Author Topic: Calculating gravity on partial mash and extract batches incorrectly?  (Read 1838 times)

Offline h22lude

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Re: Calculating gravity on partial mash and extract batches incorrectly?
« Reply #15 on: October 19, 2019, 07:40:09 PM »
The steeping grains portion of my issue has been solved.  I needed to adjust the steeping efficiency and the grain potential to get what I wanted.  I'm ok with that.  My issue now is if I have an extract addition in an all grain batch.  So I have base malt and will be mashing.  I need to use the all grain or partial mash setting.  This is where I don't think it calculates extract additions properly.  For a TL:DR, read the last paragraph from my last post.

Online Oginme

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Re: Calculating gravity on partial mash and extract batches incorrectly?
« Reply #16 on: October 20, 2019, 06:37:20 AM »
OK, got it.  To best understand what is going on with your equipment profile and recipe I recommend exporting it as a .bsmx file and posting it here.  That way we can see how your profiles and recipe interact to determine if the calculations are what should be expected and where they may be going off for you.
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Offline h22lude

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Re: Calculating gravity on partial mash and extract batches incorrectly?
« Reply #17 on: October 20, 2019, 07:30:35 AM »
There was a lot of changing things to figure this out so it will be hard to post all of it.  I posted my equipment profile.  Recipe extract is just 5lbs DME with extract setting.  REcipe partial mash is just 5lbs DME with partial mash setting showing that the gravity changes.  Recipe partial mash grain only is with just 8lbs pilsner showing the gravity for just the grain.  Recipe partial mash grain and extract is showing the grain plus adding DME to show that is still calculates the extract addition at into the fermentor volume.

Online Oginme

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Re: Calculating gravity on partial mash and extract batches incorrectly?
« Reply #18 on: October 20, 2019, 11:42:34 AM »
OK, so the only meaningful one is the recipe in question:  Partial mash grain and extract. 

Important info from recipe:

BHE: 72%

Batch size:  5.5 gal
Trub loss: 1 gal

Grain:  8 lbs Pilsner at 1.036 contribution
Extract: 5 lbs DME at 1.045 contribution

Given your BHE and grain bill, you have 8 lbs at 36 points for 288 gravity points of grain. 
At 72% BHE, there are 207 gravity points in the fermenter
Per gallon, this is 207/5.5 = 38 gravity points per gallon.
With one gallon of trub, there would be 38 points lost to the trub from the contribution of the grain.
That means that 207 points plus 38 points, or 245 gravity points are in the post boil volume.

Your extract will give you 5 lbs at 45 points for 225 gravity points.

If the extract is added to the boil, then 100% of this is in the post boil volume.
This contribution of 225 points plus the grain contribution of 245 points gives you 470 gravity points post boil
Your post boil volume is 5.5 gal in fermenter plus 1 gal trub loss or 6.5 gallons

470 gravity points in 6.5 gallons is 72 gravity points per gallon or a target of 1.072 target final gravity

Since this does not match BeerSmith's prediction, we will tackle it another way:

245 points from the grain in 6.5 gallons gives a gravity point contribution of 38 gravity points per gallon
225 points from the extract in the fermenter volume of 5.5 gallons gives us 41 gravity points per gallon.

This total is 79 gravity points or an OG of 1.079, which does match BeerSmith's prediction

So it appears you are correct in your assertion that the program does not calculate this value correctly.  The best thing to do at this point is to copy this to Brad so that he can look at the way the program calculates out the OG value for partial mash.  He has commented that he is working on some fixes right now for a update of the current version of BeerSmith (which does do the calculation the same was as BS2), so this would be the best time to let him know of the issue.

This is why attaching a recipe demonstrating your issue is critical to verification or helping to understand BeerSmith.
« Last Edit: October 20, 2019, 11:44:45 AM by Oginme »
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Offline h22lude

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Re: Calculating gravity on partial mash and extract batches incorrectly?
« Reply #19 on: October 20, 2019, 03:22:11 PM »
I emailed him via the support page and linked this thread for more detail.  Thanks for staying with me on this, confirming my assumption and helping me talk through it.

Offline h22lude

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Re: Calculating gravity on partial mash and extract batches incorrectly?
« Reply #20 on: October 20, 2019, 03:23:32 PM »
This would be funny if it weren't so pathetic. You actually believe that you're right and everyone else is screwed up, don't you? Have fun with yourself.

Just in case you wanted an update.  It has been confirmed BS is calculating extract additions incorrectly for all-grain and partial grain, just as I suspected.  Cheers mate
« Last Edit: October 20, 2019, 03:55:39 PM by h22lude »

Offline GigaFemto

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Re: Calculating gravity on partial mash and extract batches incorrectly?
« Reply #21 on: October 20, 2019, 06:19:31 PM »
That's what I said in the second reply to you. I guess I wasn't clear enough. You seem to be mathematically adept enough to do the calculations for yourself, so now that you know that BeerSmith is wrong, just do it yourself. I wrote an Excel spreadsheet that I use when I know I will be using a lot of extract. It's not that hard.

--GF

Offline h22lude

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Re: Calculating gravity on partial mash and extract batches incorrectly?
« Reply #22 on: October 21, 2019, 04:46:33 AM »
That's what I said in the second reply to you. I guess I wasn't clear enough. You seem to be mathematically adept enough to do the calculations for yourself, so now that you know that BeerSmith is wrong, just do it yourself. I wrote an Excel spreadsheet that I use when I know I will be using a lot of extract. It's not that hard.

--GF

That's fine, I can do it myself but shouldn't I want a paid for program to be fixed?

 

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