(DONE) Batch size - an overloaded term?

[LarryBrewer]

A brewer has brought it to our attention that batch size is not as simple as it sounds...

There are three possible definitions of 'batch size':

• The final kettle volume after chilling, before draining.
  The amount going into the fermentor. (How Brewer's Friend works)
  The amount of beer you get to drink.

So, how do you personally define Batch Size?

Kettle volume is a helpful, yet complex measure, as kettle dead space and hops absorption losses subtract away sweet wort. We could introduce a way to set a recipe into 'kettle volume' mode. This would only apply to All Grain and BIAB methods, as topping off with water in an extract or partial mash batch makes the final kettle volume less important.

There could still be variations in mash tun dead space, but that factors into mash efficiency. Brewer's Friend uses Brew House Efficiency (http://www.brewersfriend.com/2009/06/27 ... y-defined/).

Two brewers with different efficiencies would have to use different amounts of fermentables to hit the same OG (which means it is a different recipe anyway).

We could introduce a flag for 'how much beer you get', but then the tool needs to add back looses from bottling, racking, and sampling to figure out the volume to use for calculating OG, SRM, IBU, etc. That just gets way too complicated in my opinion.

Input appreciated!

 

[JAMC]

Re: Batch size - an overloaded term?

That's a good question. I'll try and share my experiences and hope it helps!

I've recently changed my methods a little, which resulted in me having to re-calculate the batch sizes for my recipe. I'd previously been working with the following assmptions for a 60 minute boil;

- pre boil volume = 27.25 ltr (6 gallons)
- post boil volume = 23.75 ltr (5.25 gallons)

but to make the most of the cold break and protofloc tablets I've now increased the volumes to....

- pre boil volume = 29 ltr (6.4 gallons)
- post boil volume = 25 ltr (5.5 gallons) <-- I've noticed that this becomes 24.75 litres at ambient temps.

The increase is to take account of the trub being left behind in the kettle after transferring to the fermenter - typically about 3 litres.

I've found the kettle volume to be very helpful in understanding how volume impacts OG. Increasing the batch size in the kettle to compensate for post-boil losses dilutes the recipe, lowering the gravity potential. However, the above post also indicates that there's merit in keeping track of losses further down the line, which I would agree with. I may get 25 litres into the fermenter, but I'll be having a good day if I manage to bottle 22 litres.

The only thing I can suggest is to give people the opportunity to record all aspects, whilst retaining the key role that kettle volume plays.

 

[sbaclimber]

Re: Batch size - an overloaded term?

A brewer has brought it to our attention that batch size is not as simple as it sounds...

There are three possible definitions of 'batch size':

• The final kettle volume after chilling, before draining.
  The amount going into the fermentor. (How Brewer's Friend works)
  The amount of beer you get to drink.

So, how do you personally define Batch Size?

I personally use definition b) "The amount going into the fermentor."
Simply because this is also the point at which I measure my OG.
(I have never understood the reason to measure OG pre-boil...)

 

[LarryBrewer]

Re: Batch size - an overloaded term?

Brewer's Friend uses Brew House Efficiency, which does have one weakness - it is thrown off by hops absorption (more hops = less efficient, on same equipment).

It would be neat to support 'in the kettle' for batch size someday. First it would be a recipe editor option. Then it would appear in the brew session feature. It would also impact what you log on brew day. You would need to record final kettle volume, and final kettle gravity. If final kettle volume is hard to get (like on my kettle which doesn't have a sight valve) you could record the primary fermentor volume and then add back on the estimated kettle dead space and hops absoprtion.

Is this just splitting hairs at this point??

 

[KnowItAll]

Re: Batch size - an overloaded term?

Input appreciated!

You asked for it.

This would only apply to All Grain and BIAB methods, as topping off with water in an extract or partial mash batch makes the final kettle volume less important.

For all but extract brewing, kettle volume (pre or post boil) is an important measure, since it is only with that, combined with OG, that mash efficiency can be determined. Without knowing your mash eff, even for partial mashes, you will not know where your system losses are occurring.

Final kettle volume, even for extract brewers who blindly top off the fermenter, is still a good number to know, since it tells you your boil off rate. This can affect hop utilization if you are severely under or over estimating your boil off, but the effect isn't that significant. More importantly, it provides you with information and habits that will be crucial if you plan to move to all grain brewing.

There could still be variations in mash tun dead space, but that factors into mash efficiency.

The same argument could be made about only measuring fermenter volume and SG for computing efficiency, there is a loss of information about what happened, unless intermediate measurements are made/defined.

Brewer's Friend uses Brew House Efficiency (http://www.brewersfriend.com/2009/06/27 ... y-defined/).

Brew House Efficiency is defined everywhere, except for a few homebrew-centric software packages, as 'in the kettle'- either as yield per pound, or extract achieved related to lab extract. Redefining 'brew house efficiency' as 'to the pub urinal', even with a field for losses resulting from 'bad aim', wouldn't make it valuable statistic. Similarly, basing things off efficiency 'to the fermenter' only results in a loss of information as to where exactly the losses occurred, and how to predict effects if something is changed.

Two brewers with different efficiencies would have to use different amounts of fermentables to hit the same OG (which means it is a different recipe anyway).

I wouldn't call that a different recipe, it is the same recipe adapted to a different system. A recipe is specification for an end product's qualitative values (IBU, SRM, ABV, etc.), and the inputs used to achieve those values for a specified final volume at a particular stage. These inputs are a combination of a grain bill, mash schedule, hop schedule, mash eff, boil off, final volume, etc. If one system needs to increase the grain bill to account for different mash efficiencies to achieve the same starting boil volume and SG as the original system, I don't see how that makes it a different recipe. The same could be said for adjusting hop quantity for hop AA%, kettle losses, increasing batch size, etc.

We could introduce a flag for 'how much beer you get', but then the tool needs to add back looses from bottling, racking, and sampling to figure out the volume to use for calculating OG, SRM, IBU, etc. That just gets way too complicated in my opinion.

It isn't that complicated, once you drop the notion of 'in the fermenter' being some unifying theory of everything. If a brewer wants to brew a recipe, and end up with a certain quantity in his fermenter, the post boil losses on the way to the fermenter just need to be estimated/calculated. Whether that starts from a kettle volume, with further losses subtracted from that, or a fermenter volume with lossed added to it, it is EXACTLY the same thing. However, just as the hop loss/absorption issue has exposed, it is much more difficult to start with an efficiency value 'to the fermenter' that has too many things rolled into it. Using 'to the fermenter' efficiency requires adjusting that value any time losses are either adjusted by the user, or accounted for automatically by the software. Going off kettle/mash efficiency, it is a simple matter of increasing (scaling) the kettle volume to account for the post boil losses. No historical/empirical inputs need to be changed, since nothing pre-fermenter transfer has changed.

This approach is much simpler, since any post boil losses, which have no bearing on any losses (mash eff) prior to the boil, don't require a recalc of the efficiency the user inputs into the software; yet, using a 'to the fermenter' eff, they do. There is no way to untangle that knot, without at some point generating, and using, 'to the kettle eff'.

I don't want to sound like a total corksucker, but I don't think this is an issue can be resolved by mob rule, or some feel good 'consensus building' exercise. This is a cut and dried issue.

I would like to see an opposing view that can justify the position of using both efficiency and batch volume as 'to the fermenter', and I am not saying that the software shouldn't provide mechanism to auto-scale a batch to meet a fermenter volume. I am talking about spec'ing recipes, inputs related to you system, and what measurements to take on brewday to refine/tune your systems performance numbers.

 

[KnowItAll]

Re: Batch size - an overloaded term?

That's a good question. I'll try and share my experiences and hope it helps!

I've recently changed my methods a little, which resulted in me having to re-calculate the batch sizes for my recipe. I'd previously been working with the following assmptions for a 60 minute boil;

- pre boil volume = 27.25 ltr (6 gallons)
- post boil volume = 23.75 ltr (5.25 gallons)

but to make the most of the cold break and protofloc tablets I've now increased the volumes to....

- pre boil volume = 29 ltr (6.4 gallons)
- post boil volume = 25 ltr (5.5 gallons) <-- I've noticed that this becomes 24.75 litres at ambient temps.

The increase is to take account of the trub being left behind in the kettle after transferring to the fermenter - typically about 3 litres.

I've found the kettle volume to be very helpful in understanding how volume impacts OG. Increasing the batch size in the kettle to compensate for post-boil losses dilutes the recipe, lowering the gravity potential. However, the above post also indicates that there's merit in keeping track of losses further down the line, which I would agree with. I may get 25 litres into the fermenter, but I'll be having a good day if I manage to bottle 22 litres.

The only thing I can suggest is to give people the opportunity to record all aspects, whilst retaining the key role that kettle volume plays.

This post illustrates, perfectly, two of the pitfalls of 'to the fermenter' batch and, especially, efficiency.

I envision software that would automatically re-scale the recipe if I increased trub loss or kettle-to-fermenter losses, especially if I have been told to specify my target volume as 'to the fermenter'.

This post also exposes how most brewers don't comprehend that they must change their 'brew house efficiency' even if a post boil loss is adjusted, as well as exposing the amount of manual mojo required to get the numbers correct in response to a change in a post boil loss.

I will abstain from commenting on the educational benefits that could have been gleaned from adjusting post boil losses in the equipment profile.

 

[LarryBrewer]

Re: Batch size - an overloaded term?

This is a pretty interesting read for those who want even more background on the subject:
http://braukaiser.com/wiki/index.php?ti ... efinitions

Given that we have so many existing recipes, and folks are used to doing it the way it currently works (and like it that way), the existing logic will continue to be the default.

What we need next is constructive suggestions for how to handle it. Let me start.

A) I can imagine a 'kettle volume' checkbox on the recipe editor that lives next to the batch size field. When that is checked, efficiency is now 'kettle efficiency', the brew feature will adjust the water calculations accordingly, and the actual efficiency calculation will use different inputs. This could even be a drop down (defaulted to fermentor volume) so it is even more clear what batch size refers to.

B) When the recipe is shared or exported, we will be clear what batch size means (and perhaps we should clarify what it means in all cases).

C) We could make a profile setting so 'kettle volume' is the default behavior if a brewer wants it to be.

D) The Brew feature could show a preview of what the water requirements are to give you a chance to adjust things before you brew (so you know about how much beer you are going to get). I actually want this personally, to dial in my actual boil volume in advance.

 

[KnowItAll]

Re: Batch size - an overloaded term?

Brewer's Friend uses Brew House Efficiency, which does have one weakness - it is thrown off by hops absorption (more hops = less efficient, on same equipment).

This is not the only weakness, or even the main weakness, I see regarding the use of 'to the fermenter' as 'Brew House Efficiency'. Using a baseline 'to the fermenter' efficiency for a standard recipe with a baseline hop bill, then adjusting efficiency for the current hop bill is not that difficult. Unnecessarily complex, confusing, obfuscatory- yes, it is that.

It would be neat to support 'in the kettle' for batch size someday. First it would be a recipe editor option.

When importing, sharing, or manually entering recipes from books, I feel that using 'batch size' and 'brewhouse efficiency' as 'in the kettle' should be the default recipe import/export mode. Especially since doing otherwise would involve building a complete equipment profile for no reason. Is it somehow easier to enter it for a phantom equipment profile, or try to manually scale it to your current system?

For building a recipe truly from scratch, it makes sense to build it to whatever your preferred target vessel and volume is, and for your preferred equipment profile. The 'recipe' should still be stored as an 'in the kettle', equipment agnostic, standardized form for sharing and scaling.

The qualitative values are most important when building/sharing recipes. The quantitative values are mostly used for scaling to account for system and ingredient differences, while still matching the qualitative numbers.

Then it would appear in the brew session feature. It would also impact what you log on brew day. You would need to record final kettle volume, and final kettle gravity. If final kettle volume is hard to get (like on my kettle which doesn't have a sight valve) you could record the primary fermentor volume and then add back on the estimated kettle dead space and hops absoprtion.

How are you supposed to know whether you have boiled off the correct amount if you don't measure, even grossly, kettle volumes? It can be done easily with notches on a brew paddle or guide stick, and is no different than having to mark the fermenter to know what volume made it there. For either method, the the trub pile needs to be poured into a pitcher, or otherwise measured, unless it is at known dead space level.

The arguments for 'in the fermenter' always seem to infer that there is more work involved with 'in the kettle'. If you want to knowing your systems numbers, it involves the same amount of work. That work only increases the further downstream you want to know numbers, or only decreases your knowledge the further downstream you start your measurements. So, if you want to know your system's numbers, 'to the fermenter' actually increases the work that has to be done by one measurement- volume in the fermenter.

Is this just splitting hairs at this point??

I guess it depends on whose hair is getting split, who is holding the knife, and how many home brews he has had.

I feel that knowing 'to the fermenter' as an efficiency measurement is superfluous; using it as a basis for tuning, or compensating for, system performance is fatally flawed; specifying recipes, especially when importing/inputting from other sources, as 'in the kettle' is a much more sensible approach; and having a tool that can scale a recipe, however it is specified, to meet a brewer's target volume be it in the kettle/fermenter/keg/bottle/(urinal), should be a requirement for brewing software.

 

[JAMC]

Re: Batch size - an overloaded term?

This post illustrates, perfectly, two of the pitfalls of 'to the fermenter' batch and, especially, efficiency.

I envision software that would automatically re-scale the recipe if I increased trub loss or kettle-to-fermenter losses, especially if I have been told to specify my target volume as 'to the fermenter'.

This post also exposes how most brewers don't comprehend that they must change their 'brew house efficiency' even if a post boil loss is adjusted, as well as exposing the amount of manual mojo required to get the numbers correct in response to a change in a post boil loss.

I will abstain from commenting on the educational benefits that could have been gleaned from adjusting post boil losses in the equipment profile.

Further experimentation with this new method suggests that 3 litres trub loss was overly-optimistic. It's more like 5 or 6. As a result, a 29 litre pre-boil volume equated to 18.5 litres bottled. Or at least it would have done had I not run out of bottles at 18 litres and drank the last pint straight out of the bucket. Waste not want not...

 

[LarryBrewer]

The October 2012 release allows you to set your all grain recipe batch size mode to 'kettle'. That means efficiency then stands for 'kettle efficiency'. See details in our blog post here:
http://www.brewersfriend.com/2012/10/23 ... -upgrades/