Inconsistent mash temp in rectangular cooler

I've done a handful of AG brews so far but I'm still definitely a noob. My biggest problem is that I can't get a consistent mash temperature in my rectangular cooler. In other words, when I stick the thermometer in one spot it might read 158, and in another spot it's 145. Mixing helps a little, but it seems there are always hot spots and cold spots. Is this normal?

All the books say that you need to hit your sacc rest temperature to determine the fermentability of the mash, 145-150 will generally be a dryer beer than 150-155. Ok, that's great, but how will my beer turn out if my mash tun is reading anywhere from 140-160, depending on where I measure? And if I'm going for a maltier batch and I want to hit 155, but parts of my mash are measuring 165, then I start freaking out and putting cold water in because I don't want to denature any enzymes.

I usually let the cooler soak in hot water from the tap before I start the mash, which is at about 135 out of the faucet (and if I'm doing a protein rest, then 135 is about the temp of the first infusion water). The cooler is very well insulated so I'm not losing a lot of temperature, I just have too much variation.

Is there any way to minimize this, or should I just take a handful of measurements and average them out to see where I'm at?

My process is to check the temperature in several areas, and if they are different, to stir some more! My gut feeling is that if you have areas of different temps, then perhaps the mash wasn't stirred well enough to equalize the temperature.

Agreed. You are probably not stirring enough. Don't just stir, dig your paddle down to the bottom and lift mash from there to incorporate the mixture vertically as well as horizontally. You will never achieve 100% temperature uniformity but a 13F differential is not normal. A couple of degrees is fine.

Ok, that's what I figured. I'll concentrate on stirring more fully this time.

How long does it normally take for the temperature to equalize (i.e. for the grains to heat up to water temperature)? A minute or two, or 10-15 minutes?

snottywong said:

Ok, that's what I figured. I'll concentrate on stirring more fully this time.

How long does it normally take for the temperature to equalize (i.e. for the grains to heat up to water temperature)? A minute or two, or 10-15 minutes?

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As someone more, um, eloquent than me said in a recent post about mashing in: "Stir like it's your god damn job!"

Even after thorough stirring, it can take more than 5 minutes to equalize. Stir, stir, stir, stir. Take a breath and stir, stir, stir, stir. Check for doughballs, and yep, you guessed it- stir, stir, stir. THEN check the temp in two- three places. If they are different, stir, stir, stir. Finally, check again throughout. And if they are different, stir again. It's probably harder than in my round cooler, but even in my round cooler, there is a big temperature differential if I don't stir enough.

Once you've stirred that well, and have temps equalized throughout, no need to stir again. You can just cover the MLT and walk away.

snottywong said:

How long does it normally take for the temperature to equalize (i.e. for the grains to heat up to water temperature)? A minute or two, or 10-15 minutes?

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You should stir for more than a minute or two. I stir for however long it takes to smoke a slow burning Pall Mall 100. Then I check the temp 10 minutes after that, so it has been about 15 minutes. I use my oven timer as a reminder then reset it for 45 more minutes.

Awesome, thanks for the advice everyone. I will get myself a pack of Pall Mall's. :rockin:

Sometimes I am in a rush and it's a real challange to me, but I find when I take the time to preheat my rectangular mash tun for a good half hour, get to my strike temp, and THEN dough in, I get much more consistent mash temps.

Stirring helps too .

Alan

snottywong said:

Awesome, thanks for the advice everyone. I will get myself a pack of Pall Mall's. :rockin:

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Make sure their 100's or you'll have to smoke 1.37 of them, or you could go with: 1.93 Lucky strikes, 1.6 Marlboros, 1.1 Marlboro 100's, or 0.72 American Spirits.

DrJerryrigger said:

Make sure their 100's or you'll have to smoke 1.37 of them, or you could go with: 1.93 Lucky strikes, 1.6 Marlboros, 1.1 Marlboro 100's, or 0.72 American Spirits.

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Or you could just buy a small kitchen timer and live a few years longer. LOL

C-Rider said:

Or you could just buy a small kitchen timer and live a few years longer. LOL

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But you would still need at least 1 Pall Mall 100 (or one of the listed substitutes) to time and see how long it takes to smoke one. Then you should smoke 10-15 more to be sure you have an accurate estimate of the time needed for stirring. It's science

C-Rider said:

Or you could just buy a small kitchen timer and live a few years longer. LOL

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A timer will not work the same. The cigarette burns at a different rate depending on how hard you stir.
And sure you live longer, but think about how cool you look .

DrJerryrigger said:

A timer will not work the same. The cigarette burns at a different rate depending on how hard you stir.
And sure you live longer, but think about how cool you look .

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Excellent riposte.