BIABrewer.info

[Like all, "The Basics," in the General Brewing Skills section, the following is not a definitive guide. It is simply a guide that will get a new brewer under way safely and with confidence. Please advise BIABrewer of any errors. Please justify, in full, any contrary topics that you may choose to start in this forum. If well-written and justified, they will be, "promoted," as best as we are able.]





Note that this article needs to make the following points...

1. An efficiency figure is based on taking a gravity reading and a volume reading of sweet liquor, wort or flat fermented beer. Gravity and volume measurements are affected by temperature and usually need to be physically or mathematically manged to get an accurate reading.

2. Efficiency figures based on a single gravity and volume reading are often very inaccurate and cannot be relied on.

3. The new brewer, as mentioned in the Master Guide, should initially concentrate on the taking and recording of readings for their first 5 to 10 brews.

4. Any statement like, "I changed this on my last brew and my efficiency improved by 5%," should be taken lightly." Any statement like, "My first 5 brews averaged x efficiency and my next 5 brews averaged y efficiency," is worth looking into.

5. Efficiency measurements are often wildly inaccurate for a lot of reasons. One major reason is simply through their interpretation. "Efficiency into fermenter," will be vastly lower than, "into boiler efficiency," for example. To keep things congruent, BIABrewers should be encouraged to report their, "post-boil," efficiency. Theoretically, this should be the same as, "into boiler efficiency," but often is not.

6. The term, "brewhouse efficiency," as reported from brewing software is not a good figure to quote to other brewers. It is often derived from incorrect use of software and, in some cases, even the software uses the term badly. It is very hard to find a definitive definition of, "brewhouse," efficiency so when it is used the new or experienced brewer really needs to find out what the source is referring to.

7. BIABrewers, when quoting their efficiency should describe their efficiency figure accurately. For example, "My pre-boil efficiency was..." or "My efficiency into the fermenter was.." New brewers who think they have an efficiency problem should go further still. They should say at what stage they took their reading as well as the gravity of the reading (at room temperature) and the volume of the sweet liquor or wort from which it was taken.

8. Post-boil efficiency is the best figure to work from as gravity of unfermented wort does not change until after pitching.

9. How to take gravity and volume measurements at various stages of the brew needs to be written somewhere but not sure which section to put it in. The importance of temperature on gravity readings and volume should be referred to. For example, if a hot reading is taken, it needs to be covered in plastic wrap and chilled. Hot volume measurements need to be calculated out.

10. Whilst the above discredits the importance of efficiency it is important that major efficiency failures can be identified early by the new brewer. So, this post also needs to give the new brewer a ball-park guide of how to interpretate their readings.

11.There could perhaps be an efficiency failure checklist in future. For now, more experienced brewers should be able to help. Usual failures are, inaccurate or non-calibrated hydrometers, inaccurate thermometers, bag doesn't line the pot, bag of wrong material or no stirring of mash. Never seen crush of grain as a problem. All others have been the causes to date. Whoops, there is another common one - incorrect weighing of grain bill by supplier or the brewer.

12. BIABrewer fears that this subject will take a long time to get right so, for now, when you quote an efficiency figure, please follow the guidelines above as best as you can.

Just thought I'd copy a post I wrote a while ago on another forum regarding BIAB efficiency as there seems to be a lot of incorrect information around. Hope it helps and here you go...



BIAB is actually a very efficient brewing method - about 4.5% higher mash efficiency* than batch-sparging done with a double run-off. This is not based on guesses but on personal experience and science...

1. Personal Experience - Using the same kettle (and this is important) I achieved brews about 4%-5% higher than batch-sparging with a double run-off. Same recipes etc and based on several brews.

2. Science - If you want to wade through this article, you will find that Briggs, a well-known brewing authority, concludes, "that thinner mashes perform better and allow for better extraction of the grain."

It is important to listen to sources that have done the experiments and/or collected the figures. When comparing one batch to another it is also important to ensure the same size kettle is being used. (Larger kettles require more water due to higher evaporation and therefore will yield slightly higher efficiencies due to more water being used.) The figures I have collected from myself and other brewers show an average mash efficiency of 79.25% which is great.

This no miracle. There are several simple reasons why a BIAB brew (raised to mash out temperatures) will give higher efficiency than a double run-off batch-sparge.

A. No "Tun" Deadspace: In BIAB there is no deadspace.

B. Higher Sparge Temperature: In a double run-off batch sparge, it is impossible to get the grain bed to mash out temperatures on the first run-off even when adding boiling water straight to the bed (which isn't a truly great idea anyway.) If adding water at say 78 degrees you will, of course, never be able to get the grain bed to mash out temperature. In BIAB, the entire sparge can be done at mash out temperature. In other words, with BIAB we are able to do a much higher temperature sparge. This is a great advantage.

C. Larger Surface Area Run-Off: With traditional brewing, the run-off from the sparge is confined to the mash tun outlet. Besides possible channelling problems, the sparge is also slow. With BIAB, there is no channelling and the run-off is fast as the wort can escape through the entire surface area of the wetted grain bag. You can drain a mash tun or a bag for several hours and get run-off if you want to. This of course is silly. If however you decide on cutting your sparge at the start of the boil, then you will have drained more liquor from the bag than you will have from the tun. This is the reason why a BIAB grain bed weighs less than a traditional bed.

I hope the above helps,
PP

*Mash efficiency is either efficiency into boiler or post-boil efficiency. Theoretically these two figures should be identical. The brewer's figures I have collected show an average discrepancy of 2.5% between these figures - nothing to get hung up on though. The figure of 79.25% used above is the average of the two.

Wow Pat, that's a pretty comprehensive effort! There's also some now- obvious logic in that too, eg. I'd love to see the highly efficient long run off finish well after the boil has!

From the MaxiBIAB perspective, it actually fits closer to conventional/ old- fashioned L:G (4 for mash, but 1+1=2 for sparge) ratios, however it also yields some pretty decent efficiencies, so we can't really complain about that.

One thing I do wish HBers would be clear about is efficiency, so often we use the two useful metrics of boiler and fermenter efficiency interchangeably, when they're not so (guilty as charged, your honour...). Glad you've cleared it up from the start.

I could go on, but can't top the quality of your posts, these are very succinct and useful summaries, so well done and thanks very much!

Mind you, I suppose anything under two pages is succinct for me .

Thanks for your comments mate - very nice of you.

I hear what you are saying about efficiency definitions. This has driven me up the wall for years! A lot of new brewers think they are getting bad efficiencies as they often quote their "efficiency into fermenter" which is much lower than mash efficiency.

I still can't find a universal definition of "brewhouse efficiency" and the software out there doesn't help much. I even did several polls on what people mean by brewhouse efficiency. The distribution of results was frightening .

For this reason, I think it is a good idea that when brewers quote an efficiency figure, they also explain at what stage of production they have measured their efficiency i.e use the same terms as used on Sheet 4 of The Calculator.

I think that End of Boil Efficiency is perhaps the best one for brewers to quote where possible as bitterness and original gravity are 'final' at this point.

Thanks again Ralph,
PP

Good work Pat, lays it out in an easily understandable way.