Beersmith volumes

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Beersmith volumes

Unread postby Nesto » Mon Sep 29, 2014 9:39 pm

Pulling this out from another thread...
Luis Coentrao wrote:I recently made my first No-Sparge BM Mash (thanks to Nesto and all the folks), just loved it.

I also use Beersmith for a while. I use a batch size of 20L and Brewhouse efficiency 77%.
I regularly reach mash efficiencies (in Beersmith software) 85%. My pre-boil data is quite the same as stated in Beersmith (SG and volume). However, what I found is a 2-3 gravity points lower OG in comparison with Beersmith data, with equal post-boil volumes and batch sizes. The only way to get a similar data is to delete the cool shrinkage number (4% to 0%, in liters 1L to 0L) and to increase the trub loss for about 1L (from 2L to 3L). With these data, the difference between pre-boil SG and OG is the same in Beersmith and real-life.

Other thing, the Beersmith pre-boil volume takes into account the mash temperature (78C)?

Luis, your problem is familiar and I found this a few months ago...

But I realized a few weeks ago, when Luis mentioned something similar, that I really didn't understand what was being said in the thread from the Beersmith forum. I think I finally understand what BeerSmith is doing! The 4% increase is built into pre-boil volumes - you can see it on the volumes tab in a recipe - so that volume will match what you expect as the boil begins. The 4% isn't in the Mash section, only the boil section to calculate post-boil volume. That's not a huge deal for me, I have a calculator in the brewing spreadsheet that I use to back out the volume I need before heating the water up. And then when I measure at mash out temp (77C) when I'm getting ready to boil, there is only a 1% difference from 77C to 100C in apparent volume.

But what's leading to your problem of losing 2-3 points of gravity is that it appears Beersmith is also adding that extra 4% to your gravity calculation as water, which it isn't. So if you hit your Beersmith calculated pre-boil gravity, that means you will miss your Beersmith calculated post-boil gravity. This is what users g8tors and brewfun in the referenced Beersmith forum thread found...

The equation should be: (pre-boil vol)(pre-boil Gravity Units) = (post boil vol)(post boil Gravity Units)

... but in Beersmith, the equation used is: (pre-boil vol)(pre-boil GU) = (post boil vol)(.96)(post boil GU)

Another way to look at it is the first equation assumes all measurements are made at the same temperature - probably 100C. For the 2nd equation to be accurate, you'd need to measure pre-boil volume at 22C and post-boil volume at 100C.

I haven't seen confirmation of this from Brad, but it fits with the formulas. I haven't figured out how to account for this in my recipe design yet - or even IF I should. I mean, I can miss by 3 points for many other reasons ;)
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Re: Beersmith volumes

Unread postby Luis Coentrao » Tue Sep 30, 2014 10:46 pm


Great thread!!

My last Brew numbers,
- Beersmith data: pre-boil SG 1.049, pre-boil Vol. 26.5L, post-boil SG 1.059, post-boil Vol. 23L, Batch size 20L
- My data: pre-boil SG 1.050, pre-boil Vol. (80C) 26.5L, post-boil SG 1.057, post-boil Vol. 23L, Batch size 20L

My pre-boil Vol. of 26.5L was measured at 80C. To get the "real" volume we should multiply to 0.97.

If we use Beersmith equation: 26.5 X 97 X 50 = post-boil SG X 23 X 0.96,
Post-boil SG=1.058. I think that's it.
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