0 losses worked into your system there - if you started plugging in things like your Lauter Tun deadspace (if you just changed to a false bottom instead of a mesh tube, there's a very good chance this value has increased!), kettle losses due to trub, fermenter losses due to same, etc, then those two values would start to separate.

The weird thing I always dealt with was that I could never figure out then how to tweak Mast Eff in a recipe instead of Total Eff, so I just zeroed it all out and increased my batch sizes by a bit so I could manipulate total eff as if it were mash eff...

 

[LLBeanJ]

If my supposition above is correct and I have no idea whether it is, then yes, your efficiency would in fact be lower than expected.

Edit to add: Working backward from post-boil of 1.060 @ 5.15, your pre-boil should've been 1.041 @ 7.5g.

 

[LLBeanJ]

The weird thing I always dealt with was that I could never figure out then how to tweak Mast Eff in a recipe instead of Total Eff, so I just zeroed it all out and increased my batch sizes by a bit so I could manipulate total eff as if it were mash eff...

Pretty much the same here. I ignore mash efficiency and work only based on total efficiency. I set the actual inputs for pre/post gravities and volumes = to estimated. On brew day, I update them to reflect what I really achieved. This way, prior to brewing, actual = estimated and after brewing, actual = actual.

 

[Colbizle]

Interesting, I didn't know about the tun dead space. I'll go measure that once I get home and adjust my equipment profile accordingly. Thanks guys for the help!

 

[Colbizle]

FINALLY!! I figured out what was causing my issue of missing gravity points. Some searching on the beersmith forums gave me some insight but it all boiled down to (pun intended) my equipment profile and my brewhouse efficiency was off and my grainbill was too small for my mash efficiency. I was setting my brewhouse efficiency to my mash efficiency which was 80-83% and I was setting my loss to trub/chiller to 0 which made my mash efficiency to 80-83% so they were equal. According to beersmith your brewhouse efficiency is different than your mash efficiency as brewhouse takes into account losses during racking, fermentation, hops ect and thus requires you to up your grainbill to accommodate for these losses.

So I solved my problem by adjustwing my brewhouse efficiency to 73% and then I adjusted my "loss to trub/chiller" to .50. Which then moves my mash efficiency estimate to 83% which was my target.

I brewed today and hit all my numbers and my SG. WOO!