How To Fix This Mash Problem

Do those 2 gallons end up being left behind in the kettle, or do they make it to the fermenter? If the former, mash efficiency is definitely suffering. If the latter, you simply have a narrower range of water to grain ratios to work with, and thus a narrower range of potential usable mash thicknesses.

 

If you could fill those 2 gallons with something, you would have a wider range of possible water to grain ratios to choose from. But, is there some reason you think there's a problem?

 

I don't think the extra space is casuing your efficiency problems, unless the effective mash thickness (where the grains are) is way too stiff. What does a typical batch look like, i.e. lbs of grain and strike water volumes? (not just the ratios, but actual numbers)

Are you batch sparging? What's a typical sparge water volume for the example above?

I can't think of a reason it wouldn't work. But let's see if there's a problem (with the space) first, or if something else is causing your efficiency problems.

 

Bear with me... did your lower efficiency happen to coincide with making bigger beers? With bigger beers, you leave more wort behind in the grain beds, so when you collect just enough wort to account for your standard boiloff and reach your 5 gallon (or whatever) target, efficiency suffers. One way around this is to sparge more and increase the boil time, but that's not ideal for some styles (though with a quad it would be fine).

 

It's worth a shot. The ratios of sparge water to mash water do matter (though usually marginally at practical volumes). I have looked at that in depth for batch sparging, but not for fly (which I don't do anymore). Another thing you might try is a slightly thicker mash (1.25 is not a lower limit), so that you can sparge more (even if not adding water requiring a longer boil). But I suspect the affect would be small. (You'd be rinsing more, but the viscosity of the wort you're rinsing would start out thicker, so the benefit is self limiting).

What kind of efficiency numbers are you getting now?

 

Why not just brew 15 gallon batches?

 

I should clarify this statement. It's not that there's more wort per se left behind, it's that the wort left behind hasn't been proportionally diluted to the same extent as with a smaller beer, because a smaller amount of sparge water has been used to rinse/dilute the sugars from a larger volume of wort.

 

Admittedly, I'm not the best person to be offering advice here, but...could you run off the 2 gallons beneath the false bottom first and then include that in your total sparge amount?

 

@ggroller - he wouldn't be able to really do 15 gallon batches anyway, the equipment has a total 15 gallon volume. 10 gallons would work though.

What I do think you need to do is fine a friend and start doing 10 gallon batches! But of course, you'll need to get that chilling situation figured out first I suppose. Sorry, I'm no help with the topic. I'll be leaving now.

 

Have you measured your efficiency?

If it is really a problem, you could replace your false bottom with one of these: http://www.austinhomebrew.com/produ...10654&osCsid=6c7795073b1f47fa0a369e5f29012f8b. That will not eliminate the space below the grain, but it will reduce it.

 

I use a converted keg and a false bottom for a direct fired kettle. My void space is about one gallon below the FB. I however continuously circulate the mash using a pump. As a result I do not account for that space as extra water in my qt/lb ratio. This is because the recirc effectively keeps all the starches, sugars and enzymes pretty homogeneous throughout the mash.

I would say that if you were to recirc a few times manually throughout the mash you'd be in good shape as far as getting what ever efficiency your system will provide (based on crush, pH, etc etc).
And the difference between say 1.25qt/lb and 1.6qt/lb shouldn't change your inherent efficiency much at all. If you really are having efficiency issues, I'd look closer at your crush first. And leave this 2 gallon void volume as a process issue to be resolved independent of your efficiency (to a degree).

 

Prop the back of your kettle when you are finishing up each of your runnings. The "don't disturb the mash bed" is a bunch of hooey!

Brew 15 gal and make more friends.