Mash tun strike water temp question?

I finally made my mash tun today from a 50qt Coleman cooler and I must say that it is freaking sweet and works perfectly from a drainage/non-leakage standpoint! I'll try to post some pics on how I did it to help any beginners like myself.

I wanted to go ahead and test how it would hold temperature so I boiled up about 5 gallons of water and dumped it in there. I started the hour with a temp of 170 and after an hour it had dropped around 5 degrees to 165.

Again this was just water with no grains. Is a 5 degree drop over an hour good or bad with just water in there? I know a 0 or 1 degree drop is a whole lot better but I'm hoping you all will tell me that grains will thicken it up like oatmeal which should help hold the temps steady.

If you're temperature was equalized at 170 that seems like a bit too much of a drop. I find that if I stir my thermometer in the tun I get a better average temp reading. Different areas of the tun will be warmer than others. I observed exactly what you did until I started stiring my thermometer in the tun.

I also drilled several holes in my tun lid and filled it with expanding foam. That might help you out some too.

That amount of temp loss is fine. It will be less with grain in there. Your mash tun will be at a lower temp, which should lead to less loss too.

There are three heat loss activities that happen with a mash in a tun that doesn't have any heat correction.

First the cooler steals heat from the water as the walls and insulation heat up. This is about 5-6 degrees but obviously depends on the temp of the cooler.

Next, when you mix in the grain, the colder grain steals more heat. Again, hard to say for sure due to grain temps, but this is like 11F loss.

Last, over an hour mash, despite all the insulation, some heat makes it out into the air. Assuming you've accounted for the first two types of heat loss, this is like 1-2F over the hour.

StarCityBrewMaster said:

Again this was just water with no grains. Is a 5 degree drop over an hour good or bad with just water in there? I know a 0 or 1 degree drop is a whole lot better but I'm hoping you all will tell me that grains will thicken it up like oatmeal which should help hold the temps steady.

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Adding the grains makes a huge difference. I tested my 7 gallon cooler out with 2 gallons of plain water and it lost 10 degrees in an hour. When filled with 13 lbs of grains and a few gallons of water, it loses about 1 degree in an hour.

I'd say you're in fine shape.

Bobby are you saying there is a combination of all of those drops? I have seen where brewers add strike water that is 12 degrees over where they want to be for the hour knowing that it will drop that far. Your temps drops add up to around 20 degrees.


When I do my first mash - let's say I want the strike water to be 152 degrees for an hour. I start with water that's 164 degrees. Do I stir the grains around until the temp settles where I want it then shut the lid or is it a good idea to try and keep your temp a couple degrees higher for the loss over time?

If you want your mash to be 152 after all is said and done, you add the grain when the strike has cooled to about 163F. However, you can't go into a cold or even room temp cooler at 163. You have to go in at like 172 for room temp or 175 for cold coolers. You let the cooler suck the heat out for about 5 minutes and then stir the grain in after you get 163F on your thermometer.

Wait for a second opinion but this is reality.

Bobby_M said:

If you want your mash to be 152 after all is said and done, you add the grain when the strike has cooled to about 163F. However, you can't go into a cold or even room temp cooler at 163. You have to go in at like 172 for room temp or 175 for cold coolers. You let the cooler suck the heat out for about 5 minutes and then stir the grain in after you get 163F on your thermometer.

Wait for a second opinion but this is reality.

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Seconded

I lose about 10-12 degrees to the cooler and ~11+ to the grain (as Bobby said completely variable based on temp of cooler and grain).

So, if I want to mash at 155, I strike at about 178 and dough in at about 166.

ok that's awesome to hear so then my 5 degree loss was only to the cooler which is perfect considering I put it in at 170 and it dropped to 165 in an hours time. If I would have had grain to mash I could have "doughed" in at that temp and been sitting pretty!