Beersmith Volume Calculations

[coopsomulous]

Hi Everyone

I have a feeling that I'm missing something obvious with my setup but here we go.

The last few brews I have been doing I have missed my post boil SG. Volumes are all good and the pre-boil S.G is good as well. For example, with todays brew I obtained the following. (Note that my mash target volume and SG were spot on)

Pre Boil Volume 29L (@ 75degC) - target 28.59L
Pre Boil S.G. - 1.037 - target 1.037

Post Boil Volume - 21.5 (@ 15degC) - target 21.84L
Post Boil S.G. - 1.046 - target 1.050

I know im only missing .004 SG points but its annoying me. The what I am thinking is that I am taking the pre boil volume at ~ 70 - 75 degC and it actually should be done at the boiling point. The engineer in me is thinking i need to correct the volume for temperature.

When do you take your pre boil volume and do you correct for temperature?

 

[marksy]

I do my pre-boil when the rolling boil starts, and post boil before I cube. You'll need to correct for temps. And don't fill your hydrometer vessel with hot hot wort or it'll warp ( if its plastic). Beer smith has temp corrections. Also make sure your thermometer is accurate. You'll be surprised how far they can be off at certain temps. My two are 5c off each other at higher temps and correct temp is bang in the middle of them.

 

[TheWiggman]

As marksy said, double-check that your SG readings are in fact correct. Considering you're spot on with your pre-boil though I don't think this is the case. If you're using a refractometer, temp shouldn't have any impact on your reading providing you're allowing it to cool before checking your SG.
I find it hard to beleive that you're only losing 9 points on a boil that drops 26% volume with that kind of SG.

If you're consistently getting the same results, I would aim 4 points higher on your pre-boil (i.e. shoot for 1.041 instead of 1.037).

Dumb question but are you boiling for the same amount of time as set in BeerSmith? Based on your volumes I'd say so.

 

[coopsomulous]

Im using a refractometer for SG and allow it to cool so there is no issue wiith temperature. Boil times are being recorded correctly - i usually use the mobile app as a timer for reminders to add things during the boil.

Ive done some quick calulations at work and can account for 2 SG points due to volume changes with temperature - correcting all volumes to the same temperature (in this case 99degC but correcting to 15degC gives the same result)

The other two points i would be happy to attribute to measurement error. - i.e. the forgotten 0.5L in the hose and pump from the whirpool immersion chiller and assume +/- 0.25L from the volume measurement from my dip sticks for volume measurement.

Thanks for the assistance

 

[Dan Pratt]

Hi Tommy,

I have had the issue myself with BS software, its always asking for a 10 point gain in gravity from Preboil to Post boil (90mins) and my system only gets me 7. I have been round and round the figures to nut it out but its purely what my system gets me.

From what I can find online the normal gains are 1gravity point per 9mins of boil, anything more than that is considered great and I am only getting 1 per 13mins of boil....BS calculates to 1 per 9mins, if you change you boil time then preboil gravity will decrease due to more water from the sparge and the expected gains of gravity from pre to post boil is larger. ( I done a 2 hr boil on teh weekend and had 14points of gravity )

Im now designing my recipes to be 3 points higher and that should hit my target OG for that recipe.

 

[Adr_0]

Two quick points:
I think the 'loss to trub and chiller' term isn't calculated correctly, ie the brackets aren't in the correct spot. Could be wrong here so apologies to Brad if I am. If you set this to zero, you then need to instead add this to your batch size to compensate for this. You will end up 'short' in fermenter volume if it's wrong, but should be closer on SG

Secondly, at what temperature do you measure your preboil volume and SG? I'm sure that you compensate in your SG calculation BUT (in capital letters) if your preboil is only 75-80°C then your Beersmith Preboil vol/SG numbers aren't quite correct. Solution is to either measure at 100°C (both volume and SG) or - significantly more simple - call your cooling shrinkage only 3%.

Both of those together should get you spot on.

EDIT: Actually, we're a little unlucky with the shrinkage adjustment. It's valid but the calculation doesn't change the OG... so the way it's calculated you have to measure your pre-boil SG and volume just as it's boiling. This probably helps to get a more accurage pre-boil SG reading anyway due to mixing of the wort (if you draw off at the bottom through the tap in the kettle you may get the more dense wort).

 

[Adr_0]

Sorry TommyC - I was more answering Pratty1 above, as it looks like you figured it out about the difference in preboil SG/vol temps vs what Beersmith assumes.

One thing though, the 'loss to trub/chiller' should be set to zero litres. I don't believe this is calculated correctly in Beersmith (or everyone makes the incorrect assumption) and instead you should add this volume to your total batch volume and recognise that you will actually be 1-2L short but your SG should be correct.

 

[coopsomulous]

Adr_0, thanks for the tips. Ill make some changes for my next brew and see how things go.

 

[marksy]

Adr_0, thanks for the tips. Ill make some changes for my next brew and see how things go.

Have you made your equipment profile? Or just using one in beersmith. You really need to take the time to set beersmith up. My biggest issue was collecting the right amount of wort and then boil off. I now have it down packed, that I can fill 2 cubes and the last one just fills up (sometimes I need to tip the kettle a little to get the last 200ml). It also took me awhile to get a good mash eff out of my eski, but that was partly my thermometers being out from each other. Anyway I pretty much have been hitting mark give or take a couple points. My calculations are based off the two cubes total volume. I then dilute the cubes down to 4-4.5%.

But it did take a few brews to get it to where I'm at now.

 

[Adr_0]

Have you made your equipment profile? Or just using one in beersmith. You really need to take the time to set beersmith up. My biggest issue was collecting the right amount of wort and then boil off. I now have it down packed, that I can fill 2 cubes and the last one just fills up (sometimes I need to tip the kettle a little to get the last 200ml). It also took me awhile to get a good mash eff out of my eski, but that was partly my thermometers being out from each other. Anyway I pretty much have been hitting mark give or take a couple points. My calculations are based off the two cubes total volume. I then dilute the cubes down to 4-4.5%.

But it did take a few brews to get it to where I'm at now.

How specific can you get with kettle setup, eg dimensions and heat input? I haven't seen a lot of setup potential other than mash tun heat capacity, volume and deadspace.

To me the biggest thing with you getting your volumes correct would be grain absorption (in Advanced) and mash tun deadspace. I guess this does have big follow-on effect on SG.

If you know how to do more detailed setup I would love to know.

 

[marksy]

Yeah just all that stuff. Dead space, grain absorption, boil off and trial and error.

 

[dicko]

I was one who measured water volume for brewing with an industry standard 5 litre volume plastic measuring jug. It had 100ml increments and I assumed for years that this was accurate.
It wasn't until I got a BM and made a dip stick for it based on my volume measurements that it was pointed out to me that the measurements were in fact incorrect.
I made a duplicate dipstick for a friend of mine who also has a BM and with him having descrepencies in Beersmith, he decided to weigh the water to check the volumes.
Long story short, my volumes were out 1 litre over 25 litres. From this I made a new dip stick by weighing all the water and from then my Beersmith calcs are always spot on.
Having said this, you do need to establish the correct boil off rate, I use the formula in litres over time, and the exact grain absorption that has been touched on above.
I do what Adr said above and do not bother with kettle and fermenter losses. IMO this is extremely confusing in Beersmith.
My calcs are based on the fact that I need a finished volume of 19 litres into a fermenter, plus the loss from the fermenter, plus the loss from the kettle, plus the shrinkage at cooling (4%) plus the boil off in litres, will give me the batch volume.
I use the batch volume as the final volume and forget the brewhouse efficiency and only use the mash efficiency.
My opinion is that it is the brewhouse efficiency is the confusing bit and really who gives a "rats toss bag" what it is in the home brewing situation anyway.

 

[dicko]

One other thing that comes to mind re Beersmith and figures is that I noticed that when I had a 3v brewery with a gas burner it was extremely important to run the burner to the same intensity each brew. Mine was a Nasa and extremely difficult to get it the same every time.
With the BM and the electric element my boil off is now the same every time.
All these descrepencies can appear to make Beersmith incorrect.

 

[Adr_0]

Hi guys,

Just further on this, looks like Beersmith uses 25°C as the reference temperature for shrinkage. The relevance of this is that you may need to change this under your Equipment (Cooling Shrinkage - default 4%) if you measure your pre-boil volume and pre-boil SG at a temperature other than 100°C. See the below table for a reference:


So you can see that if for e.g. you measure these at mash-out temps (~75°C) this should really be set to 2.3% to make sure your efficiency is calculated correctly once you enter your pre-boil values.

There are probably other larger sources of error - mostly volumes - but it's hopefully one less thing to question the accuracy of.

 

[Adr_0]

Two quick points:
I think the 'loss to trub and chiller' term isn't calculated correctly, ie the brackets aren't in the correct spot. Could be wrong here so apologies to Brad if I am. If you set this to zero, you then need to instead add this to your batch size to compensate for this. You will end up 'short' in fermenter volume if it's wrong, but should be closer on SG

Secondly, at what temperature do you measure your preboil volume and SG? I'm sure that you compensate in your SG calculation BUT (in capital letters) if your preboil is only 75-80°C then your Beersmith Preboil vol/SG numbers aren't quite correct. Solution is to either measure at 100°C (both volume and SG) or - significantly more simple - call your cooling shrinkage only 3%.

Both of those together should get you spot on.

Well, I was a bit wrong here with the "Loss to Trub/Chiller" number being set to zero. I did a bit of playing on the weekend. The shrinkage is right to adjust (see the table above) but you can use the Beersmith efficiency numbers in two ways:

1) Understand that the "Total Efficiency" is brewhouse efficiency, not mash efficiency (white box that can be adjusted). The "Est Mash Efficiency" to the right is calculated based on your expected total/brewhouse efficiency + loss to trub and chiller... so don't put your expected mash efficiency in the "Total Efficiency" box. If you know your loss volume (post boil volume - volume in fermenter) you can adjust your Total Efficiency until your mash efficiency lines up (and your shrinkage) with the pre-boil numbers you measure. Finally put your actual volume/SG in the bottom right for your actual brewhouse efficiency.

2) Set the "Loss to Trub/Chiller" term to 0, so that you can plug in your mash efficiency in the Total Efficiency box (these will be identical now). You will need to add extra on your batch size, e.g. 22L with 1L loss would be 23L. You can still use your actual brewhouse efficiency.

I have been doing method 2 for a while and it has worked for me (can still see mash efficiency + brewhouse efficiency) but this was because I had taken shortcuts rather than aiming to understand everything properly.

Sorry for misleading people. I think I'm not alone in originally failing to hover over boxes and look at interaction of the numbers.

 

[TheWiggman]

Admirable admission of error there Adr0.
I'm going to repeat my same point above - I find it hard to beleive that you're only losing 9 points on a boil that drops 26% volume with that kind of SG. Can someone do the maths on this? I feel like it's something a lot simpler like an erroneous preboil reading.

 

[coopsomulous]

I have finally done the maths and it is most likely due to a bad post boil measurement. It would appear that I havent appeared to account for the wort in my recircuating pump and hoses for the whirpool imersion chiller that was being run during the boil. If i assume that volume is 1L then the expected final SG is only 1.046.

So my solution is as follows:

Add 1L to losses due to chiller into my equipment profile
Adjust boil off to 4 L/h based on this result (was 4.5)

Test changes in brew this weekend

Thanks for everyone's help.

 

[Adr_0]

Now that you know you're loss to chiller /trub accurately you should be spot on if you adjust your shrinkage to your preboil (vol/SG) temperature and remember that the adjustable efficiency (for recipe design) is your brewhouse (into fermenter) not mash. Adjust this brewhouse eff until your mash efficiency lines up with what you measured in your preboil, and your IBU/SG should be spot on based onthe volume into fermenter.

 

[marksy]

If you do a dry run and have a measuring jug you can work this all out. Dead space is loses in your system from kettle to fermenter, boil off, dry run.an you'll get it.