Mash temp control problems...

A lot of all grain brewers utilize Rubbermaid Coolers as a mash tun to maintain consistent mashing temperatures.

http://www.northernbrewer.com/shop/brewing/brewing-equipment/all-grain-equipment/rubbermaid-10-gal-cooler.html

Cheers!

 

I built and insulating layer that fits over my kettle using stuff at Home Depot. Drops maybe a degree over an hour. You might try using a thick blanket to wrap over your mash tun while it sits.

Regarding hot and cold spots in the mash, you'll have some temperature variance throughout your grain bed, but it shouldn't be that much (maybe +/- 1 degree). Get a good thermometer or calibrate yours (Thermapens are amazing for this) to ensure its not your thermometer. It sounds like you mixed pretty well; I recirculate with a pump while heating my mash and while mashing in, until the temp stabilizes. Might want to vorlauf a couple times to ensure you're getting good mixing (on top of stirring). The fuller your tun, the better the temperature insulation.

If you already have a stainless mash tun, no need to go back to a cooler, although for very small beers, your 5 gallon cooler might be the better vessel to mash in (more full, less headspace, less heat loss than metal).

 

My cooler mash tun cost around $50 to build and loses less than 1 degree per hour. It is difficult and frustrating to try and maintain a temperature using burners, I'd just invest in a better insulated cooler.

 

Since I built mine according to this website, it's performed quite well. I use strike water that's hotter than my desired mash temperature according to brewsmith, and after three batches I've just about got my system dialed in perfectly. It equilibrates to the right temperature almost immediately. Last time I was only off by a degree, and even the first time I wasn't off by more than 3 degrees. The heat doesn't escape at all and my mash temp has been very consistent. I stir it four times during the mash, with no temperature issues.

Mind you I am doing 3.5-4.0 gallon batches, so my mashes are a bit smaller, and I'm only using a five gallon mash tun, not a ten. But it's worked quite well. This water cooler seems to really keep the temps well.

 

Stir alot at mash in, then cover mash tun and wait about 10min for temps to stabilize, then stir again, check temp. My guess is when you check it at the 30min in mark you didn't stir or stir enough, then when you added heat it overshot. Also try and insulate your kettle to prevent heat loss. The more you brew the more you'll learn your equipment, also be careful of the propane burner when adding heat during the mash, stir alot because it will heat up quick.

 

Will your kettle fit in your oven? If so, Preheat your oven to 200, cut the heat, hit your mash temp and throw your kettle in there. I don't think this will push your mash temp up significantly.

 

I would suggest doing a thinner mash; with a bitter like that, you could just go no sparge. Anyway, with a thinner mash, you'll use more water (say, 4 gallons if it will fit), and you won't need as large of a temperature differential to hit your desired mash temp (158 or something instead of 165). The grain will be much easier to stir, and you'll get the temperature to equilibrate throughout the system more quickly and reliably. I've been there, done that on the heating the mash tun, and it's not so effective (for me).

Also, you can re-circulate the wort to help even out the temperature, and supposedly rice hulls will help with evening out the temperature as well, by improving flow and heat transfer if you recirculate the wort. (Note: you really need to recirculate the wort if you start to heat the mash tun, otherwise you will start boiling the wort under the mash screen.)

 

I use a 10 gal Rubbermaid cooler with a false bottom. I recently did a nine hour mash of ~20lbs of grain. I laid a few pot holders on the otherwise uninsulated lid. Temp dropped from 154 to 148 over nine hours (damn, that was a dry Cream Ale!)

 

I suspect conversion was complete by about 8 or 8-1/2 hours. Probably 8.

 

20 minutes seems to be a consensus. I think it spent the next 8+ hours breaking down into simpler sugars as the temp dropped. I'll definitely do it again. Maybe not for a full nine hours, but for more than a couple. it seems like a good technique to perhaps mitigate a temp control problem.

 

HOLY SHIT..nine hour mash!!..wow..I think vikeman is right..8'll do it

 

If you calculated the mash in correctly, it takes a few minutes for temperatrure to stabilize throughout the mash. Stir it well, but then give it a couple minutes! Don't go off and add heat too early.

The best thing you can do for your setup is adding a pump to recirculate the mash. You can actually reculate the whole time if you want - I usually do. Take measure of the temperature of the wort that you are recirculating. You can add bursts of heat if you uneed to. If you do turn on the heat, keep in mind that the liquid that is recirculating is the stuff that just received the fire. It gets hotter quick. It's actually better to make yourself an electric RIMS tube (very easy and cheap). I can build them for about $20 not including temperature probe and QDs. Then you take the reading after the RIMS tube with a PID controller. You can let that controller run and it will keep your mash where you want it.

 

Also, I'm sure someone mentioned already, but "tin" foil is not a good insulator. In fact aluminum is a conductor and probably acts more as a heat sink that an insulator. The aluminum Bubble foil stuff is excellent however.

 

Remember that for the most part heat rises. Most tuns loose heat through the lid. This is because 90% of all coolers on the market don't have insulated lids.
They are just molded plastic with an air layer in there. In the OP's case he covered it with just foil! Which is a conductor of heat to boot. I suspect that was the largest culprit for the large temp drop. (But down to 146F isn't the end of the world in 75min.)

If you are going to use a pot to mash in, use a real pot lid and then cover it with a couple old towels or a folded up blanket. It will still radiate heat out the sides though so this isn't a complete cure-all.

When I used to mash in a 60qt cube cooler I would cover the whole lid with three or four ratty old towels I keep just for brewing. That seemed to do the trick.

I use a direct fired mash tun now where the top is largely open all the time. As I loose heat I just add some more. Recently, I started covering the tun with those same old towels and I find I am not cycling on the heat as often as I I did with out.

Moral of the story is to insulate your lids regardless of configuration. It will solve most of your problems with temp stability.

 

Totally agree here. I am mashing in a stainless steal pot and cover that sucker up with three towels, Two on the sides and one folded over several times on the top (using a real lid here.) I lose about 2-3 degrees over an hour with this technique. Since I am mashing on top of my stove I also leave the pot on the burner (turned off once I hit my strike temp), the still warm burner helps to maintain the temp as well.

 

I agree that the simplest route is good insulation. Another variation on this theme: I mash in a 7 gallon SS pot. I use a total of about 12 full sized bath towels to insulate, two below the pot (folded up) and 10 or so around the sides and top. For an hour mash I get a drop in temperature of about 2 to 3 F. Perfectly acceptable. It is important to get everything well mixed at the beginning. A thinner mash makes this easier; I like to use about 1.5 qt / lb.

 

I simply use my pump and direct heat to contain my exact temp on my mash. Works everytime

 

I know this is an old post, but lots of people are asking this question all around and this response comes up in search results. And I just want to clarify something: to stay at a mash temperature of ~155 you will want to preheat the oven to around 135. If you preheat your oven to 200, that heating element is going to get real hot, and when you put the kettle in there with the bottom right next to the heating element, your mash temperature is going to shoot way up.

You want to heat it to around 135, so the temperature differential between the pot and the oven is low: you're still losing heat but slowly. The smaller the difference between the pot temperature and the ambient temperature, the slower you will lose temp. (I feel like I'm back in Calculus class working with Newton's laws of cooling).