Cedar Rapids Brewing Society

I've really been struggling with my mash temps and I'd appreciate some advice. I'm currently using a 5 gallon round cooler. My current process is to preheat the cooler with water about 10-15F higher than the target mash in temp. Then I let it sit while I crush grain etc. Next I open it up and stir it to cool it down to a few degrees warmer than mash in and add my grain. I continue to stir until I reach the sach rest temp, close it up, and bring it inside the house.

All is fine except I'm losing 4-6 degrees over the hour long mash. Should I be concerned about that? Should I try to add insulation to the cooler? If so what would you recommend? Should I just scrap it and try to find a better cooler? I've already tried filling the lid with foam. My batch sizes are only filling the cooler about 1/2 to 2/3 and that's at a mash thickness of 2qt/#.

carrisr wrote:I've really been struggling with my mash temps and I'd appreciate some advice. I'm currently using a 5 gallon round cooler. My current process is to preheat the cooler with water about 10-15F higher than the target mash in temp. Then I let it sit while I crush grain etc. Next I open it up and stir it to cool it down to a few degrees warmer than mash in and add my grain. I continue to stir until I reach the sach rest temp, close it up, and bring it inside the house.

All is fine except I'm losing 4-6 degrees over the hour long mash. Should I be concerned about that? Should I try to add insulation to the cooler? If so what would you recommend? Should I just scrap it and try to find a better cooler? I've already tried filling the lid with foam. My batch sizes are only filling the cooler about 1/2 to 2/3 and that's at a mash thickness of 2qt/#.

If you checked, you would probably find you have conversion in 30 minutes. So, take that into account. I think most mash tuns lose at least a couple degrees over an hour long mash. If you are converting, and getting the desired results, I would not worry about it. If you are really concerned about maintaining a mash temp for the full hour, there is always herms.

4-6 degree drop over an hour is pretty significant. Especially at room temps. I would guess that you need to get a better cooler or try wrapping it with a blanket. I get some drop in mine but just a degree or two at the most. I use an Igloo Cube cooler from Walmart.

I'm suprised your losing that much temp in a cooler. I only lose a couple degrees in a keg outside. I wrap it in a wool blanket, and I have a bigger mass ( no fat jokes ), but still I would think that the cooler would retain the heat better.
I usually figure 13-15 degrees heat loss adding my grain. Are you sure your starting temp is as high as you think? It could still be dropping slowly before you close the cooler. Maybe the cooler is still absorbing some of the heat.

My guess is that your initial temp isn't as high as you think. I.e., the temp hasn't equalized throughout the mash. I'd let it sit for 5 or 10 minutes and measure and see how close it is to what you initially had.

Or, if you're happy with your beer, keep doing what you're doing.

I second checking your initial temp after 5 minutes. It does take a few minutes for temps to even out across the grain bed.

FWIW, I think I lose 2-3 degrees over an hour. My mash tun is almost too big for 5 gallon batches with small grain bills.

What is it you're trying to influence with the mash temp that would cause you concern as a result of a 6 deg drop? If it's fermentability, I'd say you're looking at a 2nd or 3rd order effect that can be safely ignored. Check out Kai's white paper from his mash parameter study (http://braukaiser.com/wiki/index.php/Ef ... on_mashing). In particular, look at Figure 10. He only observed a couple percentage points of difference in the limit of attenuation for single infusion mash temps ranging from 144F (62C) to 156F (69C).

The relationship between attenuation (i.e. final gravity) and temperature is so ingrained as homebrewing gospel truth that one would expect it to be highly linear. That is, if raising mash temp by a few degrees really produced a meaningful change in the wort composition to enable a less fermentable beer, with a higher final gravity, then one would expect a linear relationship. However, that linear relationship isn't observed in Kai's data (or the Narziss data he references) until you're above 158F (70C). Regarding your example, let's say you started out at 156F and you ended up at 150F. According to the data in Figure 10, that means almost nothing.

I also suspect that most of us have significant (i.e. >5 deg) thermal gradients in our mash tuns and it's pointless to think that we're controlling the mash temp that precisely. Even HERMS or RIMS systems can only precisely control the temperature at the point of measurement.

If it is fermentability that you're concerned about, I recommend focusing on grist composition and mash duration more than temperature. I realize this flies in the face of advice given by pretty much every homebrewing expert out there (Palmer, Zainasheff, Strong, etc.), but I've never seen any of them actually present evidence of the mash temp/fermentability relationship over the temp ranges (144 - 158F) we typically use in single infusion mashes.

The DOCTOR is in the House!!!

I think JZ, Tasty, and Doc have commented that a few degrees seem to make little to no difference in the clone beers they have done. Kai is the only one I know of who does the testing to back up what he says though.
Kai's water testing made Palmer redo what he published in his books. I haven't looked at his mash temp data. I guess I should look at more of his work. Didn't he do a seminar at NHC last year?

I definitely think some further measuring is in order. I also agree that fermentability shouldn't be affected, but if you're targeting a nice dry finish and you start at 148 and end up at 142, I would think that you will end up with a different beer. I could absolutely be wrong though. I don't have to deal with that sort of drop in temp and if I'm low I'll add hot water to get me to where I need to be.

Long live Kai and our resident Doctor for preaching his gospel!

Thanks for the info guys. Yes, it's mainly the much ballyhoo'd control of mouth feel and dryness I'm concerned about.

I'll also try taking some more temp measurements to see if it's a distribution problem. The reason that I sort of ruled that out is that I'm usually 3-4 degrees high after I mash in, and I stir until it drops down to about a degree or so above the target. That usually takes 5-10 minutes of continuous stirring, so I was pretty certain that the temperature was as evenly distributed as it would get.

I think the small size of my mashes is part of the problem. they don't have nearly the mass that a five or 10 gallon batch. Less mass means less heat storage in general.

But maybe I should not worry about it that much.

Minimizing air space in the mash tun does seem to help.

My favorite mashtun I have ever used was Larry's 10 gallon polarware kettle. We rarely lost more than 1 degree with that thing even unwrapped. My keg on the other hand, loses heat pretty fast even with the wrap. I use my chiller as a HERMS coil to raise and maintain the mash temp. Like Lee said, you are only measuring one point of the mash. I use to use a floating thermometer to check multiple locations in the mash and found my current recirculation method seems to distribute the temperature well.