Space under false bottom - 1 gallon AG

[Dclubb83]

OK, so I recently made a small version of a "zapap" mash tun out of two 2-gallon buckets (drilling a bunch of small holes in the bottom of a bucket and putting it inside another bucket to act as a false bottom), as recommended by my LHBS as a good way to do one gallon all-grain batches.

I've found that there is 1.75 qt of space under the "false bottom." According to Mr. Papazian, you should mash with one quart of water per pound of grain, and sparge with twice that amount. So if a had a 2lb grain bill, that would call for mashing with 2qt of water. But if I were to put that in, 1.75 of those quarts would be below the false bottom. But if I were to make sure that 2 qts were touching the grain, and used 3.75 quarts to mash with, then, after the grain absorbs 0.8 qts(another Papazian figure), I'm left with about 3qt of first runnings.

So then I'm supposed to sparge (given my setup, it would be batch sparging) with 4 quarts, but if I also make up for the space under the false bottom, that would be 5.75 quarts of second runnings. Leaving me with a pre-boil volume of almost 9 quarts for a 4 quart batch.

Given my boil-off rate and trub loss and such, I need to have right around a 7qt pre-boil volume. So how do I make up for those 2 extra quarts? Mash with less? Sparge with less? Add 2 quarts of the first runnings to the sparge to get correct volumes on both?

Sorry if this has been covered, but I've searched for days and haven't found the answer.

Thanks guys

 

[McKnuckle]

Hopefully I'm not missing something in trying to follow you:

You only have to account for the dead space during the mash. I think you're on track here; you are making sure that the grains are covered by the minimum volume of 1 qt/lb of water, so you have 2 qts on top and 1.75 qts below the first pail, giving you 3.75 qts for the mash. The grain will absorb about 0.8 qts, leaving 3 qts exiting your pail for first runnings.

But when you sparge, you are rinsing the grain, not soaking it. So you don't care about accounting for the dead space again. The grains have already absorbed what they can absorb, so you don't double-count that either. In short, you sparge with 4 qts of additional water and collect all of it. You end up with 3 + 4 = 7 qts to boil with.

Make sense?

This being said, if it were me I'd mash with a higher ratio, say 1.5 qts per lb, which for a 2 lb bill would be 3 qts (4.75 qts total). You'll get 4 qts in your first runnings. Then sparge with 3 qts. But any way you do it, I think that's how the math and losses would work. I think the mistake you're making is thinking that the 1.75 qts in the dead space is meant to be discarded - not so at all! The sugar is draining into that water during the mash. You need to recover it.

 

[LandoLincoln]

As long as all the grain is covered by the mash water and then some to compensate for the grain absorption, you should be good to go for the mash. It is my (to my knowledge unproven) conjecture that the 1.75 quarts of water is not just sitting there under the grain doing nothing to contribute to the mash, so it should be included in the quarts-to-pounds mash ratio.

In answer to your question, you would sparge with enough water to ensure that you hit your target pre-boil volume. My advice is to make more sparge water than you think you'll need and just leave some in the mash tun once you hit your pre-boil volume.

If you have 3 quarts of first runnings and you need 7 quarts for your pre-boil, then you'd use 4 or 5 quarts for the sparge and then just stop collecting once you hit 7 quarts. I personally don't subscribe to the "sparge with twice as much water as the strike volume" belief. It's much more important to 1) make sure that the grains are covered in water sufficiently and 2) make sure that you hit your pre-boil volume.

 

[Dclubb83]

You only have to account for the dead space during the mash.
[...]
But when you sparge, you are rinsing the grain, not soaking it. So you don't care about accounting for the dead space again.

So actual water contact with the grains isn't important in batch sparging? If that's the case then that completely solves my problem. I figured that water contact was equally important in both mash and sparge.

 

[McKnuckle]

Water contact is certainly important during sparge, but with the volumes we're talking about, the dead space doesn't really affect it. There's still enough water up top to completely cover the grains before the sparge volume is drained. During the two runoffs, aren't you supposed to lift the top bucket so that the liquid can run out of the holes and into the bottom bucket? So what matters is rinsing the liberated sugars out of the grain, through the bottom holes, and into the bottom bucket. Stir really well and that will happen. Then you dump the bottom bucket contents into your boil kettle and proceed.

You'll get everything you started with except for the absorbed volume - which should be between 0.44-0.48 qts/lb. That's your only loss. So if you need 7 qts to boil with, your total water needed is between 7.88-7.96 qts.

 

[emyers]

Why not just BIAB? How large is your kettle?

 

[McKnuckle]

Actually with a batch that small, you can do a full volume mash in the kettle with NO bag. All you need is a second vessel and a strainer to catch grains when you pour out the wort.

 

[Dclubb83]

My kettle is actually only 8qt, which is an issue in itself, given that 6qt is just about my limit without boiling over. But I plan on just keeping one quart of the second runnings at a low simmer in another pot and adding that about 30 minutes into the boil to get my full volume.

And I was thinking of doing BIAB, but when the cost of both buckets for the zapap was $10 plus the $5 for the spigot on the bottom bucket, and the bag was $10, I figured my money was better spent on something more permanent.

 

[McKnuckle]

Actually you can easily use your little kettle to mash in without any bag or special apparatus. Just dump in the grain with the full volume of water. It's so little that you can pour it into another vessel through a strainer, no problem. Talk about cheap!

 

[Dclubb83]

I wish I would have thought of that before I made the zapap lol