I've heard quite a few times that the more space you have below your false bottom the lower your efficiency will go but I've never heard an explanation as to WHY this is true or what the ideal amount of space below the false bottom is.

Is this a simple case of the less space below the false bottom the better? -If this were the case I'd assume that commercial false bottoms would have basically NO space below them and this simply isn't the case.


Does anyone know WHY you supposedly get less efficiency with a larger space below a mash tun false bottom?


Adam

Well if you think about it you are leaving lots of potential "runoff sugars" from the sparge in your dead space below your mash tun. But if you have a refractometer you should easily be to collect enough runoff to reach your desired efficiency and hit your OG.

If you have a dip tube or a bottom-draining mashtun (like most professional mashtuns) liquid left behind underneath the false bottom won't be an issue, so this has to be about something else, right?


Adam

Interesting topic. I've not heard that, or at least don't remember hearing it.

Holding that it is true, could it be that there is only a single variable in that theory and it is the dead space below the false bottom? If so, it is a function of the volume of water and grain being the same, therefore mash is effectively thicker when the false bottom creates more dead space.

In other words, you have 20 lbs of grain and 8 gallons of water. If your dead space is 1 gallon the mash is effectively thinner than if you had 4 gallons of dead space. Thinner mashes are supposed to be more efficient.

I'm not sure I could explain the theory in another way, and its just a wild-assed guess anyway.

~widget

-This is EXACTLY my theory too. Fairly early in the mash the enzymes migrate from the grain kernel's aleurone layer into the mash liquid and I'm wondering if they then just sit in the space under the false bottom unable to convert any starches because they're not in physical contact with the grain at that point.

Apparently thinner AND thicker mashes are less efficient beyond a certain point; it's that nice middle road that we want.

-I wonder if this changes when the wort is kept in constant motion ala a HERMS or RIMS mash.
I own a few brewing text books and I haven't come across a justification for WHY mashes with a greater space under the false bottom are supposedly less efficient. -I also haven't seen any brewery engineering recommendations for the percentage of the mash that SHOULD reside below the false bottom in an ideal situation; this is really what I'm looking for at the end of the day.


Adam

I think you mean your HYPOTHESIS...




Those enzymes that are in the liquid in the dead space, if in a still mash would not be in contact with the grains, but would be able to convert any starch that was carried down there with them.

I'd rather not roll out the jump to conclusions mat...

Not sure what you mean by that...


I don't have an answer regarding the efficiency issues you brought up, hopefully someone with experience with these type systems can chime in... you could also submit this question to Brew Strong and get JZ and Palmer's take on things too...