Author Topic: What settings change gravity gain post boil? Mine dont match beersmith  (Read 5794 times)

Offline Truman48

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Hi gents, Ive been using beersmith for many years now and have all of my parameters setup really well. However I always seem to have the problem where the gravity points gained Post boil are always a lot higher in Beersmith compared to my actual.
For example most of my recipes for a 60 minute boil I will gain around 4 points, but Beersmith says around 8 points. For a 90 min boil I get 7 points, Beersmith says 11 points.
using the formula SG = pre boil volume * pre boil litres/post boil litres matches up with what I actually get and not what Beersmith says.

But I cant find anything wrong with my settings.  3 litre an hour Evap rate is spot on. Preboil volume and post boil volume are always spot on with beersmith too.

Any ideas what else I can look at here?

Offline Truman48

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Re: What settings change gravity gain post boil? Mine dont match beersmith
« Reply #1 on: February 14, 2018, 03:14:41 AM »
Is anyone actually on these forums???

Offline Oginme

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Re: What settings change gravity gain post boil? Mine dont match beersmith
« Reply #2 on: February 14, 2018, 05:21:27 AM »
People are here.  From the information given, it is difficult to give some specific advice.  Export a recipe you have brewed as a .bsmx file with the sessions tab filled out with your measured results and maybe we can give you some more directed areas to look into.
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Offline Truman48

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Re: What settings change gravity gain post boil? Mine dont match beersmith
« Reply #3 on: February 15, 2018, 01:14:11 AM »
Thanks for the reply Oginme. Here is one of my last brews that shows exactly what Im talking about. The Beersmith gravity points gain should be 7 points, but I only managed a 4 point gain.

Offline Oginme

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Re: What settings change gravity gain post boil? Mine dont match beersmith
« Reply #4 on: February 15, 2018, 07:11:00 AM »
OK, let's make sure I am reading this correctly and you can guide me if I am off anywhere.

You are collecting 29 liters of wort at 1.044 gravity.  I am assuming that you are measuring the gravity at standard conditions set by your hydrometer (calibration temperature).

29 liters of hot wort would equate to approximately 27.9 liters with the 4% shrinkage factor.  (I do this because the ending volumes are, I am assuming again, taken at cool conditions so I want to put the volume on an equal basis with your ending volume).

You have 2 liters of trub -- was this measured or from the initial equipment profile? 

23 liters were added to the carboy or fermentation container at a gravity of 1.048. 

So if I follow the gravity points using these numbers, I will get:

Pre-boil:  27.9 liters at 44 gravity points = 1228 points

Post boil: 23 liters + 2 liters trub at 47 points = 1200 points or about  ~ 2% off of predicted.

At initial glance, you boil off rate seems to be correct, which leads us to other possible areas of error.

How accurately can you measure your volumes?  If you can only really measure to the nearest .5 liters, then your error band in measurement is around 1.7%.  That error applies to every volumetric reading you take, though for each piece of equipment the degree of error may be lower or higher. 

My first instinct when looking at your process and results would be to make sure you are getting good measurements on your volumes: measure your actual trub loss and make sure your volumetric markings are accurate for your kettle and fermenter.  If the volume indicators are pre-printed or engraved on the kettle, I would be very suspicious of the accuracy (but then again, I used to work as a process engineer, so I am suspicious of most measurements unless I take them myself).

Start there and post results!  We'd like to help you get this as accurate as you can make it.



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Offline Truman48

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Re: What settings change gravity gain post boil? Mine dont match beersmith
« Reply #5 on: February 16, 2018, 01:23:02 AM »
Quote
You are collecting 29 liters of wort at 1.044 gravity.  I am assuming that you are measuring the gravity at standard conditions set by your hydrometer (calibration temperature).
Yes thats correct. using a refractometer thats been calibrated and tested and wort temp is cooled to around 20C.

Quote
You have 2 liters of trub -- was this measured or from the initial equipment profile? 

23 liters were added to the carboy or fermentation container at a gravity of 1.048. 
(/quote]
Ok here is where things get a bit confusing. I dont really measure what goes into the fermenter or what my trub is. Although I have measured the trub in the past a few times and it was always around 2 litres but if its a low hopped beer it might be 1.5 litres, and a IPA might be 2.5 or 3 litres. My EOB volume was 26 litres and gravity was 1.048. I didn't think it mattered what then went into the fermenter as I thought the gravity points is worked out from pre boil and post boil volumes regardless of what goes into the fermenter?? But it would have been around 24 litres in the fermenter.

My measurements were done with a fairly expensive and accurate measuring jug and double checked a few times. (I did it once on my old urn using a cheap $2 shop jug and it was way out so this time I made sure I used a decent jug.
My boil off rate has been checked a number of times and is correct.

Any ideas?

Offline Oginme

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Re: What settings change gravity gain post boil? Mine dont match beersmith
« Reply #6 on: February 16, 2018, 05:48:38 AM »
Your refractometer is calibrated with water? against a hydrometer? Are you reading directly in specific gravity or in Brix and converting?

I take it you measured your post boil volume while still hot?  Or is it a cold volume reading? 

While I measure my EOB volume hot, I always rely on volume into fermenter and trub volume to do my final calculations as they are much more precise in my system.  Where these measurement do count is if you depend upon BeerSmith's calculation of actual efficiency to fine tune your process. 

One of the flaws in BeerSmith is the use of volumes at the thermally expanded values for doing efficiency calculations.  All volumes need to be at a standardized temperature in order to complete the balance with any accuracy.  The reason this is important is if your EOB volume is measured cold, then your actual boil off rate is 29 liters - 26 liters*1.04 (thermal expansion) = ~2 liters.  Even this will be a little off, because the thermal expansion of water at 150F is around 1.3% versus at boiling where it is 4% and the program does not scale the volumes based upon temperature. 

If you are using hot volume pre-boil to hot post boil, you are good with the boil off volume and the volumes through your system make sense.  With this being most likely true, I would suspect that your refractometer readings are off just a bit.  I usually take around 3 to 5 samples from a stirred kettle to get consistent results with my refractometer as with the sample size being so small it is easy to get a small error.

I would also recommend taking a final gravity reading with a hydrometer and comparing that to your refractometer for a few brews until you become confident in your refractometer reading.  If you have not done a correction calibration for your refractometer in BeerSmith, I would highly recommend it.  Then you can take your readings in Brix and use the refractometer tool to correctly convert to specific gravity. 

Recycle your grains, feed them to a goat!

Offline Truman48

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Re: What settings change gravity gain post boil? Mine dont match beersmith
« Reply #7 on: February 18, 2018, 04:23:53 AM »
Yes my refractometer was calibrated in water.  I tested it again today and did a brew where I measured my pre boil wort with my refractometer and it was 1.044 and then my hydrometer which was also 1.044. This is with the sample cooled to 20 C.

My post boil volume is whilst still hot as I usually run it through a plate chiller into the fermenter.

Ive just done a small batch brew in my 12 litre pot (I normally brew on my 3V system). BS said SOB volume was 8.8 litres and 1.050, I got 8.8 litres and 1.044.
BS says EOB should be 6.8 litres and 1.067. I got 7 litres (measured at flame out so 100C wort) and only 1.056. Still waiting for the sample to cool so I can double check it on my hydro as well. So even if I let this cool Im assuming Ill have a similar EOB volume of 6.8 as BS says. But my gravity is out by 9 points and I cant work out why that would be?

Ok so wort is now 40C and my volume is 6.6 litres. so 400mls less than at 100C. Checked the EOB gravity with my sample at 20C and it was 1.056 same as my refractometer which at least proves that my refractometer is accurate.

I just transferred 5 litres to the Demi John and had 1.5 litres of wort left over when I poured it into a jug to check. So I suppose final cooled volume was 6.5 litres. So should I change my boil off rate in beersmith to 8.8 litres - 6.5 litres = 2.3 litres an hour?

Offline Oginme

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Re: What settings change gravity gain post boil? Mine dont match beersmith
« Reply #8 on: February 18, 2018, 06:15:34 AM »
No, don't change your boil off rate based upon your cooled volume.  If you measured 7 liters at end of boil (hot), then your boil off rate for your small batch was 8.8 - 7 = 1.8 liters for the time of your boil.

Since you achieved the correct volume from your mash, but lower gravity reading, you need to adjust your brew house (total) efficiency.  When you plug in your final values into the program, BeerSmith will give you an actual efficiency reading on the 'sessions' tab.  When you plug in your volume to fermenter and adjust your trub loss for the extra volume you have left over, then the program should recalculate the brew house efficiency according to your actual values.  Do this for a few brews and you will gradually dial the program in to give you better predictions for your 12 liter system.

This same equipment profile will be different from your 3V set up. Here, since you posted your EOB volume hot, your boil off value is correct.  You seem to have the volumes down correctly, so I would think that any remaining deviation may be due to your efficiency being off.  Here you will need to follow the same process as you just did for your 12 liter system.

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Offline Truman48

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Re: What settings change gravity gain post boil? Mine dont match beersmith
« Reply #9 on: February 19, 2018, 01:09:40 AM »
Heres a screen shot of my session data from this last brew. (BIAB small batch) My efficiency was set to 70% but according to BS I only got 58.7%. I cant work out why its so low as I usually get at least 75% when doing BIAB years and years ago.

My 3V gives me around 65% efficiency and you can see from the screen shot the last brew I actually got 69% but the gravity gain was still lower than BS=7 points actual= 4 points.

im still lost as to whats going on. 

Thanks for all your help on this

Offline Oginme

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Re: What settings change gravity gain post boil? Mine dont match beersmith
« Reply #10 on: February 19, 2018, 05:33:14 AM »
OK, let's take them one at a time.

For you BIAB system, your volumes are measured and match the estimated volumes, so the issue is strictly with your mash extraction.  This is a matter of matching the calculated brew house efficiency so that the program will use your actual extraction rate versus what you told it when you set up your equipment profile.

For your 3V system, I must have missed something before, but you are targeting 23 liters in your fermenter but putting in 26 liters.  This added dilution masks the extra sugars you are pulling from your mash which is why you are seeing higher total efficiency.  Here, you need to (a) get a better measurement of what is going into your fermenter and (b) make sure your measurement on trub is correct.  While we have been looking at your measurement of EOB volume, BeerSmith does not use this value (as there is no place to enter it) but uses the fermenter volume and the estimated trub and chiller loss you provided in your equipment profile to calculate ending volumes.  While you may get a hot volume at the end of the boil which seems to match the BeerSmith prediction on the 'volumes' tab, if your ending (cold) volumes do not add up, it will throw off the calculation.  It would appear that you are also extracting more sugars (hence the higher brew house efficiency calculation) than planned.

The first thing to do is make sure you can accurately measure the volumes I cited above and get this straightened out.   This will change your brew house efficiency, most likely to match what the calculation is giving you now or close to it.

By the way, if you are getting 26 liters into your fermenter and 2 liters of trub, then your beginning of boil volume reading cannot be correct unless you are adding some water to top off elsewhere in your process.

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Offline Truman48

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Re: What settings change gravity gain post boil? Mine dont match beersmith
« Reply #11 on: February 19, 2018, 07:09:06 PM »
Ok so with my BIAB your saying I should drop my brewhouse efficiency down to around 58% for my next brew and see how the numbers go? 
I just don?t get why I?m getting such low numbers. I do sparge and rinse the grains into a strainer. Maybe I should do a full volume mash and not worry about sparging?

As for my 3V you might have just solved the issue. My figure of 26 litres into my fermenter is my EOB volume. I was using this as my into fermenter figure because I thought BeerSmith took off the Trub figure and then did it?s calculations.  I?m not 100% sure to be honest but realise now that?s where I?m stuffing up.  But I have measured my Trub a few times and it is always around 2 litres so I?m getting about 24 litres into the fermenter. I think this changes my efficiency to 64.5%.

Offline Oginme

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Re: What settings change gravity gain post boil? Mine dont match beersmith
« Reply #12 on: February 20, 2018, 07:27:53 AM »
For BIAB, the efficiency is almost always related to the crush.  You can crush your grains a lot finer since you do not have to worry about having a stuck sparge.  I was getting into the 90's for mash efficiency when I first got my grain mill and backed it off to the mid-80's to get better consistency, body, and color in my recipes.

The other property to chase after the crush is the mash pH.  Getting the mash pH into the 5.2 to 5.6 range will improve the enzyme performance and speed up the conversion of the starches to sugars.  This would apply to either of your systems.

Edit:  I find the difference between doing full volume BIAB and performing a sparge is only a couple of points of efficiency.  Given the time and effort involved, the majority of my BIAB brews are full volume and I only do a sparge when making high gravity recipes.
« Last Edit: February 20, 2018, 09:02:44 AM by Oginme »
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Offline Truman48

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Re: What settings change gravity gain post boil? Mine dont match beersmith
« Reply #13 on: February 21, 2018, 08:15:26 AM »
Yeah well I must admit my mill gap is set bigger due to the recirculation problems I have on my 3V even if I use rice hulls,. I didn?t bother to change it for my BIAB. 

But it?s probably increased a bit over the last year or 2 so might have to re check it.

Thanks for the help. 

Offline Truman48

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Re: What settings change gravity gain post boil? Mine dont match beersmith
« Reply #14 on: March 11, 2018, 05:53:34 AM »
Well Ive done 2 brews using my 18 litre urn and had some interesting results.

Scotch Ale set at 70% efficiency

Beer Smith SOB=16 litres 1.056. EOB 13 litres 1.072. 16 point increase 3 litres lost

Actual. SOB 16 litres 1.055 EOB 12 litres 1.070 15 point increase but lost 4 litres in the boil

So on my next brew I dropped the efficiency to 68% and increased the evaporation rate to 4 litres an hour. Results were as follows

Beersmith SOB 17.5 litres 1.051. EOB 13.5 litres and 1.071. 20 point gain

Actual was SOB 17.5 litres and 1.053. EOB was 10 litres into fermenter, 2.5 litres of trub so 12.5 litres and 1.065. 12 points gain.

So now Im really confused. How can I lose 4 litres on my first brew but because I had set the evaporation loss to 3 litres in BS, my gravity gain is the closest its ever been? But then the next brew I set the Evaporation loss to 4 litres and I end up losing 5 litres.
I had 10 litres into the fermenter once cooled. And another 2.5 litres of trub. so 12.5 litres, maybe 13 litres at EOB so still a loss of 4.5 litres.

I dont know whats wrong with my BS settings.
« Last Edit: March 11, 2018, 05:39:34 PM by Truman48 »

 

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