Dialing-in Beersmith

Ok, so I've been brewing about 3 years now, and using Beersmith for about 2.5. As far as I can tell, I have all my numbers and settings punched in correctly. My problem is, I nearly always exceed the pre-boil gravity estimate, yet nearly always come up a bit shy on the post-boil reading. What would this imply? I always hit my water measurements/goals as well.

Well, if you mean when you test it prior to pitching, it could be something to do with sparging or not. I use the batch (dunk) sparge to get to boil volume. Just adding water would thin it down a bit, so I sparge.

Gravity readings mean nothing without a corresponding volume reading.

Here is what I do to configure BeerSmith to match my processes:

Measure your grains carefully. Know the weight you are mashing. [W(g)]
Measure the volume of water carefully as you measure it out for mashing. Measure it at room temperature. [V(in)]
Measure the total volume of wort collected preboil [V(pb)]
Measure gravity reading preboil [Sg(pb)]
Measure your gravity postboil [Sg(og)]
Measure the volume into the fermentor [V(f)]
Measure trub and wort left in kettle [V(t)]

You now need to correct the volumes for temperature. Your preboil volume should be at sparge or mash temperature and needs to be corrected to room temperature. Expansion is usually around 2.5% at 160F, so the corrected volume would be V(pb)/1.025 = V(pbc)

Take the gravity readings as close to the calibration temperature of your hydrometer as possible.

Your volume into the fermentor and the trub should be taken at yeast pitching temperature.

Calculations:

Your water loss to the grain is: [V(in) - V(pbc)]/W(g)

Your rate of water loss to boil is: [V(pbc) - V(f) - V(t)]/[time of boil]

There is a way to check your measurements by tracking gravity points.

Gravity points preboil: Gp(pb) = [Sg(pb)-1]*1000*V(pbc)
Gravity points postboil: Gp(ab) = [Sg(og)-1]*1000*[V(f) + V[t]]

Your gravity points pre-boil should be very close to the gravity points post-boil. If not, you have a measurement error somewhere in your system. My difference is usually less than 2% difference, which matches the accuracy of my measurements.

You can take the water absorption rate by the grain and the boil off rate and enter these into BeerSmith to help the program to be more predictive of your process. It usually takes around 2 to 4 brews to get the software dialed in for repeatable results.

I track all brews this way which helps to determine if I have changed something in my process and to account for seasonal changes.

Thanks for the response, but that really doesn't help. As I said in my original post, I always hit my water measurements (meaning, the numbers that I have manually put into beersmith - my equipment profile), and I do take all of those measurements - if I didn't, how would I know what to enter into beersmith in the first place?

Staylow said:

Ok, so I've been brewing about 3 years now, and using Beersmith for about 2.5. As far as I can tell, I have all my numbers and settings punched in correctly. My problem is, I nearly always exceed the pre-boil gravity estimate, yet nearly always come up a bit shy on the post-boil reading. What would this imply? I always hit my water measurements/goals as well.

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This equates to having a boil-off less than you have told beersmith

ie: Your true boil off is smaller than your telling the software. If your volumes are correct going into the fermentor this can still occur if you are losing volumes elsewhere.

Kettle trub
Kettle dead space
Hops absorption
Plate chiller/hoses dead space
Spillages
Gravity samples

These are all additional causes of lost volume, some large, some very small. All can contribute to overestimating your boil-off reading.

The other likely cause is inaccurate readings of pre-boil volume and pre-boil gravity.

Make sure you are measuring gravity at the correct calibration temperature and factoring in the correct shrinkage of 4% in the post-boil volume calculations (4% is set as default for post boil which is good, but 2.5% is a more useful value for calculating true mash efficiency based on preboil volumes and temperatures).

Make sure you measure kettle dead-space, hop absorption and kettle trub to come up with a fixed value of trub loss and kettle dead space in beer smith. This can remain unchanged from batch to batch assuming the hop bills do not change enormously.

In short, there are quite a few possible solutions.

Post a screenshot of your equipment profile. It may highlight some causes. It takes a bit of detective work sometimes to nail down these data errors. once you get it right Beersmith is amazingly accurate.

Staylow said:

Thanks for the response, but that really doesn't help. As I said in my original post, I always hit my water measurements (meaning, the numbers that I have manually put into beersmith - my equipment profile), and I do take all of those measurements - if I didn't, how would I know what to enter into beersmith in the first place?

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Lots of people take the measurements, but fail to do the calculations and update the calculated figures back into BeerSmith. BeerSmith does not take the actual results and use them. It just acts as a record of what actually happened.

In any rate, if you check your gravity points balance and it works out to be roughly equal pre-boil to post-boil, then the issue is with your boil off rate or extraneous losses as Gavin suggested.

I wonder if anyone really dials things in so well that you hit both numbers every time. Mine vary a point or two on either reading. Sometimes preboil is high and sometimes low, then OG could be high or low. There doesn't seem to be any relation It can be high and high, low and low, high and low or low and high.

The numbers are close enough that I don't feel any need for more adjustments to Beersmith. The beer has been great. My last comment was on a wheat beer with orange peel and coriander. My friend said it was better than Blue Moon.

kh54s10 said:

I wonder if anyone really dials things in so well that you hit both numbers every time. Mine vary a point or two on either reading. Sometimes preboil is high and sometimes low, then OG could be high or low. There doesn't seem to be any relation It can be high and high, low and low, high and low or low and high.

The numbers are close enough that I don't feel any need for more adjustments to Beersmith. The beer has been great. My last comment was on a wheat beer with orange peel and coriander. My friend said it was better than Blue Moon.

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Pretty much where I am now. I just about always hit my volumes, at least within my ability to measure accurately. As with you, if I am a point off in either direction, I'm good.

It really boils down (pun not intended) to being repeatable in your process. Having the software fairly accurately predict my outcome has helped with the repeatability and being diligent in calculating and keeping my process tuned as I had described above has been instrumental in being repeatable.

I've noticed a significant swing in boil off winter vs. summer that, of course, doesn't match Beer smith's calculations. I'm looking at making a winter and summer equipment profile. Anybody tried that?

daveMN said:

I've noticed a significant swing in boil off winter vs. summer that, of course, doesn't match Beer smith's calculations. I'm looking at making a winter and summer equipment profile. Anybody tried that?

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what I was thinking. Also, I've seen threads about adjustments seasonally with dry environments, like the US Southwest.

daveMN said:

I've noticed a significant swing in boil off winter vs. summer that, of course, doesn't match Beer smith's calculations. I'm looking at making a winter and summer equipment profile. Anybody tried that?

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I have not tried this, though it makes sense.

I brew 20 liter batches outside during the late fall and 10 liter batches inside on the stove during the winter and early spring. I know there is a difference due to the BTU output of the gas stove versus the propane burner outside, so they have different profiles which may cover up some of the seasonal variation.

daveMN said:

I've noticed a significant swing in boil off winter vs. summer that, of course, doesn't match Beer smith's calculations. I'm looking at making a winter and summer equipment profile. Anybody tried that?

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Yes. Rises in humidity can reduce boiloff. But it has to be pretty big, typically people in dryer climates don't notice a swing in boiloff.

I'm in Minnesota. The indoor RH goes from about 30 in the winter to 60 in the summer. And that's with de- and humidification seasonally. I don't have a lot of data points but it looks like about a half gallon difference.

I had this exact same question since I also had an accurate PBG but relatively low OG the last two times I brewed. I'll take better notes this time and probably update my equipment profile in BS.

Thanks for asking.

Brewed last weekend and came up .5 gals short. Could've been a sparge problem instead of boil off loss though.

daveMN said:

Brewed last weekend and came up .5 gals short. Could've been a sparge problem instead of boil off loss though.

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You can figure it out by doing a sugar balance around the boil. The gravity points: [(hydrometer reading - 1) * 1000] times the pre-boil volume corrected to room temperature should be equal to the post boil gravity points [(hydrometer reading -1) * 1000] times the post boil volume (again corrected to room temperature.

If the readings are not within a couple % of each other, then the issue is with boil rate. If not, then you need to look at the accuracy of your readings OR with the amount of sparge water collected.

Oginme said:

You can figure it out by doing a sugar balance around the boil. The gravity points: [(hydrometer reading - 1) * 1000] times the pre-boil volume corrected to room temperature should be equal to the post boil gravity points [(hydrometer reading -1) * 1000] times the post boil volume (again corrected to room temperature.

If the readings are not within a couple % of each other, then the issue is with boil rate. If not, then you need to look at the accuracy of your readings OR with the amount of sparge water collected.

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Oginme- I did the calculations on my 4 AG batches last year and the results were eye opening.
Variations pre- vs. post-boil I could track back to differences in trub / kettle losses.
Pretty consistently I had close to 1.5 gal boiloff. I've been using 1 gal. Doesn't look seasonal so far.
The biggest thing, and I can't believe I didn't notice it, is that my pre-boil volumes were all over the place. Pre-boil gravity was inconsistent as well. Apparently I suck at sparging. Might try no-sparge next time to see if I can hit numbers that way. I missed all this just looking at a single batch at a time. And, I get to make more spreadsheets too, my other hobby.
Thanks for the help, guys. I would've been scratching my head on this for a while.

Oginme said:

You can figure it out by doing a sugar balance around the boil. The gravity points: [(hydrometer reading - 1) * 1000] times the pre-boil volume corrected to room temperature should be equal to the post boil gravity points [(hydrometer reading -1) * 1000] times the post boil volume (again corrected to room temperature.

If the readings are not within a couple % of each other, then the issue is with boil rate. If not, then you need to look at the accuracy of your readings OR with the amount of sparge water collected.

Click to expand...

Oginme- I did the calculations on my 4 AG batches last year and the results were eye opening.
Variations pre- vs. post-boil I could track back to differences in trub / kettle losses.
Pretty consistently I had close to 1.5 gal boiloff. I've been using 1 gal. Doesn't look seasonal so far.
The biggest thing, and I can't believe I didn't notice it, is that my pre-boil volumes were all over the place. Pre-boil gravity was inconsistent as well. Apparently I suck at sparging. Might try no-sparge next time to see if I can hit numbers that way. I missed all this just looking at a single batch at a time. And, I get to make more spreadsheets too, my other hobby.
Thanks for the help, guys. I would've been scratching my head on this for a while.