The numbers don't add up again...WHY?!?

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klnosaj

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The past two beers I've made have had the same problem. My pre-boil gravity is spot on. My pre-boil water volume is spot on. My post-boil water volume is spot on. Yet my post-boil into-the-fermenter original gravity is low. Isn't that kind of impossible?

Here are the details today:

------------------estimated -------measured

pre-boil SG---------1.040------------1.040

pre-boil H2O vol----7.0 gal-----------7.0 gal

post boil SG--------1.049------------1.043

post-boil H2O vol---5.25 gal----------5.25 gal

all estimates provided by beersmith 2.0, all measurements cross checked between hydrometer and refractometer, post-boil SG taken form two independent samples.


What is going on? I'm going crazy over this!:mad:
 
It's the trub dude

I thought of that. So I measured it. It's 2.5 quarts, and that includes all the solid matter. That means my total post-boil volume was 5.875 gallons. What it should've been, according to the software, is 5.82 gals. That's within the margin of measurement error, right? That's about 6 oz of water and, as I said, it includes the entire volume of solid hop debris. I think it's something else.
 
volume differences based on different temperatures?

I think BeerSmith takes care of that. Good suggestion, though. I guess it HAS to be a measurement error but it seems unlikely that I'd make the exact same error measuring two or three different batches over the course of a month. Nothing in my equipment has changed. I feel like I'm banging my head against a wall here and Lord knows I've already been doing that enough lately. If I could figure out where or what the measurement error is I could correct it but I have no idea why I'm off.
 
klnosaj said:
I'm wondering this: does wort boil off at the same rate as water?

I would say it boils off faster. The more dissolved solids are in water, the lower the boiling point.
 
You're definitely adjusting your hydro readings (using beersmith's lovely temp adjustment tool) to account for temperature? Hydro readings should all be adjusted to something like 62f or something.
 
If your volume measurements and thermometer are accurate, your measured post-boil OG is, shall I say, unpossible. :p

No way you can boil off nearly 1.75 gallons and only rise 3 gravity points.
 
If your volume measurements and thermometer are accurate, your measured post-boil OG is, shall I say, unpossible. :p

No way you can boil off nearly 1.75 gallons and only rise 3 gravity points.

I should clarify. The volume into the fermenter is 5.25 gals. The total post-boil volume should be 5.82 gallons. I measured 5.88 gals.

How are you measuring Post-Boil Vol? The measurement on the side of all my Ale Pails/Buckets is way off.

I've calibrated my carboys and I used a 2 qt measuring cup to measure the trub.

How much extra water would have to be present to account for 6 gravity points if the target is 1.049 @ 5.82 gals and the actual is 1.043. How do I solve for x there?
 
I should clarify. The volume into the fermenter is 5.25 gals. The total post-boil volume should be 5.82 gallons. I measured 5.88 gals.

I've calibrated my carboys and I used a 2 qt measuring cup to measure the trub.

How much extra water would have to be present to account for 6 gravity points if the target is 1.049 @ 5.82 gals and the actual is 1.043. How do I solve for x there?

My math says that if your 7 gallons of 1.040 wort was boiled down to 5.88 gallons, it should be at ~1.048.

For it to be at ~1.043, I calculate that to be ~6.5 gallons, based off of your original 7g of 1.040 wort.

Your post-boil OG reading is not reading accurate, for whatever reason, in my opinion....


*Disclaimer* my math may be bad. :eek:
 
My math says that if your 7 gallons of 1.040 wort was boiled down to 5.88 gallons, it should be at ~1.048.

For it to be at ~1.043, I calculate that to be ~6.5 gallons, based off of your original 7g of 1.040 wort.

Your post-boil OG reading is not reading accurate, for whatever reason, in my opinion....


*Disclaimer* my math may be bad. :eek:

I don' think the 7 gals is boiled down to 5.88. I think it's boiled down to 6.12 and then shrinks to 5.88 as it cools. I think that's how BeerSmith calculates the numbers, anyway. Maybe that's the problem?
 
I don' think the 7 gals is boiled down to 5.88. I think it's boiled down to 6.12 and then shrinks to 5.88 as it cools. I think that's how BeerSmith calculates the numbers, anyway. Maybe that's the problem?

What you need to do (to double check beersmiths numbers) is this. Take a volume measurement, temperature reading, and gravity preboil and post boil. Plug your preboil volume measurement and temperature into a thermal expansion calculator Use the temp you measured as the initial temp and 59F (or whatever temp your hydrometer is calibrated at) for final temp. Take this volume and your temperature adjusted hydro reading and figure out how many points you have. For example, 6.8 gal @ 1.040 = 6.8 x 40 = 272 points. Lets say you want 5.25 gal @ 65F in the fermenter and you have 2.5 qts of trub. That's 5.875 gal post boil. Adjust your post boil volume to 59F = 5.867 gal. You should have an OG of 272/5.867 = 1.046 ish. If your measured gravity doesn't match up with this, then something else is wrong. Like maybe your hydro is out of whack or your volume measurements are off.
 
What you need to do (to double check beersmiths numbers) is this. Take a volume measurement, temperature reading, and gravity preboil and post boil. Plug your preboil volume measurement and temperature into a thermal expansion calculator Use the temp you measured as the initial temp and 59F (or whatever temp your hydrometer is calibrated at) for final temp. Take this volume and your temperature adjusted hydro reading and figure out how many points you have. For example, 6.8 gal @ 1.040 = 6.8 x 40 = 272 points. Lets say you want 5.25 gal @ 65F in the fermenter and you have 2.5 qts of trub. That's 5.875 gal post boil. Adjust your post boil volume to 59F = 5.867 gal. You should have an OG of 272/5.867 = 1.046 ish. If your measured gravity doesn't match up with this, then something else is wrong. Like maybe your hydro is out of whack or your volume measurements are off.

I wish that calculator came in an English version. What am I supposed to enter for β - volumetric expansion coefficient (1/oC, 1/oF) ?
 
I wish that calculator came in an English version. What am I supposed to enter for β - volumetric expansion coefficient (1/oC, 1/oF) ?

If you scroll down there is a calculator. Enter your volume and temps and click calculate. It has already provided the ceofficient for you.
 
If you scroll down there is a calculator. Enter your volume and temps and click calculate. It has already provided the ceofficient for you.

Thanks a lot for the help. BeerSmith volumes check out. According to my calculations given what I've learned in the past few minutes, my actual end of boil volume was 6.06 gals rather than 5.875. That's a pint and a half (23.68oz to be exact) and I guess I could account for that in measurement error. For instance, I didn't include the hydro sample I took and that's a half a cup right there. Clearly I have to learn to be far more precise. I thought I'd cured myself of sloppiness but apparently not. And at least I learned that my boil off rate isn't what I thought it was. That's super helpful and will make it infinitely easier for me to dial my system in.

Thanks to all for the help.
 
This should be the easiest calculation of all, shouldn't it? If pre-boil volume is 7.0 gals and pre-boil gravity 1.033 then post-boil volume of 6.0 gals assuming a boil-off of 1 gal HAS to be 1.0385, right? Since 33 gravity points in 7 gals = 231, the same points in 6 gallons = 38.5. So why does beersmith tell me that my post-boil gravity should be 1.041? (My equipment profile is correct.)
 
This should be the easiest calculation of all, shouldn't it? If pre-boil volume is 7.0 gals and pre-boil gravity 1.033 then post-boil volume of 6.0 gals assuming a boil-off of 1 gal HAS to be 1.0385, right? Since 33 gravity points in 7 gals = 231, the same points in 6 gallons = 38.5. So why does beersmith tell me that my post-boil gravity should be 1.041? (My equipment profile is correct.)

I don't know. Just running some rough numbers (accounting for probable temps) I got ~1.038 for your OG. Not sure why Beersmith puts you 3 points higher. This is why I like to use my own software via Excel. I know how the calculations are set up and can easily identify causes of discrepancies if they arise.
 
i'm reading this thread with great interest. I have a simiar but opposite problem. My OG is always higher than Beersmith says it should be. yet everything else has always lined up: preboil gravity, preboil volume and post boil volume (after trub loss). I have posted about it on the forum and have just got a 'your measurements are off response'.

I'm beginning to think that like OP I need to be more accurate in those measurements but there is also a lot of black box calculations going on in Beersmith that I need to figure out so I can adjust my inputs right in the software.

an interesting read and good points in here.
 
TacoGuthrie said:
i'm reading this thread with great interest. I have a simiar but opposite problem. My OG is always higher than Beersmith says it should be. yet everything else has always lined up: preboil gravity, preboil volume and post boil volume (after trub loss). I have posted about it on the forum and have just got a 'your measurements are off response'.

I'm beginning to think that like OP I need to be more accurate in those measurements but there is also a lot of black box calculations going on in Beersmith that I need to figure out so I can adjust my inputs right in the software.

an interesting read and good points in here.

I would just adjust your efficiency
 
i'm reading this thread with great interest. I have a simiar but opposite problem. My OG is always higher than Beersmith says it should be. yet everything else has always lined up: preboil gravity, preboil volume and post boil volume (after trub loss). I have posted about it on the forum and have just got a 'your measurements are off response'.

I'm beginning to think that like OP I need to be more accurate in those measurements but there is also a lot of black box calculations going on in Beersmith that I need to figure out so I can adjust my inputs right in the software.

an interesting read and good points in here.

I agree with bottlebomber. Have you adjusted your efficiency? I know that's not my problem (would that it were and the problem could be solved!) since my pre-boil gravity is correct. There's got to be something screwy with the beersmith water volume calculations as far as I can tell. I've also posted to that forum and am still awaiting a response. I'll definitely update here if I get any news.

Meanwhile...anybody else have any other ideas or experience with the same or similar problems? I wish I knew what I was missing:confused:.
 
Is it possible you're doubling counting losses somewhere trub, volume, etc.)?

aka, you're entering a corrected value and beersmith is also "correcting" it?
 
Is it possible you're doubling counting losses somewhere trub, volume, etc.)?

aka, you're entering a corrected value and beersmith is also "correcting" it?

I don't think so. And what's annoying is that the post-boil numbers add up. As I've admitted I can be sloppy with my volume measurements but there's something that just doesn't make sense to me in how beersmith is calculating the number. If I have x gravity points in y gallons of water than the points I have in y-boiloff is an easy thing to calculate. But beersmith is getting it wrong.

I'm wondering if it doesn't have something to do with temperature and expansion under temperature. I begin with 7 gallons of H2O at room temperature and use that for mashing and sparging. I then put 7 gallons of wort, now around 160F into the kettle and boil that for an hour until I have 6 gallons of ~212F. That shrinks and I toss the trub and I'm left with 5.25 gallons of room temperature wort. So is the software making assumptions about temperatures or something? I would LOVE it if someone could explain this to me.
 
I'm wondering if it doesn't have something to do with temperature and expansion under temperature.

Not sure about beersmith, but in beertools, pre boil volume is shown @ 212. If beerstools tells me I need 7.15 gal, I will collect 7 gal @ 140 since it will expand. Likewise, it shows post boil volume @ 68, so you need to correct for that too.

Another thing to check: do you recirculate through a CFC during the boil? I was pulling my hair out for a while until I realized that I had to add compensate for the wort in the CFC and tubes since it wasn't there when I take my pre-boil reading.
 
are you 100% sure your chiller isn't leaking water into the wort?

I had that happen once (and no, the beer was fine, damn good in fact)
 
This should be the easiest calculation of all, shouldn't it? If pre-boil volume is 7.0 gals and pre-boil gravity 1.033 then post-boil volume of 6.0 gals assuming a boil-off of 1 gal HAS to be 1.0385, right? Since 33 gravity points in 7 gals = 231, the same points in 6 gallons = 38.5. So why does beersmith tell me that my post-boil gravity should be 1.041? (My equipment profile is correct.)

You say "assuming a boil-off of 1 gal", but is that the actual number in the equipment profile you're using? What about settings for trub losses, etc?
 
Not sure about beersmith, but in beertools, pre boil volume is shown @ 212. If beerstools tells me I need 7.15 gal, I will collect 7 gal @ 140 since it will expand. Likewise, it shows post boil volume @ 68, so you need to correct for that too.
This is the tree I'm barking up right now. But it's weird to me that nobody else seems to have these same problems. I did a bunch of fake batches using made up profiles and I found the error to be a roughly inverse proportion to the size of the grain bill. 90% of what I make are between 1.040 and 1.045 and I'm looking at only a 90% accuracy from beersmith. If I were doing huge beers the software gets it closer to 97% right.

Another thing to check: do you recirculate through a CFC during the boil? I was pulling my hair out for a while until I realized that I had to add compensate for the wort in the CFC and tubes since it wasn't there when I take my pre-boil reading.
Good looking out. As it is, though, no CFC for me. Just an immersion chiller :(

are you 100% sure your chiller isn't leaking water into the wort?

I had that happen once (and no, the beer was fine, damn good in fact)

Sounds like it wouldn't be a lot of fun to experience but I'm glad it worked out for you! This is another excellent suggestion but alas, my chiller is ship shape and leak free.

You say "assuming a boil-off of 1 gal", but is that the actual number in the equipment profile you're using? What about settings for trub losses, etc?
My boil-off rate is actually a little less than a gallon but that doesn't have anything to do with my point in the post above. What I was saying was that if you have a known quantity of wort x, with a starting gravity of y, then figuring out the gravity after a boil-off of any known amount is easy. I used 1 gallon in my example for the sake of simplicty but one could use any volume as long as it's known and calculate what the gravity of the remaining wort would be. Indeed, this is what the software doesn't seem to be doing correctly even though it's a calculation that's easily done on the back of an envelope. Thus my :(
 
no CFC for me. Just an immersion chiller

Do you put the immersion chiller in the kettle during the boil (after the pre boil reading is taken) ? That could make your post boil volume reading look higher than it really is.

What I found in my problem was that since I wasn't accounting for my boil volumes correctly (but not adjusting for the cfc volume), I was in turn calculating my apparent evaporation rate incorrectly. When I put this into beertools, it calculated an incorrect SG, even though the pre-boil gravity was correct.
 
I agree with bottlebomber. Have you adjusted your efficiency? I know that's not my problem (would that it were and the problem could be solved!) since my pre-boil gravity is correct. There's got to be something screwy with the beersmith water volume calculations as far as I can tell. I've also posted to that forum and am still awaiting a response. I'll definitely update here if I get any news.

I'm still trying to wrap my head around the information in this thread. But I brewed yesterday and had the same result. Using your format from pg 1 klnosaj:

------------------estimated -------measured

pre-boil SG---------1.056------------1.055

pre-boil H2O vol----7.0 gal-----------7.0 gal

post boil SG--------1.067------------1.060

post-boil H2O vol---5.98 gal----------~5.85 gal

I don't think adjusting my efficiency is the answer because if I do it drops all my gravity readings and pre-boil is always within a point.

Perhaps I'm not measuring my post-boil volume correctly, or accurately enough? I'm a little less that 5.5 into the carboy. I took the 1/2 cup sample too.

What is the most accurate way to measure trub? Trub volume must be completely different depending on hop amounts and whole vs pellet.

Did you ever get a response from Beersmith forums?
 
Here is my equipment profile. Anyone see any red flags in there?

2vshyj4.jpg


I do really want to know how to properly measure trub loss though.
 
TacoGuthrie said:
Here is my equipment profile. Anyone see any red flags in there?

I do really want to know how to properly measure trub loss though.

Your trub loss will differ slightly but when you rack out of primary and into bottling bucket the difference between the two volumes is your loss
 
I thought that in the equipment profile the loss to trub/ chiller was the bottom of the brew kettle.

Where do i account for that .5 gallon in my equipment profile?

Maybe that is my issue.
 
I've become convinced that my problem is with shrinkage (high-five if your brain just flashed to that Seinfeld episode). My error comes down to having an extra quart of volume somewhere. That's not a lot at all but obviously is enough to throw off gravity numbers significantly when dealing with fairly low-gravity beers. I haven't discovered where that extra quart is coming from but I really hope I can.
 

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