Overnight Mashing

Get advice on making beer from raw ingredients (malt, hops, water and yeast)
Post Reply

Overnight Mashing

Post by Fingar » Wed Nov 04, 2015 8:55 pm

Hi Folks,

There have been a few questions asked about mashing overnight, however, I don't see anything recently so I was wondering if there were any more thoughts on this topic.

My thoughts, as seems to be everyone else who has thought of or done this technique, is that it saves a great deal of time - or maybe it just seems that way! Previous entries have asked if there have been any detrimental effects to the wort by mashing for an extended period... I tend to mash for 90 minutes, well, when I say 'tend to mash', I have only done 5 AG beers.

Is it indeed OK to mash overnight... does this extract any nasties?
So, assuming that it's OK to mash overnight, do I follow the exact same procedures for 60-90 minute mash temperature?
What about sparge temperature? Do I keep this at normal temperature or do I bump it up a bit?

BTW, my mash tun is a Coleman cooler which is great for insulation... it that does indeed matter.

Cheers... Fingar

Mr. Dripping

Re: Overnight Mashing

Post by Mr. Dripping » Wed Nov 04, 2015 11:28 pm

I have done some overnight mashes, but found my FG's were far too low as a result...you get more conversion in to fermentables and less dextrins. The beers were very thin as a result.
There is also the chance of introducing lactobacillus if the temperature drops too much and this will sour the wort.
I don't do overnight mashes anymore as I feel I get a much better quality beer from a 60 or 90 minute mash with a lot more control over the final gravity of the beer.

User avatar
Piss Artist
Posts: 142
Joined: Thu May 29, 2014 12:57 pm
Location: Chester

Re: Overnight Mashing

Post by DethApostle » Thu Nov 05, 2015 2:28 pm

While not overnight I now often do a over-work Mash of around 10 hours.
Mash in around 7:30am, go to work, and then sparge at 6pm once I'm home again!
Using a Thermopot as a MashTun I generally lose 2-3 C over the mash which isn't a problem at all. (Nasties only really become an issue if the temp drops below 50C)

I haven't noticed these beers being thinner or dryer than 'normal' mashing. Perhaps the FG's are slightly lower that the target Beersmith gives me... but I can't remember exactly if I'm honest!

Ultimately an overnight/day mash is a perfectly valid option which will still produce decent beer at the end of it! It's about being able to fit your real life around your brewing!
Brewery Build in progress!!!
Brewed in 2012: 200 pints
Brewed in 2013: 560 pints
Brewed in 2014: 360 pints
Brewed in 2015: 280 pints
Brewed in 2016: 320 pints
Brewed in 2017: 280 pints
Brewed in 2018: 320 pints
Brewed in 2019: 120 pints


Re: Overnight Mashing

Post by raiderman » Thu Nov 05, 2015 2:46 pm

If you are worried about thinness simply add some carapils which will over come the problem. Malted or porridge oats or malted rye could help too

Piss Artist
Posts: 173
Joined: Sun Apr 06, 2014 8:39 am
Location: Whitley Bay

Re: Overnight Mashing

Post by UpTheToon » Thu Nov 05, 2015 2:57 pm

I've almost exclusively done overnight mashes for my last 10 or so brews. Haven't noticed a drop in FG and beers still seem good. It certainly saves time on the actual brew day!

User avatar
Piss Artist
Posts: 255
Joined: Tue Jan 15, 2013 11:32 am
Location: South Cheshire

Re: Overnight Mashing

Post by PhilB » Thu Nov 05, 2015 3:00 pm

Hi Fingar

Have a read of the information there (link) it answers most of your questions ... and shows that ...
Fingar wrote:BTW, my mash tun is a Coleman cooler which is great for insulation... if that does indeed matter.
... yes, that matters :? ... and would probably help address Mr D's "problems", if he were of a mind to solve them :?

Cheers, PhilB

Mr. Dripping

Re: Overnight Mashing

Post by Mr. Dripping » Thu Nov 05, 2015 4:04 pm

I solved my 'problems' by (a) not mashing overnight any more, and (b) buying a BM :D
My experience has been somewhat contrary to what is discussed in your link.....I can only report what I find.
Simple fact was that IME, FG's were much lower than anticipated, beers that I would expect to finish 1010-1012 were going as low as 1005/1006. Same yeast....same initial mash temperature.
I never had a problem with lacto as the mash tun in my 3V system retains heat very well indeed.

User avatar
Piss Artist
Posts: 255
Joined: Tue Jan 15, 2013 11:32 am
Location: South Cheshire

Re: Overnight Mashing

Post by PhilB » Thu Nov 05, 2015 5:41 pm

Hi Mr D

To be clear, I put the word "problems" in quotes like that, because I was fairly sure you no longer found it a problem, and not because I don't believe those problems exist, in a brewing sense ... if Fingar has a go at overnight mashing he may well experience lower than expected FGs, like you did ... but following the advice in the link before/when he tries may reduce the chances of that happening, and he may not notice any changes in his FGs, as I have experienced and UpTheToon seems to have done too ... but then if he does experience lower than expected FGs, the link will give him advice as to what he may want to change to solve that problem :?

Who knows it may involve something cheaper (say a pile of old blankets) than a Braumeister :) :D :lol: :wink:
Cheers, PhilB


Re: Overnight Mashing

Post by Piscator » Thu Nov 05, 2015 6:31 pm

I did some overnight mashes a long time ago when I started brewing - the beers were okay, but I found that as I got more proficient at using my kit it really wasn't saving enough time to be worth worrying about. You still have to heat the mash liquor so that time is not saved - all you are saving is the time taken to heat the strike liquor and the time to mash the grain itself... however I heat the mash liquor while the mash is on so I don't "lose" much of the mash time if any. My normal routine nowadays is to get up reasonably early and get the mash on, prep and start heating the sparge liquor - then go and have breakfast while it all does it's thing. By the time I've had a nice fry up and cuppa the mash is done and the sparge liquor is ready - I'd say overnight mashing might save me about 40 mins on a brewday which just isn't enough to make it worth bothering with.


Re: Overnight Mashing

Post by BrewHouse » Thu Nov 05, 2015 7:46 pm

In my opinion, it is an absolute MUST to mash on brew day. I normally have some friends around to 'help out' on brew day which always involves some significant sampling of previous brews. If I had already completed the mash we would lose 3 or 4 pints worth of sampling time. That would never do! :D


Re: Overnight Mashing

Post by mark4newman » Fri Nov 06, 2015 1:50 pm


I overnight mash now, almost exclusively. I don't get any problems with it being overly fermentable, or anything else. I do get better efficiency, and a shorter brew day!

Prior to overnight mashing I did it for 90mins. Did the last brew at the weekend, and mashed in at 9pm at 66.5C, at 7.30am it was 61C ...got 77.5% attenuation, which is exactly the same, as before and almost bang on predicted by the software. I had brewing sugar in brew, so was higher and expected to be higher than the normal range for the yeast

I think the reasons I don't get a problem compared to others, is

1) I tend to do a thin mash which, which helps my mash tun holds temp very well. (3.5). IE you want to create a big mass to help hold temp. (I also warm the mash tun up with a kettle full of water)
2) I did 90mins mashes, rather than 60mins
3) It never gets anywhere near 50C which is the temp bugs can start to grow.

What I do get is better efficiency, partly because of overnight mash but aslo because of thin mash.

Anyway, like most things in brewing if it works for you , and it does work for me, then you are doing it right.


Re: Overnight Mashing

Post by SouthLondonBrewer » Fri Nov 06, 2015 8:11 pm

+1 mark4newman.

I nearly always do overnight mashes. Finishing gravities usually about 1010 (from OG around 1045), varies with yeast. No problem with overattenuation or thin beers and definitely never anything like 1006, unless making saison. Anyone getting that low has made a mistake somewhere else in the pipeline. Efficiency is a lot higher than 1 hour mash, which I suspect is because you get better extraction from any coarse bits of grain after the longer soak. Also probably because I mash thin like Mark to hold the temp up.

You need to do some prep previous day - plan recipe, treat water, measure out grain. I typically heat the strike water after 11pm Saturday night & then cover the mash tun with blankets. Having a coffee while taking first runnings is a great way to start the day. Quick batch sparge after draining the tun, then boil. Everything over by lunchtime.


Re: Overnight Mashing

Post by jimbothenav » Mon Nov 09, 2015 1:33 am

I mash in a very similar manner to SouthLondonBrewer and have done over 35 successful brews now and am quite confident in brewing overnight – it just fits with my domestic routine if nothing else.

I plan the recipe and weigh out the grains on a Saturday afternoon when I get a chance and prep all the kit (I brew in my garage – a much better use than keeping cars dry!)

I mash thin, using 18 litres of water at 72ºC strike resulting in 67ºC when the 4Kg of grain is added. I mash in a converted picnic cool box starting at 11pm and with plenty of blankets and old duvets end up at 8am the next morning with 57ºC. Never had a hint of an infection.

I trickle sparge with hot water at 90ºC (as opposed to 85ºC) to compensate for the final temp of the 18 Litres of mash being down at 57ºC.
Unlike SouthLondonBrewer I drink tea during the sparge – it may not make a difference!

It is all into the boiler by 9am along with hops and I then take the dogs for their exercise before needing to add the late hops at 10:20am - boil complete at 10:30am.

Chilling down the wort takes 45 mins and then transfer it to the fermenter, pitch the yeast and make myself available for further domestic duties by around midday.

Overnight mashing works for me :-)

Post Reply