Beer Forum

Ever since I stepped up to 10 gallon brews I have been having trouble with hot spots in my mash tun. My mash tun is a rectangular cooler mash tun and to do a OG 1.070 beer I need all of the room in the mash tun. I have been measure varying temps from 155-165 with hotter temperatures at the bottom. I try to stir as best as possible to solve this situation but it seems to take at least 15 minutes for the temperature to equalize.

1) Will this dramatically increase the amount of non-fermentable sugars?

2) Any suggestions to eliminate these hot spots?

1) If you are stabilizing to the desired temperature, you should not have denatured too many enzymes to convert fulling in a 60 minute mash.

2) 10 minutes or so for the temperature to stabilize is not uncommon, especially in a mash tun with corners. You could try and mix the water and grain at the same time, that might help you get a more consistent mash, though I wouldn't worry too much about it. Just stir it up as best you can and let it stabilize for 10 minutes, then measure the temperature.

Good Luck!

Agreed, it does take a while for the temperatures to equalize. What are you using to stir the mash? I use a heavy duty wire whisk for my mash. Does a great job of breaking up clumps, much better than a paddle or spoon, and does a great job of equalizing the temperatures throughout the mash.

Love the whisk idea. You could try increasing your water/grist ratio and/or use some rice hulls as Gordon Strong suggests.

I just use a wooden spoon. I will try a whisk but what about hot-side aeration? Can't really up the water to grist ratio because I have no room left in the mash tun. Its hard to get a good stir cause the thing is too full. What would rice hulls do? I thought they were used to prevent stuck sparges? That is not a problem as I batch sparge.

Using some rice hulls is a trick that Gordon talks about in his book as a way to even out the temperature in the mash. It was a recommendation from Tasty McDole. I don't know the complete rationale, maybe someone could help out, but I imagine it helps space out the mash. I have experimented with them, and it seemed to help, but I don't have any side by side comparison. However, if you don't have any more room in your mash tun this won't help. Sounds like you need a bigger mash-tun. You could try replacing a portion of the grain with simple sugar. As far as hot side aeration, I think it runs really low on the list of concerns, much lower than getting the temperature even and breaking up dough-balls.

Sounds like you need a bigger mash-tun.

Yeah I most definitely need a bigger mash tun. It won't fit in the budget right now unfortunately.

You have to determine what the max. grain weight you can mash, having the grain covered with a couple of inches of water and still have the ability to stir it without having to mop the floor. It is a real number which you can't exceed or else your mash will resemble cooked rice with your shoes covered with mash. If you can't manage your mash consistency and temperature by stirring, you will have hot spots and clumps. It doesn't matter what you stir it with, you should be able to feel any clumps with your spoon, etc., if you brew often enough. I have even used the long green Blichmann brewing gloves to dive into the mash. Adding grain to strike water works better than the other way around. So you will need know your max. strike volume, too. If you recirculate, more water is a must.

Know your limits, and boost your gravity with DME or suitable sugar in the boil if you need more gravity.
Think less grain .....more water..... room to stir


Gary