Into Kettle vs. End of Boil Efficiency

Post #1 made 9 years ago
I was taking a look at this thread and it got me thinking...I have yet to get my "Into Kettle Efficiency" and my "End of Boil Efficiency" to match up. Why?

In theory, these two values should always be the same since it's simply the total extract points (gravity x volume) divided by the maximum extract potential.

So, G(start) x V(start) / EP = G(end) x V(end) / EP where G is gravity, V is volume and EP is max. extract potential. Doing simple algebra,
G(start) x V(start) = G(end) x V(end)
which is equal to the number of extract "points".

These two values are inter-related by and influenced by evaporation: as water evaporates the volume decreases but gravity increases. So why have my values been different? Does anyone else experience this? I don't care that they don't match up (ok maybe a little only because I'm a chemistry grad student and I'm supposed to care about things like this) I'm just mostly curious.

First off, I assume that it is just simply due to errors in measuring either the volume or gravity. This would be the logical reason and I'm perfectly happy to except that. But for the sake of creating something out of nothing :) , why then is the "End of Boil Efficiency" always lower (for me) than the "Into Kettle Efficiency"? If this was simply a random measurement error, then this should not be a trend. (Keep in mind that I only have a handful of brews under my belt so not a lot of "data points".)

So, discuss away...

Does anyone experience this?
Does it follow the same trend ("End of Boil Efficiency" lower than "Into Kettle Efficiency")
Am I a complete idiot and over-looking something?
Last edited by BrickBrewHaus on 09 Mar 2011, 00:20, edited 5 times in total.

Post #2 made 9 years ago
Hi BB, my thoughts are that it just a matter of measurement. Unless we use accurate measuring equipment, it's difficult to determine true efficiency. So I think the discrepancies are more likely from small errors in reading volumes and/or gravity.

For me, I take an end of boil volume measurement (accurate to 1/2 a litre) and an OG reading after transferring from no-chill cube to fermenter. I use these 2 figures to give me an end of boil efficiency.

It's my opinion that we can all get hooked up on numbers, when we are all trying to make beer. It's good to know that you have an efficient system, but it's better to know you can make great beer!
"It's beer Jim, but not as we know it."

Post #3 made 9 years ago
I too try not to get hung up to much on the numbers as personnally I find it counter productive. However, as into kettle eff' should = end of boil eff' why not add the 2 together then divide by 2, therefore averaging out any measurement errors. :thumbs:
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Post #4 made 9 years ago
hashie wrote:It's my opinion that we can all get hooked up on numbers, when we are all trying to make beer. It's good to know that you have an efficient system, but it's better to know you can make great beer!
I agree completely. Making great beer is absolutely the top priority, but I also enjoy thinking about the numbers. I'm a very analytical person and always want to know the "hows" and "whys" behind things. So when I'm consistently getting a couple of numbers that, in theory, should be identical end up different, I start to wonder why :scratch: . This is usually what occupies my brain between brew sessions, but during a brew day I really only pay attention to my OG and how that compares to the anticipated OG, maybe a few other things but I don't fret about much.
Last edited by BrickBrewHaus on 09 Mar 2011, 05:43, edited 5 times in total.

Post #5 made 9 years ago
This pre and post-boil discrepancy thing is very common. I get it quite consistently and, like you, have always scratched my head on this one. I did a poll on this a few years back on another forum but only one answer made any sense to me. I'll do some searching later today and see if I can find that answer. While it didn't account for a big difference, it did account for some. :peace:
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Post #6 made 9 years ago
Do you take your start of boil reading when your wort stars boiling or before that?

If you don't wait until the wort is boiling then it's not the same temperature as the end of boil reading, which leads to a difference due to expansion. Also do you wait for both samples to cool to say 40C before doing the SG?

Mne pretty mch match up
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Cubed: -
Stirplate: -
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Post #7 made 9 years ago
stux wrote:Do you take your start of boil reading when your wort stars boiling or before that?
I take the pre-boil gravity immediately after pulling the back, so probably ~170 F. Then I take the OG reading after the wort is chilled.

I think you're getting to another possibility, one that I hoped someone would bring up. I'm pretty sure the volumetric expansion of water (not wort) is ~4% from 20C to 100C. At mash temps (which is when I take the pre-boil gravity) is probably half this if I had to guess. The discrepancies I've seen aren't accommodated by this small expansion, i.e., increased volume therefore increased extract points for the pre-boil measurement.
Last edited by BrickBrewHaus on 09 Mar 2011, 10:14, edited 5 times in total.

Post #8 made 9 years ago
I'm no chemist or mathematician (did I spell that right?) but I was thinking along the lines of:
a high efficiency into kettle means that you have lost very little to absorption by the grain, whereas a lower end of boil efficiency may mean that you haven't used enough grain, which is why the efficiency into kettle is so high. Hope this makes sense.

edit: What was I thinking when I wrote this?
Last edited by BobtheBrewer on 10 Mar 2011, 09:45, edited 1 time in total.

Post #9 made 9 years ago
Okay, I found the old thread I started and (after reading 102 posts, a lot of them very long thanks to you know who :roll:) found the quality answers :). In that thread, all the obvious reasons were covered and dismissed. At that time, I also did several brews and measured very carefully with a double-checking system. No holes there.*

The best answer I received was from 'MHB' who has a bag full of brewing qualifications and experience. Here are his two posts...
Just a thought about the "Missing Mass".
I haven’t sat down and run the numbers through however:-

The hot break material is in solution at the start of the boil, it's on the bottom of the kettle at the end of the boil.

This mass does contribute to the sweet water density.
But it is missing from the wort density.

It might account for some of the change in calculated efficiency.

MHB
Ref Kunze; Technology Brewing and Malting
Hot Break is typically about 1.42 Kg/100 L
Cold Break about 0.22 Kg/100 L

Just a quick play with the numbers (I realise that there are some other factors, but I think they are below the resolution of the measuring equipment in use)
Total break material ~1.64 Kg/100L,
If the sweet wort was say 1.050
You loose from the solution about 1.42g/L on Boiling and another 0.22g/L on Cooling a total of 1.64g/L.
So you loose some apparent density, the true value for the sugar content of the sweet wort should be ~1.04836, rather than 1.050.
0.05-0.04836 = 0.00164
(0.00164 / 0.050) X 100 = 3.28%

About a 3.3% apparent loss in efficiency; caused by break formation.

Break once it forms can't be stirred in and measured; it has come out of solution, it has no more effect on the gravity reading than would a teaspoon of sand in the bottom of your hydrometer tube.
Even if it's stirred into suspension, it won't affect the gravity reading.

MHB
Bloody hell! :thumbs: :thumbs: :thumbs:

For various reasons, at the time I started that thread 4 years ago, I didn't realise the full impact of the above quotes. In fact, it has only hit me just this minute. Go figure :P.

When studying this sort of thing, it is very hard though to draw any conclusions until we collect more figures. BBH started this thread because I had listed some average efficiency figures. These came from this spreadsheet...
BIABrewer Register.xls
If you study the spreadsheet, you'll see that any single brew varies - often wildly.

*(Just on my brews alone, as many brews show an increase in efficiency as a decrease during this time.)

I find this sort of topic really interesting but it's also dangerous :P. I suspect there is a slight drop in efficiency readings pre and post-boil for the reasons MHB has mentioned but until many brewers gather together and pool their records, all this is just anecdotal. And, as BBH well knows, in the scale of things, it isn't really that important.

Interesting though :drink:
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Last edited by PistolPatch on 09 Mar 2011, 20:11, edited 5 times in total.
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Post #10 made 9 years ago
I guess the above posts give good reason to try and take readings in similar circumstances, ie take both pre and post boil volumes @ boiling, and chill both gravity samples to ~ 20 deg C, this it what I did on my last brew and my pre and post boil Eff. were 0.9% different.

Also may have been a coincedence :scratch: or fluke :lol:
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Post #11 made 9 years ago
PP--Thanks for that. That's something that I've never considered and something that makes perfect sense. :clap:

So in my case I'm probably seeing discrepancies from 1) taking pre- and post-boil volumes at different temperatures, and 2) loss of wort density due to separation of hot & cold break.

I think I'm satisfied with that :smoke:

Post #12 made 9 years ago
I think, from all of this, it would be great if we could have a forum standard for efficiency.

I would propose end of boil, as that is what most people would use, I think?

What say you all?
"It's beer Jim, but not as we know it."

Post #13 made 9 years ago
hashie wrote:I think, from all of this, it would be great if we could have a forum standard for efficiency.

I would propose end of boil, as that is what most people would use, I think?

What say you all?
I think a lot of guys around here would say that having an efficiency standard is the right way to go, myself included. So +1 for me.
Last edited by BrickBrewHaus on 10 Mar 2011, 22:30, edited 5 times in total.

Post #14 made 9 years ago
hashie wrote:I think, from all of this, it would be great if we could have a forum standard for efficiency...
[I am pretty sure that hashie wrote the above just to stir me up - he knows what a massive problem this is and how I love writing essays on it :lol:. The bastard better read every single word I write below :P]

Funnily enough, that old thread I copied MHB's quotes from above tried to tackle just this issue of defining efficiency when used without the qualifications, "into kettle," post-boil,' into fermenter,' "into packaging," etc.

No joy there unfortunately and I can't see there being any joy soon for a few reasons...

1. Home brewers generally do not use the term correctly. The term, "efficiency," cannot have a figure applied to it because the term refers to all efficiencies. So, of the following two sentences only one is correct...

a) "Sometimes, not adjusting your mash to the right pH can have a considerable effect on efficiency."

b) "I forgot to adjust my mash for pH and my efficiency dropped by 5%."

The first sentence is correct. Sometimes, not adjusting your mash to the correct pH will lower your efficiency into the kettle (pre-boil) and your efficiency post-boil and your efficiency into the fermenter and your efficiency into packaging.

The second sentence means nothing. If it said, "efficiency into the kettle," or maybe "efficiency into the fermenter," then it would be correct.

So, the word, "efficiency," should be used as a generic term that includes all efficiencies.

2. "Brewhouse Efficiency" - The above problem occurs because many brewers assume that "effficiency," is short for, "brewhouse efficiency." Even if it was, next time you are having a beer with fellow brewers, ask them what they think brewhouse efficiency really means. I have run polls on this and the answers are frightening. I have corresponded with highly trained brewers on this subject and most of them think it should mean what you get into your kegs or bottles but none of them have been entirely sure. (Is your brewhouse your MLT and kettle or is it your MLT, kettle and fermenter?)

3. The problem is constantly compounded - We all start brewing and think we know what efficiency means. Then we do a few brews from different sources and either start scratching our heads or we don't care about figures or when posting recipes we fudge the figures to make them look right. A lot of brewers will just assume that someone has made an error when posting a recipe (or they have made a measurement error) without even considering the possibility that maybe that brewer has a different interpretation of, "brewhouse efficiency," than they do.

What We Could Do

Immediately solving the above problems is impossible even on a young forum like this. (You'd need to get all members to sign an affadavit upon registering that they promise and cross their heart, never to use the word efficiency or brewhouse efficiency without it meaning... :lol: And that they had read everything else in BIABrewer.info Essentials :o)

So, even defining "Brewhouse Efficiency," is not something that is going to happen soon.

Writing the phrases, "Efficiency into kettle,"/"Pre-Boil Efficiency," "Post-Boil Efficiency," Efficiency into Cube," Efficiency into the Ferementer," or "Efficiency into Packaging," takes about the same time to write as the term, "Brewhouse Efficiency."

So, what us more experienced brewers who recognise this big problem can do, on this forum, is always use such phrases. They leave no room for confusion.

Many brewers, especially new ones, are not even aware of the above problem so when someone does write a post saying, "My efficiency was x%," we should take the time to let them know that their sentence is incorrect. Better still, maybe there should be a locked thread here that we can all refer such people to?

Useful figures to emphasise when publishing recipes

When you publish a recipe, the two most useful figures you can hand on to other brewers are (apart from your grain and hop bill)...

a) Your volume at the end of the boil.
b) Your original gravity (which stays the same from the end of the boil right through to pitching.)

There is no need to even state an efficiency figure as the above will readily tell other brewers your post-boil efficiency. But, if you did state it, you should clearly write, "Post-Boil Efficiency." (You will need to write this if you publish your grain bill as percentages.)

Providing the above removes all ambiguity. It saves other brewers having to make many guesses. For a start, they won't have to guess what you mean by "efficiency" or "brewhouse efficiency." They also won't have to guess how much kettle trub they have compared to you or fermenter trub (and for no-chillers, cube trub.)

If all experienced brewers did the above, then we would be accelerating new brew's wisdom in this area and then, one day, recipe conversion will take two seconds :champ:.

:peace:
PP

[Was that long enough hashie? You better have read it slowly and several times too! Anyone who does should be able to become a terminolgy despot just like me :lol:.]
Last edited by PistolPatch on 11 Mar 2011, 19:17, edited 5 times in total.
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Post #16 made 9 years ago
Glad you enjoyed the read joshua. (I think hashie is just pretending he read it :lol:). Thanks for your explanation above as well.

Today, 'The Calculator', has been modified to correct some misleading terminology that it was using. More details can be found in this post. So, that is one step forward.

This post here will also be of interest to those reading this thread.

:peace:
PP
Last edited by PistolPatch on 12 Mar 2011, 22:05, edited 5 times in total.
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