The Efficiency Question in a GF.

[aamcle]

I have an early Manual GF and I'm considering using it for some small higher gravity batches, small enough that I could brew full volume/no sparge.

The GF's efficiency is low with that sort of batch simply because there isn't enough sparge water to effectively flush the grain.

The plan would be to use a voil over the bottom plate or my very old abused Biab bag rather than the GF tube/plate overflow setup.

Working it out in the GF.

Dead Volume.........................3 litre
Grain Absorption ..................5 litre (assuming a grain bill of 5kg)
Boil Off..................................3 litre (90mins)
Vol into FV.............................12 litre
Total......................................23 litre water require (approximate)

If I allow for the water displaced by the wet grain it would be around 26 litre of space taken up in the GF which would be quite manageable.

Assuming that I use finer ground grain and get the pH/water treatment right what sort of efficiency might I reasonably expect?

Atb. Aamcle

 

[AlexKay]

I have nothing useful to say, except that I read this and was very confused about why one would worry about a girlfriend’s efficiency. Plus, reference to a “Manual GF” is kind of alarming.

 

[aamcle]

Simple an efficient GF irons your shirts! and reminds you in time for family birthdays.

 

[madscientist451]

Assuming that I use finer ground grain and get the pH/water treatment right what sort of efficiency might I reasonably expect?

Atb. Aamcle

Not sure if your water treatment is going to make that much of a difference, but if you are using a BIAB bag, you could use a bucket for a dunk sparge.

 

[aamcle]

If I have to sparge I may as well just use the GF will all itx metal work.

 

[doug293cz]

I have an early Manual GF and I'm considering using it for some small higher gravity batches, small enough that I could brew full volume/no sparge.

The GF's efficiency is low with that sort of batch simply because there isn't enough sparge water to effectively flush the grain.

The plan would be to use a voil over the bottom plate or my very old abused Biab bag rather than the GF tube/plate overflow setup.

Working it out in the GF.

Dead Volume.........................3 litre
Grain Absorption ....................5 litre (assuming a grain bill of 5kg)
Boil Off................................3 litre (90mins)
Vol into FV.............................12 litre
Total...................................23 litre water require (approximate)

If I allow for the water displaced by the wet grain it would be around 26 litre of space taken up in the GF which would be quite manageable.

Assuming that I use finer ground grain and get the pH/water treatment right what sort of efficiency might I reasonably expect?

Atb. Aamcle

Given the above parameters, the best you can do is 70.8% mash efficiency (100% conversion efficiency * 70.8% lauter efficiency.) If you don't get 100% conversion efficiency, then your mash efficiency will be lower.

Your brewhouse efficiency will be mash efficiency * 12 L / 15 L, or 70.8 * 12 / 15 = 56.6% (best case.)

Best case pre-boil SG is 1.058 and post-boil OG 1.0695 (this assumes a weighted DBFG potential of 80% for the grain bill.)

Calculation done with my spreadsheet.

Brew on

 

[aamcle]

Not so good, the lost to the wort retained by the grain bites...

 

[doug293cz]

Not so good, the lost to the wort retained by the grain bites...

Long drain times and/or squeezing a BIAB bag can reduce the grain absorption by 50% or more, thereby increasing your lauter efficiency. Leaving less wort behind in the BK will improve your brewhouse efficiency.

If you squeezed the bag down to 0.5 L/kg grain absorption, your lauter efficiency would increase to 78.5%, and OG to 1.077.

An equal run-off volume dunk sparge, at the original 1 L/kg absorption, would increase your lauter efficiency to 79.6%, and OG to 1.078.

Doing both a sparge, and a squeeze to 0.5 L/kg (for both initial and sparge drain) would give you 87.5% and 1.086.

Brew on

 

[aamcle]

I would struggle to get a decent Quad or big Sason out of that.
I have tried reiterating mashing twice on both occasions the efficiency wax very poor . With one batch I even adjusted the pH before the second mash, the specter of DME is looming large err maybe mmmm I believe I have forgotten they use candy sugar

 

[doug293cz]

Reiterated mashing really does nothing for efficiency. It's for solving the problem of not having a large enough mash vessel.

It's the nature of "big" beers. You cannot get really high pre-boil SGs and high lauter (and thus mash) efficiency (unless you have a real grain press.) This is why brewers came up with the partigyle process. You make one big beer with horrible lauter efficiency, and then rinse (sparge) the retained sugars out of the grain to make a smaller beer, thus not wasting so much grain/sugar.

Brew on