Poll: Does Your Efficiency Drop During The Boil?

[PistolPatch]

Before voting (which I only recently discovered was anonymous in polls - doh!), please ensure that you work on your, "Final Efficiency," figure. This means work on the total volume (including trub) that is in your kettle at the end of the boil. A way too detailed explanation of how to take these measurements can be found here You don't need to be that pedantic though. Also, if your change in efficiency is less than 5%, regard this as no change.

The Reason Behind this Poll

Theoretically, the answer to this poll question for everyone should be number two in the poll. But since starting this topic myself and some others including one professional brewer have found that our efficiency into boiler is about 10% higher than our final efficiency. When I started that poll I had never put much thought into this. I actually thought it happened to everyone.

There have been over 80 posts to that thread, many of them very detailed, trying to work out why this drop is consistently occurring for us. It still has us perplexed. As I wrote there recently, no one has been able to successfully answer the following question as yet...

I have done efficiency measurements using two different sets of instruments and calibrations for both volume and gravity and the figures have matched. I repeatedly get about a 10% drop in efficiency during the boil. So do some others. Why?

This poll will firstly help us work out how many people's figures do vary and secondly hopefully encourage more people to provide their figures in the thread linked below.

If You Are Interested in Discovering the Answer

A lot of great brewers have already put considerable thought into trying to answer the question but we really need more measurements before making any further progress. If you are interested in providing or taking some efficiency figures please read the Edit in Post #1 of What's The Best Way To Post Efficiency On Ahb?

To avoid treading over the extensive ground that has already been covered in that thread please also read the above edit and the posts it directs you to before attempting to answer the question here.

Thanks to all those who have helped in the other thread and also to those who end up helping us here.
Pat

 

[Adamt]

Haven't put a vote in here...

I understand you are working on a final efficiency basis for pre and post boil. However, it makes no logical sense efficiency would drop during the boil. Efficiency is the ratio of malt extraction from the grain to total malt in the grain. Malt/sugar is not lost in the boil, probably not to any measurable proportion anyway, which implies efficiency will not change in the boil. So either this is true or there is something substantial I have missed (10% is a fair chunk).

Working with volume in brewing calculations is a problem, especially when it comes to the boil/mash. Water (and to approximately the same extent, wort) occupies more volume at higher temperatures. However, the mass of sugar/malt in the wort is constant for all brewing temperatures. The first question I would like to pose is: "When are you taking your pre-boil and post-boil volumes?" For this type of calculation you should work at one temperature.

Now, I'm at work at the moment and tremendously bored so I'm going to break out some maths.

Mass (m) is equal to density (p, also SG*1000) times volume (V)

i.e m=p*V

The mass of the sugar in the wort is m(wort)-m(water), note volume of wort = volume of water

m(sugar)=v*(p(wort)-p(water))

All of these properties (volume, wort density (SG*1000) and water density (SG*1000)) must be taken at the same temperature. i.e. If you take your volume measurement at boiling (100C), you must take your SG measurements at 100C too. You can find tables of water density/SG based on temperature here. What I am essentially saying is that at ANY time pre-boil, mid-boil, or post-boil, the mass of sugar in solution (and hence overall efficiency which is this quantity divided by 100% grain yield) is constant, which makes logical sense as only water and other negligible substances (certainly not 10%) are boiled off..

If you take your pre-boil efficiency based on 100C wort volume, and 20C hydrometer readings, then take your post boil efficiency based on 20C wort volume and 20C hydro readings; you will experience a "loss in efficiency" over the boil, where in truth you never had that high efficiency in the first place. (This is because volume is higher at 100C than 20C, and SG is lower at 20C than 100C)

I'm not saying that there is no loss or gain in efficiency during the boil but my logic tells me there's something wrong if boiling is somehow removing (or adding, wouldnt that be speccie!) sugars from solution.

Cheers,
Adam

Edit: Layout

 

[PistolPatch]

Adam you naughty boy!

All this ground and heaps more has been covered in the other thread.

Please read the links in Post #1 to avoid any repetition.

I've got my eye on you mate!


Pat

 

[Adamt]

One thing that isn't covered in there at all is what temperature you are taking SG readings at.

If you take a sample of 100C wort, throw it in a 20C hydrometer tube and hydrometer; the reading will not be at 100C. If you take a sample and drop it on your refractometer is sure as hell won't be 100C (this wasn't answered).

Bayweiss has hit the hammer right on the head; 10% of your sugar in the wort CAN NOT POSSIBLY disappear from boiling. Please explain to me where this sugar is going (this wasn't answered).

These points need addressing before you can start making assumptions about disappearing/conjuring sugar during the boil (which is essentially the argument).

Sorry to be so pessimistic about it

 

[PistolPatch]

Sorry mate but this was covered. It's even covered in the link in the first paragraph of this thread. (I think you're not at work but at the pub - lol!)

I'm going to quote some other things from a post by Thirsty Boy that cover some other areas, besides taking your gravity readings at 20 degrees, that have been covered thoroughly in that thread...

Trub
Hopbag
Deadspace
Chillers
Samples
Thermal expansion/contraction
Spills/boilovers
Leaks
Measurement Accuracy
Wort Expansion

Many difficult hours have been spent on the other thread by many people.

This thread is more of an information gathering thread than an analysis thread.

A good way to keep this thread bumped until we have enough votes though would be if people are experiencing a difference, then to post how much the difference is. It would be interesting if we come up with a common figure.

As mentioned before my loss is around 10%. So is the professional brewers.

Spot ya mate!
Pat

P.S. I knew you'd like this problem Adam

 

[PistolPatch]

Any chance of some more votes here? (Was hoping for more than 12 :huh Even ticking the last box still gives some interesting info.

Also, if anyone is doing a brew today, any chance of recording and posting your pre-boil and post-boil efficiency figures in this thread

MHB has written an informative post here that explains some drop in efficiency pre and post-boil.

Thanks,
Pat

 

[Darren]

Pat,

I am with Adam on this one. There is no way sugar is magically disappearing during the boil. I suspect it is just everyones inability to accurately measure post boil losses to trub, chillers, BOIL-OVERS etc.
The batch-to-batch variation of HB scale brewing makes it absolutely impossible to make the claims that 10% sugar losses are happening. I would say that there are greater than 10% error in any measurement made by homebrewers or microbrewers. Like all biological systems (which mashing essentially is) 10% error is not significant.

cheers

Darren

EDIT: I voted 4. I used to take multiple readings now i just take first runnings and the final gravity. After all they all that matters!

 

[PistolPatch]

Howdy Darren,

I've just started a brew a little while ago. What I'll do (mainly to keep bumping this thread ) is, in one or two posts, describe exactly what my measurement system is and also the figures I score today. It's very simple taking volume measurements with BIAB and a Robinox pot so it will be interesting to see if anyone can explain how I continue to get this 10% loss.

I think you'll see that to explain this loss by measurement error would mean that...

I am either mis-reading my ruler by 2cm on EVERY brew but only at the beginning OR end of the brew or...

I am misreading BOTH my refractometer by 1.3 Brix and also my hydrometer by 6 points but again, only either at the beginning OR ending of EVERY brew.

I don't think I could make these errors even when blind as a bat!

Anyway, you are not the only one to assume it is measurement error.

Let's see what I come up with today in my next few posts.


Pat

 

[Aaron]

Calibration of instruments is also something to consider. An instrument is essentially worthless if not correctly calibrated. Errors are not always linear either so you can't count on having the same degree of error on each measurement.

That said, if you get similar results with multiple measuring devices this may be a mute point. If you really want to make sure about your measurements I would get any measuring instruments you are using professionally calibrated. That could be an expensive step to take for home use though.

 

[Darren]

Howdy Darren,

I've just started a brew a little while ago. What I'll do (mainly to keep bumping this thread ) is, in one or two posts, describe exactly what my measurement system is and also the figures I score today. It's very simple taking volume measurements with BIAB and a Robinox pot so it will be interesting to see if anyone can explain how I continue to get this 10% loss.

I think you'll see that to explain this loss by measurement error would mean that...

I am either mis-reading my ruler by 2cm on EVERY brew but only at the beginning OR end of the brew or...

I am misreading BOTH my refractometer by 1.3 Brix and also my hydrometer by 6 points but again, only either at the beginning OR ending of EVERY brew.

I don't think I could make these errors even when blind as a bat!

Anyway, you are not the only one to assume it is measurement error.

Let's see what I come up with today in my next few posts.


Pat

Pat,
Refractometers and hydrometers are not accurate instruments at the best of times let alone during the confusion on brewday (at my house anyhow). Any residual water/wort in or on either of these instruments will really skew readings. Slight variations in temps (pre-boil v's post-boil) could be culprits too. Also, as Aaron said, your diferences could simply be inherant with HB instruments.


Out of curiosity, how much water are you boiling off during the boil? How are you measuring trub/chiller wastes? They are most likely your problems.

As I said before, I don't think 10% is significant anyhow.

cheers

Darren
What is your

 

[PistolPatch]

Howdy guys,

I boil off close enough to 10 litres in a 60 minute boil. Here's everything that I've done up to my start of boil.

Firstly, volume calibrations are correct. I say this because I have double-checked again today. Firstly a 3 litre jug into 23 litre fermenter. Match! Added another 14 litres making a total of 37 litres into kettle. On my ruler, this measures 23cm.

This also matches with the mathematical formula for volume of a cylinder. A radius of 22.7cm with a height of 23cm gives you 37.2lts.

So, I don't think we can fault any of this.

To translate all the above, every 0.618cm on my ruler equals 1 litre.

At 63 degress the ruler measurement I got was 23.2. Nothing odd there.

Added 4.25kg of grain and ruler measurement rose to 25.7 at 62 degrees. That's about another 4lts so this figure looks good too.

End of mash I had 25cm at 65 degrees which means I dropped a litre during the mash maybe due to evaporation and/or reading of ruler limits.

Removed bag with grain at 70 degrees and had 21.3cm on ruler a drop of 5.5lts. All sounds reasonable so far.

Also took a refractometer and hydrometer reading a tthis stage. Refractometer = 7.8Brix. Hydrometer cooled to 24.5 = 1.031. Adjusted to 20 degrees = 1.033. Pretty close.

Took another volume and gravity reading 5 minutes into boil and after adding 60min hops. Turned off gas before taking ruler measurement. Scored 20.9cm (33.8lts) and Brix=8.3 with hydrometer reading of 1.032 at 23.5 degrees . Adjusted to 20 degrees = 1.034. So hydro and refractometer match.

This gives me an Efficiency Into Boiler of 86.8%.

Whoops! Forgot to take off 4% for wort expansion. Let's make that 32.45lts at 1.034. Proper efficiency into boiler is 83.4%

What I'll do next is take some readings just before and after the end of the boil.

Spot you then!

 

[Darren]

Pat,

Make sure you WASH and DRY your refracto and hydrotube before taking the next measurements.

cheers

Darren

 

[PistolPatch]

Have some end of boil figures. These have been the hardest to read so far (harder to see lower depths on the ruler combined with steam) so I will have to confirm them after the chill.

15.3cm (with hop bag) = 24.76lts. Less 4% for wort expansion = 23.8lts + 200mls hydrometer sample = 24.0lts. Brix = 11.0. Hydrometer = 1.042 at 24.5 degrees. Adjusted to 20 degrees = 1.044.

Working on the hydrometer figure this gives a, 'final efficiency' of 79.8%.

This is only a drop of 3.6%.

As I said, these were the hardest readings to take so it will be interesting to see if the final figures when chilled match.

Spot!
Pat

P.S. Darren , just caught your post. What I've been doing here is actually rinsing the hydromter tube and allowing it to drain for ten minutes. While this will lower the reading a fraction, the tube takes 200mls of wort so I reckon the diff will be negligible. Anyway, so far the figures aren't looking like they will get my usual 10% drop!???

 

[PistolPatch]

Final Figures Into Fermenter are...

Volume = 20.7 in fermenter plus 3.2lts trub plus 0.2lts sample = 24.1lts
Starting Gravity = 1.043 (Brix reading was 1 gravity points higher so hydrometer reading.)

Final Efficeincy = 78.3%

Drop During Boil = 5.1% (3.2% of this can be explained by MHB's post I mentioned above.)

(Trub was measured by puring hop waste and all remains in kettle into a measuring jug.)

Well this is the lowest difference I have ever had when measuring. I'm confident in the figures above though. One weird thing is that I usally end up with 23 litres in the fermenter exactly. Not today though!

My conclusion - Whilst I am pretty happy with the way the figures balanced I am never ever doing this exercise again :wacko:

It does certainly show though that if someone changes one thing in their brewing process and thinks they have increased their efficiency after one brew by a few percent, they better check several brews before relying on that change.

Thanks for your comments above Darren and Aaron. Must be time for a hundred beers!

LOL
Pat

(Will post a pic later of hydrometer tube with trub at bottom. Might be interesting for some people to see how much there is.)

 

[Ross]

My conclusion - Whilst I am pretty happy with the way the figures balanced I am never ever doing this exercise again :wacko:

cheers Ross

 

[mika]

Had the 'loss of efficiency' on my last brew. 1pt (hydro) under going into the kettle but at the end of the boil I was 5pts under on the final figure.
Will be watching it closely next brew to see what's going on.

Don't wory Pat, we'll catch those evil sugar fairy's in the act ! h34r:

 

[Darren]

PP,

No boil-over today?

cheers

Darren

 

[PistolPatch]

LOL!

Never get boil-overs thank God. She's a friggin huge pot!

Sugar-fairys. Too right! I think there are also beer line fairies, quick-disconnect fairies and spanner fairies and bugger me if a gas fairy hasn't just popped by!

I must ask Rossco how much beer line I have bought....


Pat

 

[Gulf Brewery]

Whoops! Forgot to take off 4% for wort expansion. Let's make that 32.45lts at 1.034. Proper efficiency into boiler is 83.4%

PP

The wort expansion figure of 4% is the difference for water between 0 and 100C, so unless you have a consistent baseline temperature, your figures may be out by a bit.

Also, the refractometer readings vary greatly with temperature. Always cool to around 20 to 25C, wash your refractometer, dry and measure. Try again with a reading near 100% and you will get a variation.

You mention a temperature compensation somewhere for 20C? Is your hydrometer calibrated at 20 or 15 (15.96 or something lke that)
Cheers

Pedro

 

[PistolPatch]

Is your hydrometer calibrated at 20 or 15 (15.96 or something lke that)
Cheers

Pedro

Hold on Pedro. I'll just go and get it out of the bin and have a look

Whoops! Need my glasses as well...

Mine says 20 degrees and my calcs were based on 15.6. Thanks Pedro! I hadn't thought that would make any difference. When I adjust for that, I get....

Start of Boil Efficiency = 78.5%
End of Boil Efficiency = 76.5%

Cool!

Well spotted mate :beer: