The laws of physics have been suspended in my mash kettle

[william_shakes_beer]

OK, let me start off by saying I am not a new brewer. I have been brewing for 7 years, all grain for 5. This has never happened to me before. Probably about 45-50 batches through my kettle. I am at a loss to explain, except to conclude there is a micro black hole in my mash kettle pumping heat in from a supernova in another galaxy for the express purpose of ruining MY wort. Probably something to do with the displeasure of Mr. Shakespeare. Here's the back story:

Brew in a bag, all grain Chocolate milk stout. 15 gallon brew kettle doing a 5 gallon batch. I drew 7.5 gallons of tap water, dropped in the empty grain bag and fired her up. After 35 minutes the trusty old Thermapen wired cooking thermometer tells me at 170F its time to drop the grain. Cut off the heat, dropped in the grains and give it a quick stir to ensure all the grains are " thoroughly acquainted" with the water. Cover and go inside for 10 minutes to collect hops, lighter, cutter and a glass of beer. I return to discover my trusty Thermapen tell me the mash is now 199F. Let me say that again. 199F. Panic mode ensues. Frantically stirring the pot trying to bring it down to mash temp before the enzymes give up the ghost. 189. Lift the bag and see water vapor rising from both the water and the grain. Hold that sucker right there, partner. Arms trembling cause I'm kinda a wuss when it comes to moving heavy objects. Finally get it back down below 175. Firm stir, cover and after 30 minutes its flirting with 155. Groan. I finally get some blood flowing to my brain and realize its most likely a bad temp sensor. Hmmm..... Get out the refractometer after 60 minutes and SG is right where it belongs. Sigh. Now about that sensor... test... by leaving in until the batch boils. At first roll, the sensor is dead nuts on at 212F. Now I'm confused again. Here's the questions:

1. For those of you that play with thermodynamics; is it possible for a kettle to rise in temp with no added heat merely because the grains formed an insulation barrier? Remember, I gave it a stir after dropping the grains. In past batches the temp has always DROPPED slightly after adding the grains, due to the colder grains gaining heat from the warmer water. That's why I cut off the heat at a temp so close to denature: to allow for the temp drop due to grains.

2. Is it possible for a temp sensor to fail and then unfail? Is it possible for it to show an accurate temp, then a wildly inaccurate temp, then an accurate one again in the space of 30 minutes? for those of you that have had a sensor probe fail, what's the usual symptom?

3. Anyone else with similar overtemp occurrences? Did you discover the root cause?

4. Does anyone know the duration of time needed above 175F to denature 50% of the enzymes? is it possible that I denatures a significant portion yet there were sufficient remaining to complete conversion?

 

[balrog]

What's different about your burner, that would be my first question. Doing things the same with a different result kinda means something is different. I cannot leave my BK on propane burner stand after cutting heat because the cast iron stand will continue to load the BK with more heat and I've not determined the amount, repeatably.

Denaturing enzymes time, with temp, is above my pay grade, so hopefully someone smarter can chime in.

But from a Physics standpoint, without adding heat, you can't increase temp.

 

[RPh_Guy]

After 35 minutes the trusty old Thermapen wired cooking thermometer tells me at 170F its time to drop the grain.

Stir the water before measuring the temperature?

 

[bleme]

I've had 3 digital temp sensors go bad so far. All of them would start reporting much higher temps off and on. Now I always use 2 separate sensors, usually a digital (so I can set alarms) and an analog (to keep me sane).

 

[jerbrew]

I agree with the above that something has to be different in order to obtain a different outcome. I'll answer to the best of my ability below:

1) You cannot increase the temperature without adding heat or doing work on the system. That would be magic, thermodynamics is not magic, that's electricity. My guess without being able to see what's going on or observe your process is stratification in water temperature. You might be surprised how stratified the temperature of 7.5 gallons in your kettle may be. Perhaps in this batch, for whatever reason, your hot liquor wasn't properly mixed? tough to say. All of the heat required to increase your temperature up to ~200F was already somewhere. You probably did measure 170F in that specific spot but the bottom may have been close to boiling. Adding your grains and mixing aided in heat transfer throughout the entire kettle, ending up in a higher bulk temperature.

2) Short answer is yes. However, I don't think that is what is happening especially since those thermapens are pretty rugged and your "error" temp makes too much sense to be an error.

3) I have experienced this in many applications not directly pertaining to brewing. However, I have seen some carry over in my old cooler mash tun. Preheat with hot water, add some cool water to get to strike temp, add grains, mix, rejoice in hitting strike temp, come back to find it 2 degrees higher. Not the end of the world but the cooler had enough heat "stored" from the preheating and my process happened quickly enough such that the cooler helped raise the temp slightly.

4) No idea, but I do believe that as the temperature increases the time taken to denature X% of enzymes is reduced exponentially, but I'm no biologist.

 

[william_shakes_beer]

Cast iron banjo burner. Hadn't thought about it providing heat, but you're probably right. I am resuming brewing after a hiatus, (2nd batch in 2 months)so I guess it is possible some of the burner jets got clogged with dust. altering the performance and increasing the heat it absorbs. Lesson 1, stir before adding grains. Thought I already did that, but not sure.

 

[mongoose33]

I used to do BIAB on a Blichmann Hellfire burner. It took me 2 or 3 times until I realized how much residual heat from the burner was making its way into the mash.

I learned to wait about 5 minutes before deciding what the temp was. Pic below showing how much the burner was heating up the support structures.

Now, in your case, presumably that's not different than before, and some good ideas above about what you might consider as the cause. But there's no doubt that the burner will continue to radiate heat into the kettle after flameout.

 

[william_shakes_beer]

As stated in the OP, when I lifted the grain bag I noted water vapor rising from both the water and the grain bag, further suggesting the sensor was not in error and I do indeed have a residual heat issue (or a black hole ) Who would have thought to stir a pot of hot water?

 

[passedpawn]

As stated in the OP, when I lifted the grain bag I noted water vapor rising from both the water and the grain bag, further suggesting the sensor was not in error and I do indeed have a residual heat issue (or a black hole ) Who would have thought to stir a pot of hot water?

Who? Every person with an electric system, for one. My HLT has an element in it. The surface can be near boiling, but the temperature sensor at the bottom reads 80 or 90F less than the top. I have to circulate the water with a pump. Same situation in my boil kettle.

 

[Yooper]

Who? Every person with an electric system, for one. My HLT has an element in it. The surface can be near boiling, but the temperature sensor at the bottom reads 80 or 90F less than the top. I have to circulate the water with a pump. Same situation in my boil kettle.

Yep, me too. I added a stirrer with a little motor to agitate the water in the HLT because that's exactly what happens.

Even in an aquarium where you have a little 15 w aquarium heater, the water has to move or you'll have the area around the heater warm and the water across the tank too cold.

Water is a poor conductor of heat, and needs to be stirred/mixed to maintain a temperature across all of it.

 

[Bobby_M]

1. Don't put your bag in until you reach your temperature. It was creating a thermal barrier where the water was blazing undereath and you measured from above. Stirring the grains in allowed it to finally mix.

2. 170 is way too hot. Rarely do I ever need to go higher than 158F.

 

[bracconiere]

My temp probe is slow...gotta stir the strike water...

but i just had to post to say, LOL. your post was better then netflix!

 

[mongoose33]

Yep, me too. I added a stirrer with a little motor to agitate the water in the HLT because that's exactly what happens.

I've got something similar. Mine is a stainless steel lever about 18" long with a sort of scoop thing at the end. It's held by five gripper things that connect it to the biological motor which propels it around the kettle in a clockwise pattern--though with a simple flip of the cognitive switch it can be made to move counter-clockwise.

The beauty of it is the controller can be reprogrammed almost instantly, allowing for anything from a 2-second stir up to 10 minutes.

 

[hottpeper13]

I'm not a partical physicist, but could it be that there is an identical mash kettle in another galaxy where their heating up when you already have the grain in yours and that is where the extra heat is coming from? Just thinking outside the box(kettle).

 

[Pkrd]

-though with a simple flip of the cognitive switch it can be made to move counter-clockwise.

The beauty of it is the controller can be reprogrammed almost instantly, allowing for anything from a 2-second stir up to 10 minutes.

My experience is these cognitive switches can be quite unreliable. They can often get lost in an uninterruptible loop watching football or playing video games while your water stratifies.

 

[balrog]

And then sneeze into the chilled wort

 

[Mer-man]

Bobby is probably onto something.

And I bet you’ll measure temp AFTER integrating your water and grain next time

 

[william_shakes_beer]

sure will.

 

[william_shakes_beer]

And no, I was not drinkin' at the time. It was 9am fer cryin out loud

 

[balrog]

I'm sorry. What does 9am have to do with the drinking beer question? It looks like english words but they making no sense at all.

 

[bracconiere]

And no, I was not drinkin' at the time. It was 9am fer cryin out loud

I'm sorry. What does 9am have to do with the drinking beer question? It looks like english words but they making no sense at all.

i'm confused also...i thought 9am was a standard time for breakfast? i've got both, cider, and beer on tap...so apples and cereal for me!