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Subject: Overnight Mash
Author: snappy
Jan 4th, 2008
12:42 am
Anything special to consider with an overnight mash? Should I be mashing a little warmer?
Subject: Re: Overnight Mash
Author: mroakley
Jan 4th, 2008
12:52 am
I'm sure it's obvious...but what are the reasons one would want to do an overnight mash?

If I'm slow smoking say a Boston Butt or brisket, that takes 8 hours, I can see a reason to do an overnight smoking. But a mash that takes an hour or two?

Maybe if you don't have a four to seven hour (however long your typical brew day is) stretch in one day?
Subject: Re: Overnight Mash
Author: CNYBrewing
Jan 4th, 2008
1:15 am
I mashed over night once and it turned out pretty good. Way out of range for color but it still tasted good. I was doing a pale ale and wanted to brew that night but fatherly duties took me away to take care of a sick child so I kind of forgot about it till morning when I woke up with a warm sweat and raced to the brew room. The pale ale became a dark ale but I think I took every ounce of sugar out of those grains.
Subject: Re: Overnight Mash
Author: brewsci
Jan 4th, 2008
2:00 am
I have done a few overnight mashes. In my experience, most of your conversion will occur as normal in the first hour or less. That is to say that grain will convert most similar to your starting temperature, not your ending temperature.

I would NOT suggest mashing warmer than you normally would because it will change your beer. The ROT is that you don't want the wort to drop below 140F or you can get baacteria growing that will sour the beer. In practice I have done 8-10 hour overnight mashes and never had a problem even though one got down to 135F. The temp drops 1-2 degrees and hour in my cooler, less if there is more grain and water in the cooler. You might want to mash at around 1.5qts/lb so you have more mass at your mash temp which will hold temp better. Only other thing is that I usually get better efficiency by around 5% and my vorlauf (C&E batch sparge) is typically very very short, less than a quart. Oh and you might want to heat your sparge water a little hotter if you are batch sparging since you will have lost a few degrees while mashing.

Time saved for me is up to 2 hours on brew day since I don't have to wait for the strike water to heat. It is convenient for me to start heating strike water, put the kids to bed, grind the grain, and mash overnight. Then I start heating the sparge water, make some strong coffee to drink while varlaufing/sparging,FWHing etc.
Subject: Re: Overnight Mash
Author: sberg
Jan 4th, 2008
5:38 am
I'll second what brewsci said about NOT raising your initial mash temp. That's what determines the beer not the ending temp.

I've recently begun long mashes to fit in with my family schedule. Mash before dinner and sparge after the kids are in bed with no ill effect. I do have amazing insulation on my MT though, and don't lose heat very quickly. I've gone up to 6 hours without noticing any strange results (up to 3 hours without a drop in temp so not exactly what you are asking). Make sure your strike water is at a good hot temp though. If you're too worried about temperature drops add a few blankets and cut it down some more.
Subject: Re: Overnight Mash
Author: halowords
Jan 4th, 2008
1:38 pm
"I'll second what brewsci said about NOT raising your initial mash temp. That's what determines the beer not the ending temp."

My understanding is that the rationale behind mashing a bit higher was that, due to the insanely long mash, the enzymes at work process the sugars and starches down more than in just a standard one-to-two hour mash thus resulting in a drier beer. Not really arguing any point, just wondering which theory is accurate.

-Cheers
Subject: Re: Overnight Mash
Author: brewsci
Jan 4th, 2008
5:35 pm
My experience with overnight mashing is that you tend to get a higher efficiency (and thus a higher OG if you do not adjust your volume), but that your FG does not change (unless you dilute). There should be plenty of unfermentables left. My last batch was an overnight mash at 155F. After 8 hours the temp was 148F. My tun is a well insulated cooler, but the temp was around 145 F on the very edges, but 154F in the middle. OG was 1.082 and FG was 1.020 with a US-05 yeast cake at 64-66F.
Subject: Re: Overnight Mash
Author: sweetloaf
Jan 4th, 2008
5:56 pm
that seems like high attenuation for a 155 mash, lending credence to the theory that you should raise a couple degrees (that is, your results more closely resemble a standard-length 152-153 mash). of course only a side-by-side would prove it one way or the other.
Subject: Re: Overnight Mash
Author: brewsci
Jan 4th, 2008
6:02 pm
Yea, but is was a full fresh yeast cake, about 75% AA. I think though that it is more that the FG doesn't change (and mouth feel unfermentables etc) and that the increase in attenuation is from better efficiency and a higher OG. My point is that I don't end up with a drier beer, just a slightly more alcoholic one.
Subject: Re: Overnight Mash
Author: sberg
Jan 4th, 2008
10:39 pm
From what I understand mashing on the high end of the scale, say 155-158, will shut down the enzymes that work at the lower temps so you will end up with a less fermentable beer no matter how low the mash ends up. Conversely, if you were to mash at the lower end of the scale, say 148-152, initially, you would end up with a much more fermentable wort even if you only maintain that temp for a couple of hours.

That's how it has always worked out for me no matter the length of the mash. But what I'm talking about is the FG not the OG. You very well might find that you have a higher than expected OG but not so much that it will really affect you. Maybe something like .005 points or something.

No matter how it works out you should treat it like a normal mash. Just my $.02. Good luck.

Cheers.
Subject: Re: Overnight Mash
Author: sparkalloid
Jan 4th, 2008
11:02 pm
its been my experience that, all other things being equal, a longer mash will raise fermentability slightly. when i make really big beers i always mash for a really long time - not for the sake of efficiency, but because i think that it creates a more fermentable wort.

ben
Subject: Re: Overnight Mash
Author: brewsci
Jan 4th, 2008
11:24 pm
I agree with Sheldon. The increase in OG for me on the last brew was around .008 or about 10%. My FG seems to be determined by the original mash temp. I also agree with ben that it makes sense that a longer mash would increase fermentability. But my experience has been that a longer mash doesn't really change the fermentability much. Maybe it is because todays malts are so well modified that almost all the conversion occurs quickly.

I think the overriding theme is that an 8 hour mash isn't that much different from a 60-90 minute mash. I wouldn't change anything, see how it turns out on your system, and let us know your results.
Subject: Re: Overnight Mash
Author: gillbates
Jan 5th, 2008
12:10 am
Even when I mash at 145, which I consider about the lowest practical, I'll get full conversion in under an hour. It wasn't until I bought iodine and started testing for conversion that I realized a 90 minute mash wasn't doing much for me.

My last batch had full conversion after 40 minutes at 145. Of course, I also had a 20 minute protein rest at 135, so the enzymes probably started working, at least in part, then. But 60 minutes total, and I just couldn't get any color change.

I have read that excessive temperatures and long mash times may extract more tannins from the grain. Let us know how the finished brew turns out.
Subject: Re: Overnight Mash
Author: mroakley
Jan 5th, 2008
12:20 am
I've heard the same thing about high temps, but aren't tannins a concern only if mash pH is out of whack?
Subject: Re: Overnight Mash
Author: sparkalloid
Jan 5th, 2008
12:37 am
as far as i understand, even when conversion is complete, enzymes continue to shorten long sugar chains into shorter ones, effectively making for a more fermentable wort.
Subject: Re: Overnight Mash
Author: gillbates
Jan 5th, 2008
2:43 am
Well, the batch I mashed at 145 for 40 minutes is just finishing up now at 1.016. It started at 1.063

I hadn't thought about the breakup of the heavier sugars, though.
Subject: Re: Overnight Mash
Author: brewsci
Jan 5th, 2008
2:54 am
Here is some good info on alpha and beta amylase, the enzymes that convert the starch to maltose.

http://www.allaboutbeer.com/homebrew/proteins.html

Seems like they both get to a point where they cannot break the starch down anymore (branch points), thus leaving unfermentable starch which contributes to body/mouthfeel
Subject: Re: Overnight Mash
Author: sberg
Jan 6th, 2008
7:07 pm
In regard to the FG depending on temp, I just took a gravity of a Pale Ale I made on X-Mas, which had a OG of 1.060. I had screwed up the strike water temp and wasn't able to raise the mash temp higher than 146F. The FG is 1.007. I was expecting 1.015 or thereabouts so I'm putting the results down to the low mash temp.

Kind of the opposite of what this thread was about but just an indication of how mash temp can have an effect on FG.
Subject: Re: Overnight Mash
Author: dpalm
Jan 14th, 2008
2:32 am
Based on this thread, I did an overnight mash this weekend. I mashed in an oatmeal stout (22 1/4 lb grain bill) at 155 deg F at 9:30 pm Friday night, put a foil-foam insulated jacket over my cooler, then piled fiberglass wool insulation around that, then blankets over the top to hold it all in place. I hit the sack and checked it again at 6:30 am the next morning--temp was still 142 deg F, with an overnight ambient temp of 22 deg F. Not bad. It definitely helped out my brew day, with everything in the fermenter and cleaned up by 11 am. I'll post again when I get an FG and try the beer.

Thanks for the great tip!
Subject: Re: Overnight Mash
Author: Chaselakebeer
Jan 14th, 2008
3:15 pm
Last Wednesday night a buddy and I did the mash and sparged and ran it off. Heated it to 160 then covered it and left it untli AM. Then we boiled and cooled and were cleaned up in about 3.5-4. It helped split a long day into a couple short ones.

This is awsome for me and I intend to do it again.

CLB
Subject: Re: Overnight Mash
Author: DavidS
Jan 14th, 2008
3:50 pm
I've got to try this sometime.
Subject: Re: Overnight Mash
Author: brewsci
Jan 14th, 2008
4:07 pm
Has anyone gone as long as 12 hours for mashing?
Subject: Re: Overnight Mash
Author: tripel666
Jan 14th, 2008
4:46 pm
brewsci - I just made a Tripel this weekend. I mashed 14 hrs over Friday night. Finished my batch before lunch on Saturday. I usually overnight mash my beers, which are usually belgian. Never a problem, good efficiency and good TG.
Subject: Re: Overnight Mash
Author: jmo
Jan 15th, 2008
4:59 pm
I'm with you, Steve . . . breaking it up like that turns what might have not been a possible brewing day into 'chapters' of brewing fun. I'll often start the mash over my lunch hour and finish the brew after work.
Subject: Re: Overnight Mash
Author: covertbrewing
Jan 22nd, 2008
5:12 pm
Hi All,

After reading this thread, I did my first overnight mash this past weekend. Mash time was about 7 hours. Efficiency went up by 12%. I prefer to brew in the evening... I was wondering if I started the mash before I went to work if a mash time of 11-12 hours would be too long ... maybe turn sour?

As always your input is appreciated.

Thanks,
Tim
Subject: Re: Overnight Mash
Author: brewsci
Jan 22nd, 2008
5:16 pm
From what tripel666 said , doesn't seem to be a problem. ROT is that bacteria that make it sour don't start working until under 140F. I haven't had any problems. I think you will be fine.
Subject: Re: Overnight Mash
Author: dandbrew
Dec 25th, 2008
5:29 pm
I attempted my first overnight mash this September and posted my results on youtube:

http://www.youtube.com/watch?v=kQLe47KN-dc

Benefits: shorter brew day, somewhat increased efficiency.

Next time, I want to start at a lower temperature, and slowly raise it throughout the night.

DanD
Colorado Springs, CO
Subject: Re: Overnight Mash
Author: dkubarek
Dec 26th, 2008
12:48 am
If you're just looking for a shorter brew day, I do this a lot now that I have a kid. I mash in, put the kid to bed, mash out, sparge and pasteurize. Just leave everything in the vessel overnight and begin boiling the next morning. You use a bit more fuel, but it's a great way for all-grain brewing without sacrificing any family time. I find the boil, cool, pitch phase to be the least labor intensive, so that's why I do that at night. Other methods, say mashing in the morning and boiling at night would be fine, too. +1 on getting the mash below 140 and +1 on an overnight mash being about the same as a 90 minute mash.
Subject: Re: Overnight Mash
Author: hankus
Dec 29th, 2008
8:27 pm
We need to know
- how long was "overnite"
-what the temp drops were and
-what was the ambient temp
which I suspect are the major variables...which brewsci was kind enough to share...what about more details please from the other advocates of prolonged mashing
Subject: Re: Overnight Mash
Author: dandbrew
Dec 30th, 2008
5:51 am

When I did my Saison d'Hiver Infernal, I stabilized at 148 F at about 10:00pm.

By morning, about 7am, I had dropped to 146 F.

So, "overnight" was in this case 9 hours with a temperature drop of 2 F.

Ambient temperature was about 68F, but I also surrounded the mash tun with 4-5 2-liter soda bottles with boiling water, then wrapped the mash tun with wool blankets. So, ambient temperature could be considered about 100 F? Hard to tell.

Dan
Subject: Re: Overnight Mash
Author: hankus
Dec 31st, 2008
5:02 pm
On further review,seems like an electric heating pad on the tun and then a wrap with a blanket ought to work well...i've enjoyed this thread but still don't expect I will adopt this approach...I suspect that the usual hopur mash time could be used for heating strike water, setting up stuff and the boil could begin after the first runoff so there really isn't that much down time.
Subject: Re: Overnight Mash
Author: dandbrew
Dec 31st, 2008
5:59 pm
An hour mash is great for most beers, but for an extreme all-grain, I would go this route again, or the oven mash just to ensure the most conversion possible.
Subject: Re: Overnight Mash
Author: hankus
Dec 31st, 2008
6:48 pm
...dandbrew,a point well taken

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