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Old 02-22-2013, 12:36 AM   #1
Sep 2012
Boston, MA
Posts: 106
Liked 2 Times on 2 Posts

Hey all,

I'm 6 AG batches in and I've made huge progress in my technique thanks mainly to HBT. I feel like I've got a pretty good hold on my AG process except for one recurring issue around mash temperature.

After struggling to hit my strike temps, I started preheating my strike water to about 5 degrees above strike temp, pouring into my 42 quart rectangular mash tun, and waiting till it dropped to strike temp to dough in. I also built a styrofoam insulator to minimize headspace. Both these moves helped me keep temps within a reasonable range but I'm still struggling.

On my last brew I waited till my water hit strike temps (also preheated my mash tun with about a gallon of boiling water) and then doughed in. I used to calculate temps and the mash tun was indoors. After quickly stirring everything up I tried to take the temp to get an idea if I had hit my mash temp. However, I experienced big temperature swings with my instant thermometer (like 130-160) and I think I left the mash tun open a bit too long as a result. I struggled to maintain temps throughout the mash and had to pour some hot sparge water in to keep the temperature above 148.

So I have a few questions I'm hoping the veterans can answer:

-Should I just have faith in the calculations and hold off on taking the temp until 30 minutes in? And just shut the cooler as soon as possible after stirring?

-Is there a better way to monitor temperature (without going crazy) than to try to get a quick reading while stirring occasionally? I have considered buying a long thermometer and sticking it through my styrofoam insulating layer so I can get a temp read without totally exposing the grain bed to cooler air..good idea?


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Old 02-22-2013, 04:01 AM   #2
Apr 2008
Cheektowaga, NY
Posts: 741
Liked 38 Times on 36 Posts

While digital thermometers are great, they can lead to the results you've listed above: trusting too much to the temp swings as it contacts hot or cool spots in the tun. To fix that problem either use an analog therm or do as you also suggest- wait a minute to take a reading. Personally I use an analog thermometer- because it's cheaper- and take many readings in various positions (both lateral and vertical/ depth) within the tun after dough-in.

To answer you questions:
1. Yes. In my experience the calc's are right. BeerSmith tells me to strike a cold tun at 164.5 for a 152 mash target, I do it. Only when I stray from that strike temp have I had a problem. Like so many other things in this hobby you must know your equipment. If the calc's you use always end up a degree low, be aware of it and adjust accordingly.

2. I'll again use my technique for example (because it's the only one I know...). While the thermo is in the mash, stir constantly but gently. The goal here is to evenly distribute both hot and cold spots. Check the temp in various locations and depths in the mash. I leave the thermo in the tun throughout the mash and check it 4 times: during the initial stir as described above, after leaving it set for 5-15 minutes, at the 30-45 minutes mark, and when the mash is finished.

What are your temp drops during the mash? As in, if you settle at 152, do you end at 152, or does the temp drop to 145? Those data won't help much with your strike temp problem but it may reveal any heat loss through the tun- especially since you preheat. Kyle

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Old 02-22-2013, 09:55 AM   #3
Nov 2010
Madison, WI
Posts: 180
Liked 17 Times on 14 Posts

I just ordered one of these, and plan to get a submersible petn probe for it so I can leave it in the mash tun (70 qt extreme cooler) and monitor long term temp losses without opening the lid. With a second probe I will be able to monitor shallow/deep, each end, whatever I want. It can also be calibrated by the user. The probes I saw cost more than the unit :-(, but petn is food safe, so of course it cost more....

Forgot the link

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