BIAB mash temp issues.

[Strangelove]

Howdy,

I used a bread tie on the pot handle to hold my glass thermometer in the mash. I mashed in at 159 as instructed in Beersmith. The temp gradually dropped to 154 over 60 minutes on the stove with no lid. I took the pot back outside to the propane burner. I was to have heated to 168 over 7 minutes to mash out (I'm not sure this is even possible with 7 gallons). The temperature barely moved for ten minutes, so I gave the mash a stir. It then read 134! Cranked the heat even more. The glass read 150's and the digital read 190. There was a bit out foam forming so I gave up and mashed out.

The question is how do you read mash temps reliably? Glass? Digital? Mix and measure? In the middle of the grain?

Thanks.

 

[NordeastBrewer77]

i do BIAB, stovetop, and i use a floating dairy thermo in my mash. because of temp stratification, i have to stir the mash before getting an accurate reading.
mash temps are important; too high (over 156) and you get a lot of unfermentables, too low (below 145ish) and you don't get good conversion. way too high (over 165-68, you risk extracting the harsh tannins from the grain husks.

 

[Strangelove]

Do you stir periodically throughout the mash?

 

[NordeastBrewer77]

very very carefully, with the thermometer. i've read that it's not the best to stir too much, because of tannins and such, but my mashes vary so much from the top to the bottom of the grain bed since i'm mashing in a kettle. i just stir gently with the thermometer, let it sit for 30 seconds or so, then read the temp. i usually get pretty good conversion, 70% or so, and have never noticed off flavors from tannin extraction.

 

[plumbob]

I gently stir my BIAB brews every 15 min. Presumably you could get a mash that wouldn't have any conversion at the top or the bottom if you got it really stratified. So, they get agitated 4-6 times through the mashing. Once I've doughed in the grain and mixed it well the whole pot goes in my oven preheated to its lowest setting then turned off. I can usually hold the mash within a 3 degree window for 90min that way. I usually run about 75% efficiency.

 

[NordeastBrewer77]

I gently stir my BIAB brews every 15 min. Presumably you could get a mash that wouldn't have any conversion at the top or the bottom if you got it really stratified. So, they get agitated 4-6 times through the mashing. Once I've doughed in the grain and mixed it well the whole pot goes in my oven preheated to its lowest setting then turned off. I can usually hold the mash within a 3 degree window for 90min that way. I usually run about 75% efficiency.

totally agree, bro. that's exactly how i do it too. if you don't stir, parts of that mash get way to warm. and the 'oven on low' idea is great, especially if i'm only mashing >4#, as the smaller mashes don't hold temp for $h*t. i've gotten as good as ~80% efficiency doing BIAB like this.

OP, did you read DeathBrewers sticky on BIAB? it's really basic and VERY useful. makes it as easy as extract w/grains. :rockin:

 

[gunner65]

Yes you need to stir periodically. That is why many BIAB brewers recirculate with a pump.

 

[Strangelove]

Thanks for the insights. I looked for a floating dairy thermometer without much luck. What other kinds of thermometers do you all use?

 

[NordeastBrewer77]

Thanks for the insights. I looked for a floating dairy thermometer without much luck. What other kinds of thermometers do you all use?

just look up floating thermometer.

 

[gunner65]

Not a floating one but...

For the money these are hard to beat and Bobby is a great guy.

CDN Digital Thermometer

 

[RM-MN]

Yes you need to stir periodically. That is why many BIAB brewers recirculate with a pump.

No you don't need to stir. You have the grain mixed in the full volume of water for BIAB and all the grain particles are surrounded with water.

that's exactly how i do it too. if you don't stir, parts of that mash get way to warm

Once you have added the grain and have it stirred in the mash only gets cooler.

I have a small hole in the lid of my pot and stick a long stem thermometer in there just for monitoring my wort's temperature but with a few batches behind me I know that if I don't open the lid and have the pot wrapped with something that insulates it that the temperature will not change more than 2 or 3 degrees in an hour.

 

[NordeastBrewer77]

No you don't need to stir. You have the grain mixed in the full volume of water for BIAB and all the grain particles are surrounded with water.



Once you have added the grain and have it stirred in the mash only gets cooler.

I have a small hole in the lid of my pot and stick a long stem thermometer in there just for monitoring my wort's temperature but with a few batches behind me I know that if I don't open the lid and have the pot wrapped with something that insulates it that the temperature will not change more than 2 or 3 degrees in an hour.

i don't think thats right. have you ever taken temps at different depths of the mash? the temps stratify causing some grains to be too hot and some not warm enough. stirring keeps this from happening.

 

[jonmohno]

I have to stir,Ive seen spikes when i dont, sometimes temps will jump 10 deg. and im like ****. Then i stir and it goes back down. I dont think i ever actually know my actuall mash temp though, but i get an average and try to keep it there and i dont care if it raises some the last 20 min.

 

[NordeastBrewer77]

yeah, me too. i've seen the hot spots like 20+ degrees warmer than the cool spots. i.e. mashing at 152, hot spots are in the 160s and cools spots below 140. i stir, wait third seconds and the whole mash'll be 151. FWIW, my last brew netted me ~80% efficiency. took a FG reading today @ 15 days, .001 off my target and it tasted divine. :rockin:

 

[plumbob]

Yeah I definetly disagree, from my own observation the mash develops hot spots. Indeed the mash as a total only gets cooler after you take it off the heat, but it can have some spots that are 140F or 160F. Particularly, depending upon your method, the top of the mash can cool off a lot so to get good conversion on that top half inch of grain you have to stir.

 

[NordeastBrewer77]

Yeah I definetly disagree, from my own observation the mash develops hot spots. Indeed the mash as a total only gets cooler after you take it off the heat, but it can have some spots that are 140F or 160F. Particularly, depending upon your method, the top of the mash can cool off a lot so to get good conversion on that top half inch of grain you have to stir.

yep, that's what happens. the top, where all the heat escapes cools off, whereas the bottom, covered by hot grain, warms as the top cools. it's called stratification.

 

[Komodo]

Stir for sure. Also, I use a round cooler and lost a lot even with the lid on. Someone suggested making a foam disc, covered in aluminum tape that fits inside the cooler, as the heat is lost mostly IN THE HEADSPACE. When I used it, I lost 1-2 degrees in 75 minutes.

 

[Strangelove]

I wonder how the pros do it (micro or macro breweries). If I get hots spots and stratification in a 20"-tall pot, do they need to stir in a mash tun that looks like:

 

[djt17]

I do BIAB inside in the winter; I stir for the first 5 minutes to get the mash thoroughly mixed. Then wrap the kettle in an old sleeping bag & don't touch it for 60 minutes. 12 batches this way, no problems. In the summer when I brew outside & do traditional AG with my cooler mash tun, I also stir like crazy for about 5 minutes, close the lid, & don't touch it for 60 minutes. 14 batches this way, no problem.

 

[NordeastBrewer77]

I wonder how the pros do it (micro or macro breweries). If I get hots spots and stratification in a 20"-tall pot, do they need to stir in a mash tun that looks like:

yes, they do. there's usually a mixer in those things to keep the mash temp even.

 

[RM-MN]

i don't think thats right. have you ever taken temps at different depths of the mash? the temps stratify causing some grains to be too hot and some not warm enough. stirring keeps this from happening.

If you can make this happen on a commercial scale you have invented a perpetual motion machine. The too hot spots are because you had insufficient mixing when you mashed in. The temperature of the mash never goes up anywhere unless you add energy somehow, it only goes down. This is covered in your first quarter of thermodynamics.

 

[plumbob]

If you can make this happen on a commercial scale you have invented a perpetual motion machine. The too hot spots are because you had insufficient mixing when you mashed in. The temperature of the mash never goes up anywhere unless you add energy somehow, it only goes down. This is covered in your first quarter of thermodynamics.

This is true, I don't think anyone was arguing they could violate the Second Law of Thermodynamics. But, thanks for the academic snobbery. I have an engineering degree too, but I try not to wield it like a club.

 

[Strangelove]

The temperature of the mash never goes up anywhere unless you add energy somehow, it only goes down.

I agree if you are looking at the mash as a whole. The original point is that there are gradients in the mash. I did mix carefully: add 1-2 pounds, mix, repeat. Perhaps if the grain cant be mixed perfectly thermal conductivity comes into play:

 

[djt17]

I agree if you are looking at the mash as a whole. The original point is that there are gradients in the mash. I did mix carefully: add 1-2 pounds, mix, repeat. Perhaps if the grain cant be mixed perfectly thermal conductivity comes into play:

Stir until it feels like your arms are going to fall off, (at least 5 minutes), it will be mixed thoroughly.

 

[bighorn_brew]

I am 15 pounds into a BIAB 13.75 gallons of water, and definately, gotta stir HUGE temperature difference within the bag. My hope now is the bag holds up when I slowly pull the bag out.......I'll either be very relieved, or very....MFn PO...

 

[NordeastBrewer77]

If you can make this happen on a commercial scale you have invented a perpetual motion machine. The too hot spots are because you had insufficient mixing when you mashed in. The temperature of the mash never goes up anywhere unless you add energy somehow, it only goes down. This is covered in your first quarter of thermodynamics.

yeah, theory's great and all, but i'm talking the practical application in the BIAB mash tun. the temp stratifies, like it or not. i'm only a couple hours drive from you if you'd like to stop by one day for a demonstration of this happening in a mash.

This is true, I don't think anyone was arguing they could violate the Second Law of Thermodynamics. But, thanks for the academic snobbery. I have an engineering degree too, but I try not to wield it like a club.

right. i mean really, we're talking about simple facts here and talking big isn't going to prove those wrong.

I agree if you are looking at the mash as a whole. The original point is that there are gradients in the mash. I did mix carefully: add 1-2 pounds, mix, repeat. Perhaps if the grain cant be mixed perfectly thermal conductivity comes into play:

i think this is it. nothing heats up RM-MN, but the temperature fluctuates within the tun. that's why some spots are warm, and others cool and when you mix, it equalizes. don't need to be an engineer to figure that out.

 

[RM-MN]

i think this is it. nothing heats up RM-MN, but the temperature fluctuates within the tun. that's why some spots are warm, and others cool and when you mix, it equalizes. don't need to be an engineer to figure that out.

That's true, there will be different temperatures within the mash as it will lose heat through all sides as long as no additional heating is applied. My original statement said that it couldn't heat up not that there couldn't be parts that cooled faster than others. If you have mashed in and stirred until the entire mash and water are at the mash temperature there will never be a spot that gets too hot, only spots that get too cool.

 

[NordeastBrewer77]

can't argue with that. in fact, i know what you're saying is right, in theory, but this thread is about why to stir the mash, not the laws of thermodynamics and how they may or may not apply to brewing. a mash WILL inherently stratify, causing some spots to be too cool for proper conversion and some too warm for conversion, thus the need to stir. obviously we all know that the tun doesn't MAGICALLY heat up without a heat source, but like in any other body of liquid, the temperature stratifies.