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How do you measure your strike water temp

Northern Brewer General
#1

I vigorously stir my water every 5 minutes or so as its coming up to temp, on the assumption that its not naturally going to heat evenly and I need to continually mix it to get a uniform temp. It seems to work pretty well, although when stirred the center of the whirlpool tends to run a couple degrees hotter than the outsides. Am I wasting my time with this exercise? What do you do with your strike water?

Anyone know the physics of how water heats up? I’d assume it be hotter at the bottom because that’s where the heat source is, or maybe hot water rises like air does? Or does the hotter water transfer its heat to surrounding colder water, essentially helping everything heat more or less evenly? I have no idea, and now that I’ve been thinking about it I really want to know. Someone help me.

#2

You are better off not stirring the water at all.When you stir and make a whirpool you create concentrations of heat. That’s kind of what keeps the whirlpool going as the heat concentrates and pulls cooler water into the core. Just like a tornado does. If you don’t stir the natural convection will cause the hotter water to move to the top of the pot and the cooler water to naturally fall to the bottom. Convection is natural. It just works.

#3

I’m barely schooled in physics but I stir well. I believe it better equalizes the temperatures for a measurement.

#4

[quote=“pb905”]
I’d assume it be hotter at the bottom because that’s where the heat source is, or maybe hot water rises like air does? Or does the hotter water transfer its heat to surrounding colder water, essentially helping everything heat more or less evenly?[/quote]

All of the above + whirlpool effects
Fluid dynamics are complex :smiley:

#5

Very true. The geometry of the pot, the material of the pot, the volume/surface ratio of the water, the volume of the water, the area of the heat conducting surface (pot bottom), the power of the heat being supplied and if the pot is covered or not will all play a role.

If you want to make sure the water is as uniform as possible, then use a pot that is insulated around the outside, will be fairly full, heat it slowly, stir it gently in a random pattern (a figure eight works pretty well also) and keep the cover on. I’ll let you figure out how to do those last two things together.

Or you can just let it be. As long as the heating takes long enough, conduction aided by natural convection will get things even to the point where it will be difficult for you to tell the difference.

#6

i stir but not in a circular motion. I go from side to side, gently

#7

so for a country bumpkin BIAB’er, measuring strike water at the surface with a deadly accurate thermapen, what would you guys recommend? I seem to be hitting target mash temps pretty well, if not really well. Is my mash stratified too? Again, getting solid fermentable worts, but just curious. Good thread!

#8

I enjoy pondering about these sort of things but it can lead to paralysis by analysis. The easy answer is that the temperature of the strike is much less important than the resulting temperature of the mash. Despite what you read, I believe mash temperatures are more forgiving and less critical than popular belief. Personally, I think pH is the main variable and temperature secondary, but BOTH are a critical part of the enzymatic reaction along with other variables that affect the reaction to a much lesser degree (IE: water to grain ratio, crush, and mash duration).

To address the question directly, I only stir once the temperature nears my strike as I am milling my grain as the HLT is heating (lid on). I know from experience that if I don’t stir the temperature is less stable. Maybe I am the only one doing this but I stir and check final temp AFTER cutting the heat. I think my HLT (kettle) retains some heat.

So we have: fluid dynamics, convection, conduction, but what about water composition? Depending on the alkalinity and hardness of your water. . . :smiley:

#9

Yeah this seems like something that isn’t terribly important. I always heat my strike water a few degrees higher than it needs to be then stir it till it gets down to my desired mash temp. It’s much easier to cool your mash down than it is to heat it up especially if you are using a cooler mashtun.

#10

I heat up 25 gallons and don’t touch it. I usually end up not needing the last 5 gallons.

#11

Stratification is a common ‘problem’ with regard to temperature and pH, in home brewing.

Home brewers generally don’t have steam jacketed kettles, mash rakes and other devices which help to evenly distribute the heat and the mash.

It doesn’t seem to make a large difference though and is probably nothing to concern yourself with as you are stirring your mash after dough in and stirring your mash after adding sparge water (assuming you’re batch sparging). Not enough stirring would cause a problem, however.

If you are still concerned and want to measure the temperature at the bottom, middle and top of the strike water or mash, then I would suggest to get a NIST certified glass thermometer such that you can stick it down into the mash/strike water far enough. A NIST certified digital thermometer with probe extension would also suffice.

Beware that these device are expensive.

#12

Now: fluid dynamics, convection, conduction, water composition, NIST certification of thermometer, and… OK, I got one new one! Temperature compensation for elevation.

RDWHAH. Mashing and brewing in general is quite forgiving. Our forefathers did it without a thermometer and the beer was tasty and they got drunk. Life was good. Now, if some of this info is new to you, do yourself favor and get some thermometer basics. Many have reported homebrew thermometers off more than 10F…

Glass NIST $10
http://www.amazon.com/dp/B00551NIFI/ref=biss_dp_t_asn

Personally, I keep glass out of the brewing session but I do use glass to calibrate this:
http://www.amazon.com/dp/B00551NIFI/ref=biss_dp_t_asn
Unlike others, I calibrate to 150F. Mine is old, cracked, and bent but holds calibration well. This thread reminds me to check it again… :cheers:

#13

A BIG THIS. I never understood calibrating to freezing and boiling. When I start mashing at those temps I will calibrate at those temps.

#14

A BIG THIS. I never understood calibrating to freezing and boiling. When I start mashing at those temps I will calibrate at those temps.[/quote]
I can easily understand why people do that. It seems easy, and it’s intuitive. I isn’t until you understand some of the complexities of temperature measurement that you begin to realize that the simple answer doesn’t get you to where you thought it did.

#15

A BIG THIS. I never understood calibrating to freezing and boiling. When I start mashing at those temps I will calibrate at those temps.[/quote]
Well, one can boil water and check your thermometer at 212*, and have an ice water mixture to check at 32*. But what do you use to check at 150*? A calibrated thermometer? And how was that one calibrated? And on and on. Of course, most of us are not that terribly worried about it. If my mash temp. is 149 vs. 152, I’m OK with that. I just want to make sure I’m not 159 if I’m shooting for 149.
All the best! :cheers:

#16

I mash most of my beers around 150-152. I heat the strike water about 10 degrees hotter than that, 160. I heat my tun with the water and about midway, say 155,156 then I dump my grain. The temp settles out at the mash temp with some help from a sleeping bag or heavy blanket.

I don’t stir and sometimes I miss my temps by a few degrees but I always make good beer!

RDWAHAHB

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