[spurviance]

In order to break up the time required for brewing all-grain I started performing overnight mashes in lieu of traditional 60 minute mashes last year after reading about a brulosophy experiment where tasters were unable to reliably distinguish the differnece between a pilsner brewed using these 2 methods.  I typically brew 5 gal batches using BIAB and have made some tasty beers using this method.  So far the only negative I've found using this method is my efficiency tends to vary from 75-85% using an overnight mash, compared to 70-75% using a traditional mash. 
I'm curious if anyone has had any problems doing overnight mashes, or any particular styles where this method didn't work as well.

[dmtaylor]

Fermentability/attenuation will be maximized for sure.  Expect attenuation to be about 10% higher than "normal" for the particular yeast strain.  You could compensate for this by selecting a yeast with known lower attenuation... or decide whether maybe you just don't care and don't need to adjust, that's cool too.

[KellerBrauer]

In order to break up the time required for brewing all-grain I started performing overnight mashes in lieu of traditional 60 minute mashes last year after reading about a brulosophy experiment where tasters were unable to reliably distinguish the differnece between a pilsner brewed using these 2 methods.  I typically brew 5 gal batches using BIAB and have made some tasty beers using this method.  So far the only negative I've found using this method is my efficiency tends to vary from 75-85% using an overnight mash, compared to 70-75% using a traditional mash. 
I'm curious if anyone has had any problems doing overnight mashes, or any particular styles where this method didn't work as well.

I have also read about this procedure.  But I’m curious, how do you maintain mash temperature with this method?  Unless you’re using an electric automatic system, a typical cooler would loose quite a few degrees overnight.

[dmtaylor]

how do you maintain mash temperature with this method?  Unless you’re using an electric automatic system, a typical cooler would loose quite a few degrees overnight.

Does it matter?  Most of the enzymatic activity is done in the first hour.  Remnants will continue to break down sugars very slowly over the next several hours, but this will happen whether warm mash temperatures are well maintained or not.

[spurviance]

Dave-  I have noticed a higher attenuation and to this point I've been rolling with it and accepted beers a bit stronger than planned.  I'm hoping once I get my efficiency numbers more consistent I can scale my recipes down a bit to compensate.  I will also look into using less attenuating yeast. 

[spurviance]

how do you maintain mash temperature with this method?  Unless you’re using an electric automatic system, a typical cooler would loose quite a few degrees overnight.

Does it matter?  Most of the enzymatic activity is done in the first hour.  Remnants will continue to break down sugars very slowly over the next several hours, but this will happen whether warm mash temperatures are well maintained or not.

I don't try to maintain my mash temp and accept it will drop overnight.  I'm mashing in my boil kettle and insulate it with a thermal wrap and a couple towels to keep the temp relatively stable during the first hour or so but by the morning the temp is usually between 110F to 120F depending on the time of year here in Northern California.  I usually mash in a couple degrees warmer hoping to enhance body a bit and compensate for time spent with mash at lower temps, not sure if it helps as my FG numbers are a bit lower than planned due to higher attenuation that Dave alluded to above.

[dmtaylor]

Dave-  I have noticed a higher attenuation and to this point I've been rolling with it and accepted beers a bit stronger than planned.  I'm hoping once I get my efficiency numbers more consistent I can scale my recipes down a bit to compensate.  I will also look into using less attenuating yeast.

[EHall]

I've been using this method for years and love it. mash into a cooler, go to bed and its only lost maybe 6-7 by morning.

[KellerBrauer]

Fascinating - and, apparently a greater amount of extract is produced overnight! 

[Robert]

Fascinating - and, apparently a greater amount of extract is produced overnight!

I suspect it's a matter of leaching more of it into the runoff, like slowing down the sparge will do compared with a rapid runoff.   No matter how you mash, you shouldn't be stopping the mash program until you have reached 100% conversion as confirmed by both wort density measurements and iodine test.   After that it's just lautering efficiency.

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[KellerBrauer]

Fascinating - and, apparently a greater amount of extract is produced overnight!

I suspect it's a matter of leaching more of it into the runoff, like slowing down the sparge will do compared with a rapid runoff.   No matter how you mash, you shouldn't be stopping the mash program until you have reached 100% conversion as confirmed by both wort density measurements and iodine test.   After that it's just lautering efficiency.

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Perhaps this question is for another thread, but you (Robert) mention iodine test.  I have read about this test, and, in fact, I’ve asked other brewers about it, but can’t get a good answer.

What is it, how does it work, what instruments/products are needed and how does one perform this test?

[Robert]

A small sample of the liquid mash (no solid particles) is placed on a white porcelain saucer.  A few drops of tincture of iodine are added.  Watch the interface between the two, looking for any change in color.  When iodine meets starch or other more complex carbohydrates,*  it will turn black, blue, deep mahogany, etc. depending on the degree to which the carbohydrates have been broken down.  Black or blue indicates a lot of native starch.   No color change at all, the dilute iodine still showing a yellowish color, indicates complete conversion, all the starch turned to sugars.  This is called a "negative iodine test" and is your goal.  At this point you can mash off and collect the wort.  You can, I say.  But conversion is not the same as extraction:

Tracking density is easiest with a refractometer on our scale.  You can calculate the maximum wort density possible given your grain bill and volume of water,  and when that is reached you know you have not only converted starch to sugar, but fully extracted it into the wort.  That probably is a topic for elsewhere,  but both of these are discussed on the old Braukaiser website (though Kai has a rather wonkier version of the iodine test.)

*Including cellulose and the like, which is why you want to avoid solid particles of grain and husk in the sample.

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[KellerBrauer]

^^^^^^^^

Fascinating information.  I believe I have found the website you’re referring to.  I’m going to read up on the subject.  Thanks for your help!

[denny]

^^^^^^^^

Fascinating information.  I believe I have found the website you’re referring to.  I’m going to read up on the subject.  Thanks for your help!

FWIW , I found the iodine test so unreliable and uninformative that I stopped doing it many years ago.  Give it a try and decide for yourself.

[Robert]

^^^^^^^^

Fascinating information.  I believe I have found the website you’re referring to.  I’m going to read up on the subject.  Thanks for your help!

FWIW , I found the iodine test so unreliable and uninformative that I stopped doing it many years ago.  Give it a try and decide for yourself.

I gave it up but went back.  Maybe that's a bit belt-and-suspenders, but it's all information.  If you have to do only one test, monitoring first wort density is the one.  You won't get to maximum potential density without first achieving full conversion.  But in most cases we don't have sufficient lot analysis on all our grains to calculate the potential of our malt with absolute certainty, so the iodine test is insurance, as I see it.

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