Taking an accurate temp reading on MT?

So most of you will probably laugh but I'm sure there are some of you out there like me who hate these kinds of things. I'm taking about taking an accurate reading of my Mash temp. I ended up buying a nice digital waterproof thermometer with a long prob that I can stick in the mash. Its accurate, I'm very sure of that. Here's my frustration... just with common sense I can understand that liquids in a pot as they heat are going to be at different temperatures depending on where they are in the pot. I want to know what the average temperature is of my mash at all times. I hope I'm making my question clear. Basically my last brew session was very frustrating cause I had my new thermometer and things were going well. I doughed in and was a little warmer at around 157F so I stirred it a bit till it was around 152F and closed it up. I came back to check 15 min later and it was 148F. I pulled the prob turned it off and on and put it back in. Now I get 155F. So it seems like depending on where I place it in the mash I get different readings. Long term I'm wanting to build something like the electric home brewery but thats long term. I know I've seen guys that have systems that take temp readings and average it out between the different probes. Would you guys have any suggestions or am I just being to picky.

Matt

 

Depending on the thickness of your mash, you'll have a temperature differential, even with mash paddling, at different spots. The thermometer in your MT (if you have one) will read one temperature, and your stick thermometer will read something else on the other side (or even just several inches away). Don't worry about it too much. Get a good instant read (I'm a huge fan of thermoworks' products, such as the venerable thermapen), check a few places, stir any dough balls up (under the surface please!) The construction of your mash tun, the heat source (if any), and the mash thickness all play a part.

There are several schools of thought. Some people will take the average of 3 or so spots. Some people will use the hottest spot as the conversion temp. Other people will use the coldest spot. Remember that saccharification occurs at a range of temperatures; you don't need to hit it head-on.

 

A 5 gallon mash has 1155 cubic inches. Taking the temperature at any given point is only surveying 1/1155th of the mash. You would need 10 temperature points to even get close to surveying 1% of the mash.

So in terms of data validity, I don't really think you're getting any substantially "better" data from 10 probes than from 1 probe you can move around.

It's normal for the mash temp to vary a bit. How thick is your mash? Since water will heat more evenly, you could thin the mash out to get more uniform mash temperatures. I use about 5L/Kg, which is about 2.4qt/lbs.

 

I have the same issue. I'm wondering if the best solution is to keep the mash stirred and heat evenly distributed, rather than accepting thermal pockets and trying to get an average? I'm in a cooler so continuous stirring without bleeding heat all over the place will take some effort.

 

Well, this is why RIMS/HERMS systems exist. One of the homebrew clubs I've been a part of actually ran the exact same recipe. In a blind tasting, we universally preferred the infusion mash version. There is something to be said for saccharification occuring at a wider temperature range.

I wouldn't simply keep stirring - you're going to up your evaporation, lose heat, and possibly risk hot side aeration. I've seen automatic stirring devices which work below the mash level as well (eliminating HSA).

 

Yeah, continually opening/stirring is asking for heat loss and HSA. Also with you on the RIMS/HERMS helping (that part is in work for me right now). Although, it still seems that the temp distribution with a recirculating system is going to depend on how you return the wort to the grain bed and what your mash thickness is. Is the general thought to return through a piece of tubing on top of the grain bed with a thin enough mash to have a layer of liquid on top, making a little whirlpool? That should do the trick to distribute temp, right? Isn't that how the brew magic works as well? I tend to get lost in the weeds on some of these issues

 

I find there is a equalization that takes place after starting the mash. In other words, if you dough in and immediately take a temp its is going to be way different (and more variable depanding on where you are in the mash) than if you wait 5-10 minutes and then measure/adjust. This is even in a pre-heated mash-tun. If you don't pre-heat, the variability is going to be even more extreme.

I find that recipes can mislead someone into thinking that mash temps should be more tightly regulated than they really should/could be. For example, you see someone's recipe as having a mash temp of 153, but in reality what they have is a mash temp of 151-155. Sure they can get pretty close with recirculation, but is there really an observable (and desirable) effect with that level of complexity?

I usually consider recipes in 3 different mash temps and call it good. There is dry (148-151) normal (152-155) and malty (156-159). Anything more "fine control" than this gets too complicated to try and achieve.

 

Agreed!! x10. Alot of it has to do with preheating the mash tun and dispersion of the heat through the cold grains. You kind of need to trust your brewing software temps and verify after it has set for 5-10 mins. I have had times where it seemed too hot, you stir, then it gets too cold, then I am drawing wort and heating it to get back up to temp. I agree with the ranges for cooler mashing...you can get close to a target, but I'm not sure you can split hairs within a degree or two...at least I can't seem to with any confidence.

 

Awesome, thanks for the comments guys. The more I read what you were all saying the more it made sense. Without a system like a RIMS/HERMS that is monitored and heated with PIDs or some other sensor getting to a consistant single degree is always going to be difficult to verify. I use a Pot for my MT that I insulate with a jacket once its at temp. For my next brews I'm going to heat the water to strike level, dough in and do a temp reading after 10 min. I'm also going to take my readings from the center top of the mash and hope that if I'm in the same general area with all my readings it should be fairly consistant. It will probably be a few degrees cooler on the top than in the middle or even bottom. I also like the idea of viewing temperatures in the 3 categories that broadbill mentioned. I'll aim for those for the next one.