Mash Tun Size, & Stir or not to stir

[Chayes0724]

This may be a bit of a stupid question. But I am struggling a bit with mash tun temperature and have a feeling it may be the size of my mash tun. I bought a 10 gallon home depot cooler and converted it to a mash tun. However, im only doing 5 gallon batches at the moment. Which means my mash is about 3.5 gallons plus grains. Could this be the reason I am losing about 3-5 degrees during my mash, just too much empty space in my mash tun? Also, it always seems to me I hit my mash temperature until I stir my mash after an hour. The top of the mash seems to be perfect, then I notice a huge (5 degree) drop in temperature after I stir. Should I be stirring my mash or just sticking the temp probe all the way to the bottom of the mash tun. Thanks in advance!

 

[Rodent]

Q: do you pre-heat your cooler tun prior to mashing?

 

[Chayes0724]

Ive done it both ways. I am getting closer to the temp by preheating yes. Id say if I don't id lose about 5 degrees. If I do maybe 3.

 

[Rev2010]

10G coolers are the typical size for 5 gallon batches so nothing wrong there. You definitely need to preheat your mash tun. To preheat you will want to shoot for 15-20° higher than your desired rest temp. So if you want a 152° rest I would preheat the tun with 170° water and let it sit for at least 15 minutes, longer is even better. As for stirring, I have done 3 stirs over an hour mash, 2 stirs over an hour mash, and no stirs other than dough in for the hour and I've found its better to stir well on dough-in and not stir throughout the mash. I've had no difference at all in efficiency/conversion from doing just the one stir and the heat loss isn't worth it. Though, on the flip side most conversion happens in the first 15 minutes or so so I am not sure the heat loss is also that big a deal. Anyhow, I'd stay stir it up well at dough-in and leave it alone for the hour. If you do want to stir along the way only do it once halfway through the mash at most.


Rev.

 

[Chayes0724]

Ok great. I was seriously considering getting a 5 gallon cooler. I’ll just heat the tun up more next time and keep the hot water in until I’m ready to mash. Thanks a lot for the advice!

 

[RM-MN]

This may be a bit of a stupid question. But I am struggling a bit with mash tun temperature and have a feeling it may be the size of my mash tun. I bought a 10 gallon home depot cooler and converted it to a mash tun. However, im only doing 5 gallon batches at the moment. Which means my mash is about 3.5 gallons plus grains. Could this be the reason I am losing about 3-5 degrees during my mash, just too much empty space in my mash tun? Also, it always seems to me I hit my mash temperature until I stir my mash after an hour. The top of the mash seems to be perfect, then I notice a huge (5 degree) drop in temperature after I stir. Should I be stirring my mash or just sticking the temp probe all the way to the bottom of the mash tun. Thanks in advance!

Have you ever considered that you are looking at the wrong problem? Maybe it isn't the temperature drop from stirring after an hour. Maybe the problem is that your mash period is too long? Maybe it is the stirring? I only stir my mash to mix the grains in well or if I feel the need to take a hydrometer reading. Mash temperature only matters while conversion is going on. If conversion is over, temperature isn't critical. The time until conversion is complete is dependent on the quality of the crush which also is a big factor in mash efficiency. So now the question becomes, how long does it take for your grain to completely convert and then following that, how does a temperature drop of 5 degrees over an hour affect the fermentability of the wort? If your beers always turn out too dry (low FG) then the drop in temperature can be the cause. If they end up with the proper FG for the beer you are making, the temperature drop can be ignored or can be compensated by starting the mash at a higher temperature.

 

[Gilbert Spinning Horse]

I've seen people cut out a sheet of rigid plastic to the size of the mash tun and place that on top of the grains. Not tried it myself but the reports are that it helps retain the heat, which would make sense.

 

[McKnuckle]

^yes, and it is especially effective if you use a thick rigid foam insulation to make the disc. It's sometimes called a mash cap.

 

[bracconiere]

^yes, and it is especially effective if you use a thick rigid foam insulation to make the disc. It's sometimes called a mash cap.

Just keep in mind that wouldn't help with LODO (being that was the first time I ever heard of a mash cap myself)

 

[schematix]

temp stratification is a real thing. You must stir regularly.

2 things i can add:
1. You can do full volume / no sparge batches with that large of a cooler. Max gravity probably around 1.050-1.060 though. Makes brewing much less complicated for only a minor hit in efficiency, which isn't much for modest beers anyways.
2. Look into 120V RIMS and a pump. Recirculating mashes are great. You can do this on the cheap for batches this small. It'll maintain and slowly step temps if needed (although don't go too hot in a cooler as it'll warp the plastic). This will fix both the stratification AND temp drop issue.

 

[brewhaus88]

I use stir at dough-in, once in the middle of the process, and once at the end. You really want to mix in the grains to make sure you get out any clumps that have formed. I have moved to recircing for the mash time using a pump to avoid hot spots. This circulates the mash and creates a stable temperature throughout the mash tun. As for the temperature, do you have the lid off? I seen maybe a 1 or 2 in temp difference but never 5. You could try to wrapping the cooler in some reflectix insulation to keep the heat in.

 

[bracconiere]

you could also draw about a gallon or half of wort from the cooler, 15-20min in, bring it to a boil and add it back to it...i think people have made calcs for doing just that sorta thing...

 

[McKnuckle]

you could also draw about a gallon or half of wort from the cooler, 15-20min in, bring it to a boil and add it back to it...

The reason this is not a great idea is because you'll denature enzymes in that liquid when you boil it. Better to do a decoction, where you boil the solids rather than the liquid wort.

 

[bracconiere]

The reason this is not a great idea is because you'll denature enzymes in that liquid when you boil it. Better to do a decoction, where you boil the solids rather than the liquid wort.

i'd be worried about tannins then...and i don't have a problem with conversion, that's what i do for a separate beta/alpha rest....pull about 2-3 gals off of 7 starting....

edit: sounds like he's got room too, could just pull a bit of sparge water and bring it to a boil and add it also

 

[Rev2010]

i'd be worried about tannins then...

Yet German brewers have been decocting this way for centuries without a tannin problem. I've double decocted hefeweizen's also without any tannin issue.

Honestly, I think this is being made more complex than it needs to be. OP just needs to preheat his tun better, mash in and stir really well, make sure he's hit his initial desired temp, then seal it up and leave it alone.


Rev.

 

[bracconiere]

Yet German brewers have been decocting this way for centuries without a tannin problem. I've double decocted hefeweizen's also without any tannin issue.

Honestly, I think this is being made more complex than it needs to be. OP just needs to preheat his tun better, mash in and stir really well, make sure he's hit his initial desired temp, then seal it up and leave it alone.


Rev.

but complication is what we like here, right? we wouldn't want the 'average joe' thinking brewing was easy!

(but your probably right, it is easy! i hesitated to tell him, 3-5f don't make a difference over an hour)

 

[troypolla]

I preheat mine as well. I actually boil one gallon of water and put it in the MT with the lid on while I am heating the strike water. I dump it out just before I mash in. Usually the drop is 2 degrees in an hour.

 

[RM-MN]

i'd be worried about tannins then...and i don't have a problem with conversion, that's what i do for a separate beta/alpha rest....pull about 2-3 gals off of 7 starting....

Tannin extraction is driven by pH, not just temperature. Your mash should be well below the 6.0 pH threshold to extract tannins even if you boil the mash. Unless you are using a malt bill that is low in enzyme activity like lots of Munich, boiling a gallon of the wort at 20 minutes probably won't have much effect on the enzyme activity as there is usually an excess in the malts. Pale malt contains sufficient excess enzymes to convert the starches with a 60% unmalted grain bill.

 

[Wolfbayte]

Your cooler is not too big. Is the lid insulated? Of not you can use some spray foam to decrease heat loss through the lid.

Also, what is your wrap situation? I wrap my 42 qt cooler with a reflective sun shade and then a blanket, hold it tight with a bungee cord over the top, clamp the blanket closed in the front and back and only lose about 2° over the hour.

Grain thickness can help here too. I mash with at least 1.5 qts per lb of grain.

Opening the lid can cause heat loss especially this time of year. Try leaving it and stir again really good before lautering.

 

[Homergah]

I'll throw my .02 in. I've had what I thought was excessive heat loss when using the 10 gallon igloo water cooler. Fought it for some time. Turns out I wasn't properly stirring the mash at dough in, leaving cold spots. This would give me a false warm reading occasionally causing me to think I had hit my temp. The next time I would stir I would disperse the cooler mash throughout, lowering my overall temp more than I expected. A friend who is a pro brewer was over for a brew day and when I was doughing in he asks, "what the hell are you doing"?

"It's called doughing in you dh."

"You're taking too long, give me the paddle"

Then he proceeded to stir like a madman. I mentioned hot side aeration.

He swore a bit then laughed.
"You believe in unicorns too?"

Anyway, make sure you mix well at dough in.

 

[kh54s10]

Pre heat, stir well to get all the clumps broken, wrap the tun in blankets if it is cold where you are. Close it up and leave it alone. every time you open to stir the temp will drop more.

IMO 3-5 degrees in an hour is perfectly normal with a water cooler tun and nothing to worry about since the majority, if not all, conversion is done before temp drops much.

 

[Rodent]

@Chayes0724 - when your future budget permits, you may want to consider underletting as the means to fill your mash tun during mash-in.

In its simplest form, underletting is flowing your mash-in water into your grain-filled tun from the bottom up via the drain port.

I use a small wort pump to pull heated mash water from my HLT and slowly push it into the mash tun. This has been a life saver for my bad back, and has completely eliminated (so far) the occurrence of those pesky dough balls when mashing in.