Hi there LG
,
I've just got back from being away but in addition to your question above have read your thread
here. Some of what I write below might apply to that thread as well. It's been a long week and so I'm writing the below as much as a way of unwinding as in answering your question. In other words, please don't expect it to be short, written/re-written and edited a million times as I do with some other posts I do here
.
Point Number One - Available Data
When it comes to
extreme mash thicknesses, I don't have much personal solid data on "mash efficiency" and I don't think I have found any, anywhere else. (In fact, you won't find much info on even normal mash thickness mash efficiencies.)
When I talk of "Mash efficiency," I mean the efficiency at the end of the mash. In a full-volume BIAB, mash efficiency would equal your kettle efficiencies (Efficiency onto Kettle - EIK or Efficiency of Ambient Wort - EAW) but in a non full-volume brew that includes sparging, this is not true.
On a brew day here, a few BIABrewer members and myself did an identical recipe side by side. We full-volumed one and the other we mashed at a porridge like consistency (I'll dig up the thread when I get more time.) The weirdest thing was that the extremely thick mash had a
lower gravity reading than the full-volume mash. I would very much like to but don't have the time, keg space etc to repeat the experiment as the readings make little sense.
One thing I do know is that existing mathematical models we can find elsewhere on what gravities to expect from high gravity brews are not based on real data. They are based on extrapolations of a small range (or amount) of data. Worse still, brewing software (except for the BIABacus) pretends that you get the same mash efficiencies (and therefore all other efficiencies) from a very high gravity brew as you do from a very low one. This is very much incorrect.
From reading the other thread, I see that you have discovered the BIABacus's auto-efficiency formula. This and the warnings in the BIABacus are going to be your best friend when it comes to making decisions on what to do when you come across a situation where your kettle size is too small to do a full-volume mash.
Point Two - Full Volume if You Can
On the data we have collected here on several side by side brews and through BIABacus results from several members, the current advice is that you should always full-volume your brew if you can.
This advice will seem counter-intuitive, even ridiculous* to many brewers but it actually is totally logical. The data and explanations
are here on this forum but I don't write them in ever post I write here. If you want more info on that, just ask. It's probably time I had another bash at collecting the relevant links and writing another "washing machine" analogy. (Until I do, a search of, "washing machine", is bound to give some decent results.)
[*
Here is an example of me being quoted on another forum on non-sparging and then being described as having a "complete lack of credibility"
. It's a shame that I don't have enough time to devote here, in a quality way, let alone have time to answer posts like that on other forums
. All the evidence and answers are actually here on this forum but it is really hard to find them unfortunately
]
Point Three - I Can't Full-Volume
Have a read of this post
here.
Did you see the bit that said that sparging was almost always a waste of time, effort and equipment? Did you read the next section as well on how a sparge can save you? If so, that last thing is the main point relevant to your question here.
Point Four - Non Full-Volume is All About Juggling
I wrote above that the BIABacus will be your best friend. It will be. It should be able to teach you some things far faster than I can explain them. Your questions above can actually only be answered with the BIABacus and your conscious understanding.
If the BIABacus says your vessel isn't big enough for the brew, you need to consciously decide whether to lower your desired VIF, dilute or sparge. Eithr choice or combination of choice has costs. Only you can decide if the cost suits your situation.
The BIABacus will tell you if what you plan to do is ridiculous or impossible as it throws up a warning. (Careful though as from memory some critical warnings didn't work in some pre-releases). In your situation, you are getting close to being thrown a warning though as 57% EIK is very low.
...
Point Five - A Quick Answer to One of Your Questions.
LG, you asked above, "I wonder if simply pulling the bag and topping up the kettle would actually give me the 1.068 EOB-SG I'm shooting for?"
If you input this into the BIABacus, you will get an immediate answer/advice from the BIABacus.
Do this and then post your BIABacus file into that other thread you have going atm -
this one. I'm one of the guys that can say it is okay to post a BIABacus file in a certain thread so just mention you have been given an okay to do so. I think though that you doing so will probably force you to direct your attention to the right areas and maybe your questions here will become null and void? (The BIABacus is the only tool that will tell you if your gravity and volume plan is possible. All we can do is help you to understand how it works.)
Remember, when you stray from full-volume brewing, you enter a complete juggle. This is why existing commercial software has done okay up until now - the juggle disguises everything which makes everything very difficult to prove false or true.
BIAB shines a light on everything - there is nothing to hide behind.
The BIABacus goes further and can juggle the balls any way you want without defying the laws of "brewing physics" like other programs do. You, as a new brewer (or even an old one) don't need to worry about this. All you really need to worry about is if the BIABacus tells you that your brew volume/gravity plan is possible.
...
I'll leave it up to you to distill the above and ask what questions you need to
,
PP