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Home Brew Forums > Home Brewing Beer > All Grain & Partial Mash Brewing > Big grain bill, undershot OG and lower efficiency
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Old 09-05-2012, 01:09 PM   #1
Monkfish
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Default Big grain bill, undershot OG and lower efficiency

Hi all,

Question for you - I recently did a Breakfast Stout clone from BYO mag and missed my numbers by a fair amount. 6 gallon batch and my biggest grain bill by far.

Using my cooler MLT I was able to fit all of the below in with about 1" of space between the top of the mash and the lid
.037" gap in my mill. Mashed at 156* for one hour (held temp) with 6.9 gallons of water after stirring like hell - no doughballs.
Batch sparged with 4 gallons of 175* water (BYO Mag called for that high temp.)

I had been getting 82-82% efficiency of late with IPAs (smaller grain bills) and generally hit my pre boil gravity numbers, but with this large grain bill I
ended up with 77%. My pre-boil gravity was 1.071 (stirred well before collecting), while I was expecting 1.082.

I'm not concerned so much as I am interested why my efficiency would have dropped / undershot my pre-boil gravity when my process largely remained the same.

The only change to my process was that I added 4.5g baking soda to the mash water to bring my bicarbonate level from 50 to 203 ppm and sodium from 12 to 68 (before this I'd never adjusted my water.)

4.50 g Baking Soda
9.6 oz Rice Hulls
15 lbs 13.4 oz Pale Malt (2 Row) US
1 lbs 10.4 oz Oats, Flaked
1 lbs 3.2 oz Chocolate Malt
14.4 oz Roasted Barley
10.8 oz Carafa III
8.4 oz Caramel/Crystal Malt -120L


Any thoughts you guys have would be appreciated.

Thanks
MF


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Old 09-05-2012, 03:06 PM   #2
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If your target was 1.082 and you got 1.071, even your normal 82% efficiency wasn't going to get you there. That being said, that grain bill is pretty big, and I don't think you even got 77% efficiency if you only hit 1.071. Maybe 60%.

It's pretty common to get worse efficiency with a big grain bill like that. You may have been better off with an extra sparge and boiling your volume down to meet the OG you wanted.


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Old 09-05-2012, 03:33 PM   #3
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I'm figuring out how to improve my <1.060 beers as well as get a decent extraction on a big one I'm planning. I use a 10 gal cooler MLT, so I do have the advantage of plenty of room to work. I read the big threads for several hours yesterday (at work of course) and came up with a few tips that should help you too.

1) Sparge with hotter water. I've been using 168º because Beersmith said so. Many folks use 185º. Point being, hotter water extracts better, and if you think about the temp and thermal mass of the MLT and grain, it shouldn't get over 170º.
2) Some use a mashout for the specific reason of increasing mash temp before sparging. Others say it won't impact efficiency.
3) It appears that the best extraction comes from splitting the sparge water into 2 equal volumes and sparging after draining the mash water from the tun.
4) This one I can't believe I didn't know before- after adding sparge water, stir the freakin' thing then vorlauf and run off as usual. (I picked up faulty info and mixed fly sparge techniques with batch sparging in my mind, and wasn't stirring)

That's it in a nutshell, I bet these things will help both of us get closer to the target.
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Old 09-05-2012, 04:59 PM   #4
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I get lower efficiency on large grain bills too. It's normal. To compensate, I usually Sparge more and boil longer. Some really big grain bills I get around 8 gallons of wort and boil down to 5. As long as your sparge runnings are above 1.010 your ok.
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Old 09-05-2012, 07:49 PM   #5
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4.5 g of baking soda will cause the pH of your mash to rise; depending on what you started with, this could cause a lower efficiency (as well as off-flavors).
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Old 09-26-2012, 12:45 PM   #6
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Thanks guys very much for the feedback. Yeah, this was my first foray into a really big grain bill, so the info above is helpful.

(I had posted a response a few weeks ago but it looks like it didn't take - likely user error.)
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Old 09-26-2012, 09:38 PM   #7
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So...did you hit your numbers? Did you identify anything that could be done better? Inquiring minds and what not I'm only a couple weeks away from brewing my winter ale.

I'm afraid "sparge more, boil longer" is going to be necessary for me. I was thinking of collecting wort in an additional pot and adding it to the big pot as it boils off or putting it on the stove inside. (I can only boil about 6.5gal, maybe a bit more with Fermcap-S). The LHBS might just have a nice new mill by that time, which would hopefully keep me in the 70% range with a good crush.


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