Author Topic: Can't understand where pre-boil gravity value comes from  (Read 261 times)

Offline jpm28

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Can't understand where pre-boil gravity value comes from
« on: March 23, 2020, 11:16:58 AM »
I just started using BeerSmith and I have already made my first recipe. However, there are some gravity values than I can't understand where they come from.
How can pre-boil gravity be higher than post-boil? :/ I'm afraid I set up something wrong, but everything seems ok.

◯ Add water to achieve boil volume of 5,00 L
◯ Estimated pre-boil gravity is 1,059 SG
  --
◯ Estimated Post Boil Vol: 3,50 L and Est Post Boil Gravity: 1,044 SG
◯ Add water if needed to achieve final volume of 6,50 L

Is pre-boil gravity not taking into account the top-up water to the kettle? (in this case 1,5L to make a total of 5L).
Even though, I made the calculations and doesn't make sense:

C0 x V0 = Cf x Vf doesn't apply. [59 x 5 != 44 x 6,5] --> 295 != 286

Thanks for your time!

J.

Offline Oginme

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Re: Can't understand where pre-boil gravity value comes from
« Reply #1 on: March 23, 2020, 11:44:00 AM »
Are you adding any dilution water following the boil? 

If not, I would suspect that one of your gravity readings is incorrect.  I am assuming that the readings were taken at or near the calibration temperature of the hydrometer or at the very least corrected for the temperature.  Beyond those common issues, I would suspect a sample was not mixed well enough to make it homogenous and representative of the wort.

If I ran into readings like this, I would take the one reading I had the most faith in and use that.   Ignore the rest and use the next brew to dial in your system.
Recycle your grains, feed them to a goat!

Offline jpm28

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Re: Can't understand where pre-boil gravity value comes from
« Reply #2 on: March 23, 2020, 01:18:03 PM »
Are you adding any dilution water following the boil? 

If not, I would suspect that one of your gravity readings is incorrect.  I am assuming that the readings were taken at or near the calibration temperature of the hydrometer or at the very least corrected for the temperature.  Beyond those common issues, I would suspect a sample was not mixed well enough to make it homogenous and representative of the wort.

If I ran into readings like this, I would take the one reading I had the most faith in and use that.   Ignore the rest and use the next brew to dial in your system.

Woops, forgot to say! These are estimations from the program, I haven't brewed this recipe yet (not at least following the BeerSmith steps).
That's why I think I misconfigured something in BeerSmith, its estimations make no sense...

Thanks Oginme!
« Last Edit: March 23, 2020, 01:29:20 PM by jpm28 »

Offline Oginme

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Re: Can't understand where pre-boil gravity value comes from
« Reply #3 on: March 23, 2020, 01:38:17 PM »


Is pre-boil gravity not taking into account the top-up water to the kettle? (in this case 1,5L to make a total of 5L).
Even though, I made the calculations and doesn't make sense:

C0 x V0 = Cf x Vf doesn't apply. [59 x 5 != 44 x 6,5] --> 295 != 286



OK, I think I understand.  If 5 liters is your pre-boil volume, then where do you get the 6.5 liters of finished volume.  Is this a beer, wine, or mead?  Your final volume does not take into account process losses when doing the sugar point balance, so if you have any losses to trub or chilling, this volume also includes sugar which is lot in the system.

The way the software works is by starting with your batch size (amount into fermenter) and then working the volumes back based upon the process losses (trub loss, boil off, mash tun dead space, grain absorption) to the total water needed for the batch.  It will subtract water additions which are in the equipment profile to give you the initial water requirements.  Along the way, it notes the volumes needed at each step.  This can be clearly seen on the 'vols' tab of a recipe.

Now for the sugar balance, the program takes the total or brew house efficiency from the equipment profile and uses that value times the potential sugar found in the grain bill to give you the amount of sugar in the fermenter.  This number divided by the fermenter volume (batch size) will give you the gravity readings.  It will then work backwards from the fermenter (again) calculating how much sugar is contained in each process loss based upon the equipment profile.  Then it takes that amount of sugar and assumes that it gets extracted from the grist, giving you your mash efficiency.

I hope this helps with figuring out why your profile is giving you the gravity numbers you listed.
Recycle your grains, feed them to a goat!

Offline jpm28

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Re: Can't understand where pre-boil gravity value comes from
« Reply #4 on: March 23, 2020, 01:49:42 PM »


Is pre-boil gravity not taking into account the top-up water to the kettle? (in this case 1,5L to make a total of 5L).
Even though, I made the calculations and doesn't make sense:

C0 x V0 = Cf x Vf doesn't apply. [59 x 5 != 44 x 6,5] --> 295 != 286



OK, I think I understand.  If 5 liters is your pre-boil volume, then where do you get the 6.5 liters of finished volume.  Is this a beer, wine, or mead?  Your final volume does not take into account process losses when doing the sugar point balance, so if you have any losses to trub or chilling, this volume also includes sugar which is lot in the system.

The way the software works is by starting with your batch size (amount into fermenter) and then working the volumes back based upon the process losses (trub loss, boil off, mash tun dead space, grain absorption) to the total water needed for the batch.  It will subtract water additions which are in the equipment profile to give you the initial water requirements.  Along the way, it notes the volumes needed at each step.  This can be clearly seen on the 'vols' tab of a recipe.

Now for the sugar balance, the program takes the total or brew house efficiency from the equipment profile and uses that value times the potential sugar found in the grain bill to give you the amount of sugar in the fermenter.  This number divided by the fermenter volume (batch size) will give you the gravity readings.  It will then work backwards from the fermenter (again) calculating how much sugar is contained in each process loss based upon the equipment profile.  Then it takes that amount of sugar and assumes that it gets extracted from the grist, giving you your mash efficiency.

I hope this helps with figuring out why your profile is giving you the gravity numbers you listed.

It's a beer  ;D

My pot can only boil 5L (and even that volume is on the edge already). My idea is to have a very dense wort and then dilute it to the desired OG (in this case 1,044) by topping up up to 6,5L with water which will go to the fermentor. That way I can have the largest batch possible given my humble equipment.
What I don't understand is how can pre-boil estimated gravity be higher than the post-boil estimated gravity...I will check the calculation flow of the program and try to see where it goes wrong...
« Last Edit: March 23, 2020, 01:51:53 PM by jpm28 »

Offline BOB357

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Re: Can't understand where pre-boil gravity value comes from
« Reply #5 on: March 23, 2020, 03:29:54 PM »
Pre boil and post boil gravities are estimated based, primarily, on your inputs. Find the erroneous input(s) and you'll find the problem. Exporting the recipe and posting it will give us all the information we need to find the problem if you're unable to.
Bob

Offline Oginme

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Re: Can't understand where pre-boil gravity value comes from
« Reply #6 on: March 23, 2020, 04:49:45 PM »
If you want another set of eyes to look at it, then export the recipe as a .bsmx file by clicking on 'file' > 'export selected' and then saving the recipe in the beersmith recipe extension.  That way we can help guide you through the set up and see what your concern is.  My guess is that the 'post boil gravity' is really your gravity into the fermenter and therefore includes your top off water.

Recycle your grains, feed them to a goat!

Offline jpm28

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Re: Can't understand where pre-boil gravity value comes from
« Reply #7 on: March 23, 2020, 05:15:19 PM »
Pre boil and post boil gravities are estimated based, primarily, on your inputs. Find the erroneous input(s) and you'll find the problem. Exporting the recipe and posting it will give us all the information we need to find the problem if you're unable to.

If you want another set of eyes to look at it, then export the recipe as a .bsmx file by clicking on 'file' > 'export selected' and then saving the recipe in the beersmith recipe extension.  That way we can help guide you through the set up and see what your concern is.  My guess is that the 'post boil gravity' is really your gravity into the fermenter and therefore includes your top off water.



Here it goes, I hope these are helpful.

Thanks for your help guys!

Offline Oginme

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Re: Can't understand where pre-boil gravity value comes from
« Reply #8 on: March 24, 2020, 07:41:05 AM »
OK, so you are actually topping off with 3+ liters after the boil to get to your final volume in the fermenter.  If you take out this top off water, you are ending up with 3.5 liters at the  end of the boil.  This volume with cooling shrinkage will give you 3.36 liters (cold volume) at the end of the boil with a projected gravity 1.090.  You lose 0.2 liters to trub, so your actual top off to get to your target batch size of 6.5 liters is 6.5 - 3.16 = 3.34 liters.  So from a straight dilution you have 90 gravity points * 3.16 liters / 6.5 liters = 44 gravity points or a gravity reading of 1.044. 

Note that as you follow the volumes back up from the batch size on the vols tab, you can see the volume calculation unfold.

If it were my process, I would contemplate making the following change: You are mashing and sparging (method?) to get 5 liters pre-boil in your 6.5 liter kettle.  I would increase the sparge (decrease the fermenter top off) to obtain around 5.5 to 6 liters.  Using this additional sparge water will improve your mash efficiency and you will end up with less water you need to top off.  If you are concerned with boil over, try to get some Fermcap S or similar food grade defoamer to help limit the foam generation at the beginning of the boil.

Otherwise, your equipment profile is doing what you expect it to do.  Since BeerSmith does not give you a final post boil gravity, but instead gives you the gravity of the wort in the fermenter, you may need to play with the numbers temporarily to get your desired target for end of the boil volume.  You can do this by zeroing out your fermenter top off and the lowering your batch size by that same volume.  This will give you a reasonable estimate of post boil volume.  You can note this on the notes tab and then either exit out without saving or reverse the changes to get back to your original profile.

Recycle your grains, feed them to a goat!

Offline jpm28

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Re: Can't understand where pre-boil gravity value comes from
« Reply #9 on: March 24, 2020, 09:03:45 AM »
OK, so you are actually topping off with 3+ liters after the boil to get to your final volume in the fermenter.  If you take out this top off water, you are ending up with 3.5 liters at the  end of the boil.  This volume with cooling shrinkage will give you 3.36 liters (cold volume) at the end of the boil with a projected gravity 1.090.  You lose 0.2 liters to trub, so your actual top off to get to your target batch size of 6.5 liters is 6.5 - 3.16 = 3.34 liters.  So from a straight dilution you have 90 gravity points * 3.16 liters / 6.5 liters = 44 gravity points or a gravity reading of 1.044. 

Oh! I understand now! There were a lot of losses I was not taking into account here...Thanks a lot! ;D

If it were my process, I would contemplate making the following change: You are mashing and sparging (method?) to get 5 liters pre-boil in your 6.5 liter kettle.  I would increase the sparge (decrease the fermenter top off) to obtain around 5.5 to 6 liters.  Using this additional sparge water will improve your mash efficiency and you will end up with less water you need to top off.  If you are concerned with boil over, try to get some Fermcap S or similar food grade defoamer to help limit the foam generation at the beginning of the boil.

Actually I already changed that! You are so right, it's my fourth batch ever and only now after reading more I discovered why I had such a low efficiency...Now I changed it so it has a 1:1.5 ratio of mash:sparge water. I have a question though: for 2,61L of strike water, I would need to warm it to 75,6?C(=168,08?F) which is quite close to the enzymes limit according to what I read. I know temperature of water will inmediately decrease as I add the grain, but I don't know if that first shock will be harmful for the enzyme activity. Am I wrong to worry?

Otherwise, your equipment profile is doing what you expect it to do.  Since BeerSmith does not give you a final post boil gravity, but instead gives you the gravity of the wort in the fermenter, you may need to play with the numbers temporarily to get your desired target for end of the boil volume.  You can do this by zeroing out your fermenter top off and the lowering your batch size by that same volume.  This will give you a reasonable estimate of post boil volume.  You can note this on the notes tab and then either exit out without saving or reverse the changes to get back to your original profile.
Thanks for the tip, noted for the future!

Thanks again for your support! Not much to do these days apart from playing guitar and drinking home-brewed beer...hopefully I'll get out of this having a solid knowledge of brewing and jazz ha!

J.

Offline Oginme

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Re: Can't understand where pre-boil gravity value comes from
« Reply #10 on: March 24, 2020, 09:11:25 AM »


 I have a question though: for 2,61L of strike water, I would need to warm it to 75,6?C(=168,08?F) which is quite close to the enzymes limit according to what I read. I know temperature of water will inmediately decrease as I add the grain, but I don't know if that first shock will be harmful for the enzyme activity. Am I wrong to worry?



You will lose a very little of the active enzymes.  First, in order to be denatured by temperature they need to be in solution.  They do not automatically solubilize when you add the grains to the water, so by the time they start unfolding and are active, you temperature will be well below where they would be greatly affected. 
Recycle your grains, feed them to a goat!

Offline jpm28

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Re: Can't understand where pre-boil gravity value comes from
« Reply #11 on: March 24, 2020, 09:36:08 AM »


 I have a question though: for 2,61L of strike water, I would need to warm it to 75,6?C(=168,08?F) which is quite close to the enzymes limit according to what I read. I know temperature of water will inmediately decrease as I add the grain, but I don't know if that first shock will be harmful for the enzyme activity. Am I wrong to worry?



You will lose a very little of the active enzymes.  First, in order to be denatured by temperature they need to be in solution.  They do not automatically solubilize when you add the grains to the water, so by the time they start unfolding and are active, you temperature will be well below where they would be greatly affected.

Ok then! Recipe variables are settled. Let's see how it turns out.
Thank you very much!
J.

 

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