Help! Mash tun drops 10 degrees!

[TheOrlandoGuy]

So - I've used my little partial mash tun for at least 15+ brews at this point, and only recently have I noticed such a variation in my temperatures. It's gotten to the point where I cannot hold on to a constant temp without it dropping at least 5-10 degrees.

Some background info - It is a very small, 6 quart rectangular cooler with a spigot. I fill it with faucet water as hot as it can get (100+ degrees) and let it sit for about 15 mins to condition it before I mash. I can mash about 2.5 - 3 lbs of grain with about 5 quarts of water. I strike at 165F and can usually hit my mash temp dead on. After about 10 minutes, it has already dropped at least 3-4 degrees, and by the end of the full hour, I'm down 10 degrees from where I started at! It has always dropped some amount, about 5 degrees a year ago, but I feel like it has just been getting "worse" if that's even possible.

I keep my thermometer probe inside, with a wire coming out of the top to connect to my gauge- and something heavy on the lid to keep the weight on it. I can provide pics if necessary, but has anyone had this issue before? It's getting pretty frustrating.

Thanks

 

[LandoLincoln]

Well...in my own experience, mind you...

I hate probe thermometers. Hate them, hate them, hate them. They're unreliable and they fail. A lot. I've wasted so much money on them in my early days of brewing. My advice to you is to stop using them and get a decent stick thermometer. Brewhardware.com sells a good one that's only $17 that I have used for a couple of years now and it's never let me down, even after I've dropped it into boiling wort. Take a measurement before you close the lid, close the lid and just leave it alone for the full mash. Cracking the lid leads to heat loss.

The probe wire coming out of the top may be causing you to keep the lid cracked and letting hot air out.

A cheap and easy possible solution may be for you to lay a piece of aluminum foil over the top of the grain bed before you close it up. That thin layer of aluminum really does help to trap the heat in the grain.

Another possible solution is to get a piece of rigid foam to use to help fill up the dead air space in between your mash and the top of the cooler. Wrap it with aluminum foil and away you go.

If you try all of that and you still have significant heat losses (highly doubtful, but possible) then it's time to investigate how poorly the cooler is insulated.

 

[TheOrlandoGuy]

Thank you for the advice! It is time I finally do something about it instead of moping around when I look at my temp gauge - I will try the aluminum foil technique and ditch the probe next time. If that doesn't work, I may look into a new mash tun...

 

[hopjunkie26]

Yeah, I went through a number of probe thermometers but have since moved on. I have a thermometer similar to what Lando posted but I also built a thermowell to take temps with without opening the lid.

The only other thing you can do, other than Lando's advice, is cover the cooler with a blanket, such as a welding blanket, or get some insulation that can be added to the outside of the cooler. That could help with your loss of temp.

 

[aidan]

Some background info - It is a very small, 6 quart rectangular cooler with a spigot.

Since it's small and you have a small mash volume it won't hold the heat as well as a larger mass would. Mashing in a warm oven is one possible solution for small mashes.

 

[chickypad]

Since it's small and you have a small mash volume it won't hold the heat as well as a larger mass would. Mashing in a warm oven is one possible solution for small mashes.

+1. I mash all my 3 gal batches in a kettle in the oven. Preheat to lowest setting (on my oven is 170*), turn off the oven while mashing in, then put the kettle in. Zero temp loss over 45-60 min.

 

[EJay]

That exactly what I do too - I BIAB in a 5 gal kettle and put the whole shebang in a preheated oven.

 

[TheOrlandoGuy]

I've got to say....maybe it's becuase I've haven't dug deep enough on HBT, but I've never heard of a BIAB in an oven. I'm very intrigued now...

When you preheat the oven to 170, are you also heating up the mash water on the stove top to striking temp? Then add in the grains, stir, place in oven, and turn off heat?

 

[trussell]

x whatever on those probe dial thermometers. They look cool on a MT but I started using a floating thermometer and a digital therm. I found while the dial showed a temp drop the others did not. Stir and the dial would get close to true but then drop again while the others were more steady.

 

[chickypad]

I've got to say....maybe it's becuase I've haven't dug deep enough on HBT, but I've never heard of a BIAB in an oven. I'm very intrigued now...

When you preheat the oven to 170, are you also heating up the mash water on the stove top to striking temp? Then add in the grains, stir, place in oven, and turn off heat?

I preheat while the water is heating then turn the oven off as I'm getting ready to add the grains. I stir for a few minutes to hit uniform target temp, put the lid on, and place it in the oven.

 

[kombat]

When you preheat the oven to 170, are you also heating up the mash water on the stove top to striking temp?

It depends on how long your oven takes to get up to (the admittedly low) temperature. You know your equipment better than we could. The bottom line is that once you've hit your target mash temperature on your stovetop, your oven should already be at 170° F.

Then add in the grains, stir, place in oven, and turn off heat?

Yup, that's exactly what I do. Once my mash is at the precise temperature, the lid goes on, the pot goes in the oven, and the oven gets turned off. The mash should hold the exact same temperature for the full hour.

 

[TheOrlandoGuy]

You guys rock - thanks for enlightening me on this technique! I'm trying this on my next brew!

 

[helibrewer]

Since it's small and you have a small mash volume it won't hold the heat as well as a larger mass would. Mashing in a warm oven is one possible solution for small mashes.

Works great, that's the way I did my steeping grains back in my extract days too.

 

[guitarguy6]

I hate probe thermometers. Hate them, hate them, hate them. They're unreliable and they fail. A lot. I've wasted so much money on them in my early days of brewing. My advice to you is to stop using them and get a decent stick thermometer.

What thermometers did you try. I'm curios as I was about to pull the trigger on an MTC Thermocouple with the 113-372/373/375-T probe.

As for OP, I'd try wrapping the cooler in a blanket, covering the grain with aluminum and as others have mentioned using your oven and a pot. sticking the pot in the oven and checking oven temp every 15min or so has worked great for me in the past.

 

[TexasWine]

I've got to say....maybe it's becuase I've haven't dug deep enough on HBT, but I've never heard of a BIAB in an oven. I'm very intrigued now...

When you preheat the oven to 170, are you also heating up the mash water on the stove top to striking temp? Then add in the grains, stir, place in oven, and turn off heat?

I know I'm late to party on this thread, but I actually put my kettle in the oven the night before, put it on the warm setting at around 160F, go to bed and wake up the next morning with my water heated up and I'm ready to dough in.

And I also mash in the oven as others have described here.

If you're oven doesn't get down to 160 you could still heat a large majority of your water using this method and just reserve a little on the side at room temp so you can add it to knock the temp down to where you need it. Personally I think it's easier and quicker to bring the temp down this way rather than heating it up.

 

[madscientist451]

After reading texas wine's post about putting the kettle in the night before, I checked my range and its got a delay start function for the oven I always wondered what its for.
I can put a pot of water in there when I leave for work and be ready for brewing when I get home. Thanks to Texas Wine

 

[TexasWine]

After reading texas wine's post about putting the kettle in the night before, I checked my range and its got a delay start function for the oven I always wondered what its for.
I can put a pot of water in there when I leave for work and be ready for brewing when I get home. Thanks to Texas Wine

Hey, you're welcome! Glad someone found my rambling useful. I think that delayed timer was specifically put there for brewing.

 

[Peruvian802]

Good info on this thread. I've been meaning to put a dial therm. On my kettle for BIAB but given the fluctuations, it's probably not worth it.

I'm planning more 3 gallon stove top BIAB this winter and just figured out my oven goes down to mashing temps. Brilliant!

 

[TheOrlandoGuy]

Hey everyone, just wanted to says thanks again for the great info. Since my last post, I've used both methods of wrapping my mini mash tun in a blanket, and the BIAB in the oven. Both have given me great results (less than 3 degree drops), but I've gotta say, I'm hooked on the simplicity and minimal cleanup of the oven method!