Overnight mash

[Chrissyr63]

Hi all,

I am considering doing an overnight mash to try and save some time on the brew day.
My setup is a converted cooler box which I would cover in a few layers of hotwater cylinder jacket pads. During a 60 min mash tend not to loose much temp when I do it of a day time. This will be mashed in a large (insulated) wooden outbuilding which now that the winter in starting probably be <10c and maybe less overnight.
I usually do the standard mash 60 mins, drain, sparge stir wait 15 mins drain, sparge stir wait 15 mins drain routine using about 75-80c water (although maybe it is not so standard going by one of the other threads).

So my question is - is there anything different that I need to do? I assume the mash will have lost more temp and absorbed more of the first water.
So do I need to mash thinner (say 3 parts water instead of 2.5)? Need more recirculation to clear this?
Do I need to use hotter water for first sparge to bring the temp back up?

thanks,
Chris

[squantrill]

I left some brews mashing overnight and notice taste improvement leave for the normal mash time checking temp then after about 1.5 hours leave it..overnight easy ;)

[Charles1968]

I would start a couple of degrees higher than normal, do a much thinner mash (the greater the volume of water, the better it will hold temperature), and use masses of insulation. Start early in the morning. If you mash with enough water, you'll barely need to sparge. Ordinary sparge temp is fine. This system works really well and temp will drop 8-10 Celsius overnight if you insulate well. You need to stop it falling 20 or more as bacteria will then start to sour it.

[scuppeteer]

Start early in the morning.

Err.. did you read the post?

[Charles1968]

Start early in the morning.

Err.. did you read the post?

You've misread my post.

After mashing overnight, you continue in the morning. You need to start as early as possible or the temp will eventually fall to the point at which bacteria start multiplying. When I do it I typically dough in at midnight and then collect first runnings around 7.30 a.m.

[mark4newman]

Hi

I've done many overnight mashes in the past. Although I don't do it now*

The key is having a mash tun that loses little heat. After an hour and a half all the enzymes are denatured, so nothing happens to the fermentabilty of the wort. (Some people think it does, from my experience and understanding I disagree). So it just sits there until you are ready to use it.

Beer spoiling bacteria, don't survive a mash very well, and most are killed at above 60C, If your mash drops below about 55C, then this might start to cause off flavours in your beer.
So if your mash tun losses 1C per hour, and you mash at 68C, then try to come back to it in 8 hours or certainly before 13 hours. I use to mash at about 22.00 hours, and get up at about 7.00 hours (My mash tun losses about 0.75C-1C per hour)

You will also need to take notice that when you come to sparge, you mash will be a few of degrees cooler than normal, so adjust the sparge water to compensate. IE it will need to be hotter than normal.

Also, I found my efficiency was slightly higher.

HTH

* I don't do it now, as I have the water at temp when I wake up, so then start the mash. Take the dog for a walk, and then come back and do the boil. Basically I have filled the hour that I use to sit around!

[Charles1968]

I've also read that the enzymes are denatured after about an hour, but there's an experiment on braukaiser.com that suggests they keep working for several hours, though with diminishing returns. Higher efficiency also suggests they keep going after an hour.

[jaroporter]

The key is having a mash tun that loses little heat. After an hour and a half all the enzymes are denatured, so nothing happens to the fermentabilty of the wort. (Some people think it does, from my experience and understanding I disagree). So it just sits there until you are ready to use it.

assuming you start the mash at a temperature above the denaturation temperature for beta-amylase (say 68C).. a mash that spends a good few hours in it's optimum range is gonna give a very fermentable wort. i've had final gravities down at 1,001-1,003.

[Mr. Dripping]

I can only echo what jaroporter said there.
I used to do overnight mashes to try and save time but I was getting final gravities that were far too low.

[Charles1968]

Mine have finished 1010-1012 but I start the mash a couple of degrees higher than normal.

[pantsmachine]

I strew (good word) a couple of handfuls of hops across the mash once doughed in and genuinely see an improved heat retention in the mash tun. I use an igloo cooler and there is a temp probe in the mash through out. Overnight mash is the bollocks and breaks the brewday up wonderfully. I also find i will recirc for longer on day two during sparge and also post boil than if i try to cram the whole thing into one day.Makes it a more luxurious fun time than a slightly frantic 'Christ i have been at this 6 hours already' time.

[Charles1968]

Agree with pantsmachine about time saving. If you also skip the sparge by mashing in full volume or nearly full volume you can cut the brew day to 2-3 hours easily.

[Chrissyr63]

Hi All,

thanks for the info.

So if I use as much water as I can at a slightly higher temp and not wait too long I should be OK. Then sparge a bit hotter to add back the heat.
The recipe (and Old Ale from Greg Hughes book or possibly the OP from Graham Wheelers) I want to do takes about 5.5 kg grain and my cooler is a 23lt so should be able to get >15lts in (so a 3+ ratio). This should leave me enough to do at least a 10lts sparge just to wash everything out in the morning (will recirculates both).
Previously I've noticed my mash looses <1c after an hours mash but that is in much warmer weather (and the nights will be colder still) I can wrap it up a bit more also. Was going for an initial 68c should this be upped to 70c or just assume I have started a bit high anyway? So if it does all go below 55c is it a throw away job then?

thanks,
Chris

[Charles1968]

I would start at 70 Celsius. You can probably fit 20 litres of water in. The more water in the mash, the less the need to sparge. BIAB brewers mash in the full liquor volume and skip the sparge altogether. (The only point of sparging is to increase efficiency; otherwise it's completely pointless.) Your water volumes don't add up to a brewlength of 23 litres so perhaps check your maths if the recipe says 23 litres?

It wont drop below 55 - should end up 60 to low 60s. I think it needs to fall under 50 for a significant period to sour. Use lots of insulation - duvet, coat, anything you have to hand.

[Chrissyr63]

Hi Charles,

was going to work out the volumes on the day. I assume I'll loose +6lts to the grain (not sure with such a long mash) so would adjust my sparge water volume to try and get to 27-28 which just fits my boiler ie if I put 20 in as you suggest I expect 12-14 out and then need 16-14 added. Then loose about 4+1+1 to boil,hops, and dead space which gets me in the 22-23 ball park (or at least has in the past). That has been how I have calculated my lengths previously. If I miss the 23 I sometimes use bottled water to top to that. Sometimes just leave and hope for a higher abv . From some of the replies people expect I will go lower than 1.010 so might play safe and add the water.

As you say will put as much insulation as I have.

Chris