Biab Efficiency Vs Grain Bill Graphs

[RdeVjun]

Dunno if its much help, here's a heap of sparged BIAB data for a 19L pot, the 6kg grainbill isn't mine BTW, nor is it 19L, but you get the trend by normalising it to L of 1.060 per kg. I have a heap of data to update the chart, just haven't had the chance.

 

[MHB]

This is intrinsic to the whole mashing process and why sparging was developed in the first place.
When you mash a certain amount of water stays in the grain, the exact amount will vary with the consistency of the grist, the temperature of the liquor, the protein content and a bunch of other factors, but will generally be between 0.8-0.9 L/Kg.
That water has (effectively) the same extract content as the wort, so clearly if you take out the same L/Kg of water from a high gravity mash as you do in a lower gravity mash, you are taking out more of the extract and lowering the efficiency.
The relationship is a nice linear one like the graph shows, the only out is to sparge in some way to try and get some of the extract back, or just to live with the loss.
Good work on the research Sean O, its nice to see brewers thinking about whats going on. If you want to tighten up the results a bit, calculating the Mash Efficiency will give you a better picture of what the losses due to changing Liquor to Grist ratios are, without having the results skewed by the other system losses.
Good one
Mark

 

[Thirsty Boy]

Sean is reporting exactly the sort of effect that you see with any no-sparge or even batch sparge technique. As the grain bill goes up and the gravity of the wort goes up, the efficiency must come down. You can ameliorate it somewhat by sparging, and make it almost go aways with multiple batches - but unless you are doing a proper fly sparge, your efficiency will always drop as grain bill goes up - if yours doesn't, then i deeply suspect you aren't measuring things as well as you should be.

A point of efficiency per point of gravity is on the high side, but not completely out of order in my experience - especially if you are measuring your efficiency "into the fermenter" because with more grain, there will also be more trub which will also take its toll.

My BIAB efficiencies (measured in the kettle) range from a little over 80 for worts around 1.040 or under to a little under 70 for worts over 1.060, so I'm in the same ball park as Sean.

This is a pretty well documented feature of simple BIAB brewing, but usually people give arm waving descriptions of how much it effects them - Sean has been smart enough to make a simple graph and it seems like a damn good idea to me. I'll bet dollars to donunts that he starts hitting his gravity targets dead center in the near future. nice work Sean.

Strutter - come to the next BIAB demo at G&G (probably in a month or so) and see if you can spot any differences between what Spills and I are doing and what you are doing. Always easier to see where yiu are going awry when you see someone else doing it in the flesh.

 

[Strutter]

YUP, I'll be there, was planning on going to the one just, however time destroyed me


Thanks all

 

[sean_0]

A point of efficiency per point of gravity is on the high side, but not completely out of order in my experience - especially if you are measuring your efficiency "into the fermenter" because with more grain, there will also be more trub which will also take its toll.

Yes, that probably does account for the excessive drop off in efficiency end of the graph. I know I lost about 3L to trub for the biggest beer recorded there, whereas usually it's around 2L.

I think that means that mash efficiency for that big beer was around 71%. - not too bad really

 

[datamike]

I've been noticing a strong correlation between the efficiency I get using BIAB and the strength of the beer I'm trying to make. Also I've read posters here talking about how efficiency falls off at higher OGs.

I've just put together some numbers from my last 5 brews and thought people might be interested to see what it looks like. I've got two graphs, one is efficiency vs. the OG of the beer, the other is efficiency vs. the total grain bill for the beer in kgs.

I'll be using this to help me hit targets in the future.

Nice graphs. Even though the efficiency looks a tad on the low side, the correlation seems spot on. You could probably tweak it higher with a finer crush, proper mash PH, etc.

I've been researching this topic quite a bit recently, trying to get some hard answers about efficiency rates, and gravity limits of BIAB brewing.

If you've been brewing for a while, you certainly heard or read about "efficiency goes down" as the gravity goes up, or "my system loses efficiency on high gravity beers". But why is this??

From my research, it simply correlates to the ratio of sparge water to overall volume. As the grain bill increases, the mash water volume also increases, and thus the amount of water available for sparging is less.

For BIAB, it comes down to "what's the highest gravity we can get without sparging?" Assume there's no limitations imposed by the size of the kettle or the boil volume needed. (both are "hard" limitations that will affect gravity) In my, admittedly rudimentary experiments, it seems to be right around 1.080 or slightly above.

I've taken a small amount of heated water (2 quarts - pretend they're liters ;-) ) and added varying amounts of grain, let sit for an hour, drain and measure OG. The highest reading was 1.082 no matter how much grain is added. Anyone else been able to get a higher reading?

Thoughts and comments appreciated!

Michael

 

[lastdrinks]

I find my efficiency goes up when i do a long stir in at the start of the mash.

 

[Thirsty Boy]

Nice graphs. Even though the efficiency looks a tad on the low side, the correlation seems spot on. You could probably tweak it higher with a finer crush, proper mash PH, etc.

I've been researching this topic quite a bit recently, trying to get some hard answers about efficiency rates, and gravity limits of BIAB brewing.

If you've been brewing for a while, you certainly heard or read about "efficiency goes down" as the gravity goes up, or "my system loses efficiency on high gravity beers". But why is this??

From my research, it simply correlates to the ratio of sparge water to overall volume. As the grain bill increases, the mash water volume also increases, and thus the amount of water available for sparging is less.

For BIAB, it comes down to "what's the highest gravity we can get without sparging?" Assume there's no limitations imposed by the size of the kettle or the boil volume needed. (both are "hard" limitations that will affect gravity) In my, admittedly rudimentary experiments, it seems to be right around 1.080 or slightly above.

Edit. PS - I think kai refers to them as "first worts" so it mightbe easier to find looking for that.

I've taken a small amount of heated water (2 quarts - pretend they're liters ;-) ) and added varying amounts of grain, let sit for an hour, drain and measure OG. The highest reading was 1.082 no matter how much grain is added. Anyone else been able to get a higher reading?

Thoughts and comments appreciated!

Michael

Sparging doesn't increase your gravity, it reduces it by diluting the wort with pure water - it increases the efficiency with which you can move the sugar you create from one stage of the process to another, but it doesn't increase the amount of sugar you create.

What you are testing is the maximum "1st runnings gravity" you can obtain and whatever that maximum turns out to be - it will be independent of whether the mash is sparged, or done in a BIAB bag or traditional mash tun. FWIW i suspect that it will turn out to be higher than 1.082 given everything being perfect, but haven't done the experiments so I'm certainly not saying you're wrong. i think Kai on braukaiser did some experiments with expected first runnings gravities for different L:G ratios, so it might be worth having a nose about his site to see what he found.

 

[datamike]

Sparging doesn't increase your gravity, it reduces it by diluting the wort with pure water - it increases the efficiency with which you can move the sugar you create from one stage of the process to another, but it doesn't increase the amount of sugar you create.

What you are testing is the maximum "1st runnings gravity" you can obtain and whatever that maximum turns out to be - it will be independent of whether the mash is sparged, or done in a BIAB bag or traditional mash tun. FWIW i suspect that it will turn out to be higher than 1.082 given everything being perfect, but haven't done the experiments so I'm certainly not saying you're wrong. i think Kai on braukaiser did some experiments with expected first runnings gravities for different L:G ratios, so it might be worth having a nose about his site to see what he found.

You're right, I am testing 1st runnings gravity, which really is another term for BIAB gravity, no? And doesn't the term "1st runnings" imply that it's the gravity before any sparging (if any) takes place?

I've read Kai's stuff - very interesting, but as he states "theoretical limits". I couldn't find anything with actual data derived from testing. Seems to be all spreadsheet modeling - interesting, but often wrong when it comes to real world brewing, at least in my experience. If I've missed Kai's actual testing of 1st wort gravity, someone shoot me a link if you have one.

We're in the middle of moving, but I plan on doing more testing in the next few weeks.

Michael

 

[Thirsty Boy]

Yes, first worts (or first runnings) gravity is the same thing as BIAB gravity - i'm not arguing that. Its just that i think you are looking at it the wrong way.

If there is (and like you i am sure there is) an upper limit to first wort gravity, then that limit exists in all forms of brewing and has nothing to do with sparging or not sparging - it is the maximum gravity you can get at any stage in your brewery before you concentrate the wort by boiling.

So, if you sparge - you get your maximum, then add water and dilute it, which enables you to remove some more sugars. But to end up with a higher gravity that the "natural" maximum, you have to boil down the now diluted solution.

If you BIAB - you can get your higher gravity by adding both extra water, to reduce the concentration, and adding extra grain to increase the gravity to maximum again. Then you boil the resultant larger volume down to your higher gravity.

Same thing mostly.

The difference is in the efficiency, not the theoretical maximums. Practically of course, at such high gravities, the efficiency limitations of BIAB/no- sparge would become huge and to get the required gravity and volume you would need a stupidly large pot or to make a quite small batch.

Edit- Fwiw, i have seen reports of mashfilters giving first worts with a gravity of 25- 35plato which is 1.100 - 1.150 ish, so that would mean that the absolute maximum lies somewhere north of 1.150. What is realistic or practical at a homebrew level will of course be vastly different.

 

[datamike]

We're definitely on the same page.

I still haven't seen any actual evidence of first runnings gravity about 1.082 or so. What's this "mashfilters" you refer to?

Edit - Ahh ok, bit of searching turned up some info on Cooper's mash filter and reference to first runnings of 26 plato. Interesting! Still, I am interested in the highest pre-boil gravity anyone has achieved with a BIAB setup. If you've gotten above 1.082, please post with the specifics. Thanks!

Michael

Yes, first worts (or first runnings) gravity is the same thing as BIAB gravity - i'm not arguing that. Its just that i think you are looking at it the wrong way.

If there is (and like you i am sure there is) an upper limit to first wort gravity, then that limit exists in all forms of brewing and has nothing to do with sparging or not sparging - it is the maximum gravity you can get at any stage in your brewery before you concentrate the wort by boiling.

So, if you sparge - you get your maximum, then add water and dilute it, which enables you to remove some more sugars. But to end up with a higher gravity that the "natural" maximum, you have to boil down the now diluted solution.

If you BIAB - you can get your higher gravity by adding both extra water, to reduce the concentration, and adding extra grain to increase the gravity to maximum again. Then you boil the resultant larger volume down to your higher gravity.

Same thing mostly.

The difference is in the efficiency, not the theoretical maximums. Practically of course, at such high gravities, the efficiency limitations of BIAB/no- sparge would become huge and to get the required gravity and volume you would need a stupidly large pot or to make a quite small batch.

Edit- Fwiw, i have seen reports of mashfilters giving first worts with a gravity of 25- 35plato which is 1.100 - 1.150 ish, so that would mean that the absolute maximum lies somewhere north of 1.150. What is realistic or practical at a homebrew level will of course be vastly different.