post boil gravity

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matc

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I'm having a hard time nailing my post boil gravity using beersmith. Do you guys have any idea ?

On my last few batches, the pre-boil gravity was always within 2 points of what beersmith predicted but for the post boil gravity, I often get 8 points lower than expected. I use an hydrometer that shows 1.0 in water so it can't be the problem.

I brew indoor with 2 elements that are always fully powered. My evaporation rate on beersmith seems ok with what I get and my volumes are spot on too. I'm lost...I start my 60 min boils as soon as I see big buggles breaking the foam on top.

Today's batch, an ipa, I nailed my pre-boil gravity and volume. After the 60 minutes boil, I was down to 16 L (beersmith said 17L) and my gravity was 1.058 instead of 1.068. I'm lost...I boiled 1 liter more than predicted but I'm still short of 10 points !!!


edit : If I boiled the wort for longer, my volumes would not match so I'm not sure how to fix this with beersmith
 
matc said:
I'm having a hard time nailing my post boil gravity using beersmith. Do you guys have any idea ?

On my last few batches, the pre-boil gravity was always within 2 points of what beersmith predicted but for the post boil gravity, I often get 8 points lower than expected. I use an hydrometer that shows 1.0 in water so it can't be the problem.

I brew indoor with 2 elements that are always fully powered. My evaporation rate on beersmith seems ok with what I get and my volumes are spot on too. I'm lost...I start my 60 min boils as soon as I see big buggles breaking the foam on top.

Today's batch, an ipa, I nailed my pre-boil gravity and volume. After the 60 minutes boil, I was down to 16 L (beersmith said 17L) and my gravity was 1.058 instead of 1.068. I'm lost...I boiled 1 liter more than predicted but I'm still short of 10 points !!!


edit : If I boiled the wort for longer, my volumes would not match so I'm not sure how to fix this with beersmith
Click to expand...

Adjust your target Pre boil volume. your obviously boiling off more than expected so just compensate up front. You may need to tweak some other parameters of your recipe but your Post boil gravity should be in line.

EDIT: I misread your post. That is odd. you boiled off more and still were short. Are you cooling your hydrometer samples?
 
yep I am cooling them...The only thing I can think about is that I made a mistake on my pre boil gravity but this is unlikely as I check 2-3 times to be sure
 
matc said:
I use an hydrometer that shows 1.0 in water so it can't be the problem.
Click to expand...

So your hydrometer is calibrated and you cool your samples. Scratch that.

matc said:
My evaporation rate on beersmith seems ok with what I get and my volumes are spot on too. I'm lost...I start my 60 min boils as soon as I see big buggles breaking the foam on top.
Click to expand...

What is your rate? Do you have the volumes (pre and post) from your last batch as reference? How long does it takes to get to your big bubbles?

matc said:
I nailed my pre-boil gravity.....After the 60 minutes boil, I was down to 16 L (beersmith said 17L) and my gravity was 1.058 instead of 1.068.
Click to expand...

What is your kettle size and geometry? Are you boiling off less than you think? What temperature do you cool your SG samples to?

Let's take a problem solving approach:

1.) Forget BeerSmith for a minute
2.) Pre-boil Gravity is what it is and you say your hitting yours. The only delta here would be you misreading your hydrometer. Taking your word as gospel here so that is out.
3.) Pre-boil volume is on point. Again, nothing to see here.
4.) You are boiling off more wort than predicted and missing OG. This is suspect. Again, the only red flag here at this point is either a mistake in reading the hydrometer or a mistake in measuring your volume Post-boil.
5.) If you are taking accurate readings with 60 deg. F wort and accurately measuring your volumes then you should be close OG wise.
 
(Pre-Boil_SG - 1) * Pre-Boil_Volume must = (Post-Boil_SG - 1) * Post-Boil_Volume

If it doesn't, then one or more of your volume or SG measurements is wrong, or you spilled a lot of wort. The amount of sugar in your BK is constant. Boiling does not evaporate any sugar. (SG - 1) * Volume is proportional to sugar weight, so if sugar weight is constant, then (SG - 1) * Volume also has to be constant.

What are your pre-boil SG, pre-boil volume, post-boil SG, and post boil volume? The last two have to both be measured before top off water, or both be measured after top off water. If one is before and one after, then you will get invalid results.

Brew on :mug:
 
doug293cz said:
(Pre-Boil_SG - 1) * Pre-Boil_Volume must = (Post-Boil_SG - 1) * Post-Boil_Volume

If it doesn't, then one or more of your volume or SG measurements is wrong, or you spilled a lot of wort. The amount of sugar in your BK is constant. Boiling does not evaporate any sugar. (SG - 1) * Volume is proportional to sugar weight, so if sugar weight is constant, then (SG - 1) * Volume also has to be constant.

What are your pre-boil SG, pre-boil volume, post-boil SG, and post boil volume? The last two have to both be measured before top off water, or both be measured after top off water. If one is before and one after, then you will get invalid results.

Brew on :mug:
Click to expand...

Buy this man a beer, he may have just cracked the case.
 
How are you measuring your volumes? Hopefully you've created your own calibrated method and are not going by the (very likely incorrect) markings on your kettle or fermenter?
 
pre boil sg was 1.051 (temp was 46 but I corrected it with a chart)
pre boil volume was 21 L, using my sight glass on my keggle. The sight glass was painfully calibrated using a water bucket and balance, 1 liter at a time.

Post boil volume was 16 L
post boil sg was 1.058.

I think I will begin by doing some tests on my keggle to make sure the sight glass is right.
 
doug293cz said:
(Pre-Boil_SG - 1) * Pre-Boil_Volume must = (Post-Boil_SG - 1) * Post-Boil_Volume

If it doesn't, then one or more of your volume or SG measurements is wrong, or you spilled a lot of wort. The amount of sugar in your BK is constant. Boiling does not evaporate any sugar. (SG - 1) * Volume is proportional to sugar weight, so if sugar weight is constant, then (SG - 1) * Volume also has to be constant.

What are your pre-boil SG, pre-boil volume, post-boil SG, and post boil volume? The last two have to both be measured before top off water, or both be measured after top off water. If one is before and one after, then you will get invalid results.

Brew on :mug:
Click to expand...

ok are my numbers right in your equation ?

(Pre-Boil_SG - 1) * Pre-Boil_Volume must = (Post-Boil_SG - 1) * Post-Boil_Volume

pre boil : (1.051-1) * 21 = 1.071
post boil : (1.058-1)*16 = 0.928

Obviously either my volumes or gravities are wrong ?
 
matc said:
ok are my numbers right in your equation ?

(Pre-Boil_SG - 1) * Pre-Boil_Volume must = (Post-Boil_SG - 1) * Post-Boil_Volume

pre boil :(1.051-1) * 21 = 1.071
post boil : (1.058-1)*16 = 0.928

Obviously either my volumes or gravities are wrong ?
Click to expand...

One or more has to be wrong (unless you spilled a lot of wort.)

Brew on :mug:
 
another question though....I ran the predicted beersmith numbers and came up with this..it seems impossible to get such a high OG with the pre boil gravity

predicted pre boil volume = 21 L,
predicted pre boil gravity = 1.052

(1.052-1)*21 = 1.092

predicted post boil volume = 17 L
predicted post boil gravity = 1.068

(1.068-1)*17 = 1.156

156-92 = 64 of difference. Maybe beersmith is totally wrong ???
 
It's either you sight glass is wrong or you hydrometer readings are wrong.

Was 1.051 your corrected SG?

I agree that it is a physical impossibility to boil off 1.25 gallons of wort and only get 7 gravity points. I'd be more inclined to say it's the sight glass.
 
matc said:
another question though....I ran the predicted beersmith numbers and came up with this..it seems impossible to get such a high OG with the pre boil gravity

predicted pre boil volume = 21 L,
predicted pre boil gravity = 1.052

(1.052-1)*21 = 1.092

predicted post boil volume = 17 L
predicted post boil gravity = 1.068

(1.068-1)*17 = 1.156

156-92 = 64 of difference. Maybe beersmith is totally wrong ???
Click to expand...

Your using liters. You need to use gallons with specific gravity.
 
matc said:
ok are my numbers right in your equation ?

(Pre-Boil_SG - 1) * Pre-Boil_Volume must = (Post-Boil_SG - 1) * Post-Boil_Volume

pre boil : (1.051-1) * 21 = 1.071
post boil : (1.058-1)*16 = 0.928

Obviously either my volumes or gravities are wrong ?
Click to expand...

It's:

(PBG*pre boil volume)/post boil volume = OG

(51*5.25)/4 = ~67 --> (67/1000)+1 = 1.067
 
matc said:
Maybe beersmith is totally wrong ???
Click to expand...

Unlikely. I bet both your sight glass and hydrometer are to cause for the discrepancy.

You say you measured your wort sample at 46°C (114°F) - that's way too hot! Yes, there are charts to adjust for temp differences between the sample and what the hydrometer was calibrated to, but they are only meant for relatively minor adjustments - up to say 20°F from calibration temp. That would mean you shouldn't be testing until the temp cools below ~80°-90°F (26°-32°C) minimum. Also, Beersmith has this tool built in ("Hydrometer Adjust").

Regarding the sight glass, I bet when you calibrated it you used room temp water? Hot wort will occupy a significantly larger volume than water at ambient temps. You can easily test this by adding a given amount of water (measured using the sight glass and at room temp), cover and heat it to near boiling. I bet the volume increases enough to throw off your readings.

I used my mash paddle to mark my volumes, and I have a different scale on 3 of the 4 sides. One scale for measuring room temp water (which will be heated for strike), one is calibrated for 165°F wort (for measuring lauter collection), and the last is calibrated to boiling volumes, for determining when I've hit my desired volume.
 
Derek1985 said:
It's either you sight glass is wrong or you hydrometer readings are wrong.

Was 1.051 your corrected SG?

I agree that it is a physical impossibility to boil off 1.25 gallons of wort and only get 7 gravity points. I'd be more inclined to say it's the sight glass.
Click to expand...

Are you sure the pre-boil wort is well mixed up and you are not measuring some early runnings that are higher SG, as opposed to the average value for entire wort.

In other words, is your wort homogeneous and sample representative of that?
 
matc said:
another question though....I ran the predicted beersmith numbers and came up with this..it seems impossible to get such a high OG with the pre boil gravity

predicted pre boil volume = 21 L,
predicted pre boil gravity = 1.052

(1.052-1)*21 = 1.092

predicted post boil volume = 17 L
predicted post boil gravity = 1.068

(1.068-1)*17 = 1.156

156-92 = 64 of difference. Maybe beersmith is totally wrong ???
Click to expand...

When I set Beersmith up for a 21 L (5.55 gal) pre-boil volume, 1.052 pre-boil SG, and 17 L (4.49 gal) post-boil volume, it predicts a post-boil SG of 1.064 (not 1.068)
21 * 0.052 = 1.092
17 * 0.064 = 1.088​
That error is within rounding error due to using only 3 digits for SG.

Brew on :mug:
 
Derek1985 said:
Your using liters. You need to use gallons with specific gravity.
Click to expand...

No you don't.
21 L * 0.264172 gal/L * pre-boil_SG = 17 L * 0.264172 gal/L * post-boil_SG
reduces to:​
21 L * pre-boil_SG = 17 L * post-boil_SG
​
It's basic algebra. The resulting units are different, but so what? You only have to work in gallons and pounds if you want to work with ppg. The basic sugar mass balance equation is valid no matter what units you use.

Brew on :mug:
 
Derek1985 said:
doug293cz said:
21 * 0.052 = 1.092
17 * 0.064 = 1.088​
/QUOTE]

Again, these shouldn't be taken separately. They are part of an equality:

PBG*preV=OG*postV

Also, gallons should be used with SG.

So:

(52*5.5)/4.2=68=1.068
Click to expand...
Appears you can't even convert from liters to gallons correctly.
21 L * 0.264172 gal/L = 5.547612
17 L * 0.264172 gal/L = 4.490924​
so that
1000 * (1.052 - 1) * 5.547612 / 4.490924 = 64.235
64.235 points/gal => 1.064235 SG, which rounds to 1.064​
Same numbers you get if you do the math in liters.
52 * 21 / 17 = 64.235​
Back to 8th grade for you. :goat:

Brew on :mug:
Click to expand...
 
doug293cz said:
Derek1985 said:
Appears you can't even convert from liters to gallons correctly.
21 L * 0.264172 gal/L = 5.547612
17 L * 0.264172 gal/L = 4.490924​
so that
1000 * (1.052 - 1) * 5.547612 / 4.490924 = 64.235
64.235 points/gal => 1.064235 SG, which rounds to 1.064​
Same numbers you get if you do the math in liters.
52 * 21 / 17 = 64.235​
Back to 8th grade for you. :goat:

Brew on :mug:
Click to expand...

I think I'm most offended by the goat. I always thought myself more of an Ox
Click to expand...
 
Derek1985 said:
Relax. His post boil volume was 16L.

21*.052/16=~1.068
Click to expand...

I used 17 because I was responding to the following post where the OP was questioning the Beersmith predictions. Therefore, I used the predicted numbers.

matc said:
another question though....I ran the predicted beersmith numbers and came up with this..it seems impossible to get such a high OG with the pre boil gravity

predicted pre boil volume = 21 L,
predicted pre boil gravity = 1.052

(1.052-1)*21 = 1.092

predicted post boil volume = 17 L
predicted post boil gravity = 1.068

(1.068-1)*17 = 1.156

156-92 = 64 of difference. Maybe beersmith is totally wrong ???
Click to expand...

I agree that if his post-boil was 16 L and the pre-boil measurements were correct, then he should have had:

1000 * (1.051 - 1) * 21 / 16 = 67. (In one of his posts he said his actual pre-boil was 0.051.

For the numbers to work, you have to use all actual or all predicted. Mixing them will get you confused.

Brew on :mug:
 
Someone assumed I measured my gravity at 46 C but I use Fahrenheit when brewing, so my sample was taken at 46F, which is cold and needs to be corrected slightly.

So with all that said Doug, I guess I should recheck my hydrometer reading with water at room temp and triple check my sight glass using boiling water ? When I calibrated it, I used tap water at like 70F I guess.
 
55x11 said:
Are you sure the pre-boil wort is well mixed up and you are not measuring some early runnings that are higher SG, as opposed to the average value for entire wort.

In other words, is your wort homogeneous and sample representative of that?
Click to expand...

OP, didn't see if you addressed this yet. IME this is a cause of discrepancy when the volumes are accurate.
 
Turns out I might have an issue with my volumes with beersmith. Under the equipment profile page, I verified the box "adjust mash volume for deadspace" was checked and it is. However, under the volume tab of my ipa recipe, the volumes for the mash and strike water does not add up to the preboil gravity. I think beersmith is not compensating for 1L of deadspace. What do you think ?

If my total water needed is 26L, I will lose 4L for grain absorption and 1L for deadspace which gives 21L of pre boil volume, not 22L as stated by beersmith !

Screen Shot 2015-07-31 at 10.51.08 AM.jpg
 
matc said:
Turns out I might have an issue with my volumes with beersmith. Under the equipment profile page, I verified the box "adjust mash volume for deadspace" was checked and it is. However, under the volume tab of my ipa recipe, the volumes for the mash and strike water does not add up to the preboil gravity. I think beersmith is not compensating for 1L of deadspace. What do you think ?

If my total water needed is 26L, I will lose 4L for grain absorption and 1L for deadspace which gives 21L of pre boil volume, not 22L as stated by beersmith !
Click to expand...

Wish I could help more. I don't use BeerSmith and am not familiar with it's inner workings like I am with my own spreadsheet.
 
matc said:
pre boil sg was 1.051 (temp was 46 but I corrected it with a chart)

.
Click to expand...


I assume your preboil temp was 146f, and not 46c or f.

Most prefer to cooling the hydro sample over using the correction chart, I'm not sure the chart is reliable for such a large correction.

As said, either your hydro numbers, and or volumes are flawed, or you spilled a lot of wort / sugar.
 
matc said:
Turns out I might have an issue with my volumes with beersmith. Under the equipment profile page, I verified the box "adjust mash volume for deadspace" was checked and it is. However, under the volume tab of my ipa recipe, the volumes for the mash and strike water does not add up to the preboil gravity. I think beersmith is not compensating for 1L of deadspace. What do you think ?

If my total water needed is 26L, I will lose 4L for grain absorption and 1L for deadspace which gives 21L of pre boil volume, not 22L as stated by beersmith !
Click to expand...


To explain original post, you are looking at ~16% difference. But your explanation of volume correction is about 0.5% difference.

Bottom line - you were either wrong in the measurements of gravity OR measurements of volumes. Or both.
 
yes I know, I don't know what happened with my og but for the moment, I'm trying to understand why Beersmith is short on 1 L after the mash. And yes I checked the box "adjust mash volume for deadspace"
 
There is a 1l loss for cooling shrinkage in the center section. It is probably that. Beersmith is probably assuming pre boil is measured hot, post boil is measured after cooling.
 
It looks like you've got things set so that all your measurements are being rounded to the nearest liter. For example, the 4% cooling should be .68 liter, it's marked as 1. I don't know what grain absorption is supposed to be in liter per kg, but I highly doubt it comes out to exactly 4 L on the dot. There must be a setting in options to have it go out more decimal places - I just tried changing the units to metric in my BS program and it goes out to .01 liter. Not sure if this is your issue but given that the cooling itself is rounded up about a third of a liter it might be.
 
Running some numbers I think this could be your issue. Look at the differences when rounding to a whole liter (grain absorption may not be accurate but illustrates the issue of rounding). If you add up the numbers in first column they match, in the second column you're now a liter off.

................................Actual .............Rounded

Mash water ................ 11 .................11
Grain absorption ...........3.55 ..............4
Avail from mash ...........7.45 ...............7
Deadspace ....................1 ..................1
Sparge vol .................15.23...............15
Boil volume ................21.68 ..............22
boil off .........................5 ..................5
cooling ........................0.68 ..............1
trub loss .......................2..................2
batch size ....................14.................14

Edit: sorry trying to format to read better and corrected some numbers
 
chickypad said:
It looks like you've got things set so that all your measurements are being rounded to the nearest liter. For example, the 4% cooling should be .68 liter, it's marked as 1. I don't know what grain absorption is supposed to be in liter per kg, but I highly doubt it comes out to exactly 4 L on the dot. There must be a setting in options to have it go out more decimal places - I just tried changing the units to metric in my BS program and it goes out to .01 liter. Not sure if this is your issue but given that the cooling itself is rounded up about a third of a liter it might be.
Click to expand...

chickypad said:
Running some numbers I think this could be your issue. Look at the differences when rounding to a whole liter (grain absorption may not be accurate but illustrates the issue of rounding). If you add up the numbers in first column they match, in the second column you're now a liter off.

................................Actual .............Rounded

Mash water ................ 11 .................11
Grain absorption ...........3.55 ..............4
Avail from mash ...........7.45 ...............7
Deadspace ....................1 ..................1
Sparge vol .................15.23...............15
Boil volume ................21.68 ..............22
boil off .........................5 ..................5
cooling ........................0.68 ..............1
trub loss .......................2..................2
batch size ....................14.................14

Edit: sorry trying to format to read better and corrected some numbers
Click to expand...
I think you may be on to something with the rounding errors, and reference temps for volume measurements. I was looking thru the Beersmith on-line help yesterday to see if there was any explanation of assumed temps for pre-boil or post-boil volume measurements, but couldn't find anything. Does anyone know for sure what temps Beersmith assumes?

Number of decimal places shown for volumes, weights, etc. can be set on the Options => Units menu, which is the same place you set what units you want to use (e.g. pounds or kilograms.)

:off: Note on getting things that require fixed spacing to line up (like columns.) If you use the "code" html tags, around the text where you want to maintain fixed spacing, then you won't get proportional fonts and collapse of consecutive spaces. As a result, you get this:

Code: 
Ingredients:
------------
Amt         Name                                      Type    %/IBU
4.08 kg     Pale Malt (2 Row) US (2.0 SRM)            Grain   83.7 %
0.45 kg     Caramel/Crystal Malt - 60L (60.0 SRM)     Grain   9.3 %
0.23 kg     Victory Malt (25.0 SRM)                   Grain   4.7 %
0.11 kg     Caramel/Crystal Malt -120L (120.0 SRM)    Grain   2.3 %
0.25 oz     Amarillo Gold [9.50 %] - First Wort 60.0  Hop     8.9 IBUs
0.53 oz     Amarillo Gold [9.50 %] - Boil 20.0 min    Hop     10.5 IBUs
0.53 oz     Amarillo Gold [9.50 %] - Boil 10.0 min    Hop     6.3 IBUs
0.74 oz     Amarillo Gold [9.50 %] - Boil 5.0 min     Hop     4.8 IBUs
0.74 oz     Amarillo Gold [9.50 %] - Steep/Whirlpool  Hop     4.4 IBUs
1.0 pkg     American Ale II (Wyeast Labs #1272)       Yeast   -

Instead of this:
Ingredients:
------------
Amt Name Type %/IBU
4.08 kg Pale Malt (2 Row) US (2.0 SRM) Grain 83.7 %
0.45 kg Caramel/Crystal Malt - 60L (60.0 SRM) Grain 9.3 %
0.23 kg Victory Malt (25.0 SRM) Grain 4.7 %
0.11 kg Caramel/Crystal Malt -120L (120.0 SRM) Grain 2.3 %
0.25 oz Amarillo Gold [9.50 %] - First Wort 60.0 Hop 8.9 IBUs
0.53 oz Amarillo Gold [9.50 %] - Boil 20.0 min Hop 10.5 IBUs
0.53 oz Amarillo Gold [9.50 %] - Boil 10.0 min Hop 6.3 IBUs
0.74 oz Amarillo Gold [9.50 %] - Boil 5.0 min Hop 4.8 IBUs
0.74 oz Amarillo Gold [9.50 %] - Steep/Whirlpool Hop 4.4 IBUs
1.0 pkg American Ale II (Wyeast Labs #1272) Yeast -​

This is what code tags look like in your reply edit window:

Code tag example.png

You can insert "code" tags with a button at the top of the reply window:

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Brew on :mug:
 

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