cooler/mash tun not holding temp

i tried my hand at all grain for first time today. i had my grain all mixed around and happy in my cooler the temp was 154.6f, being my all grain my goal was 152-155. i popped lid on cooler and set timer for an hr. after an hr first thing i did was check mash temp and it was at 148.8f. should i get it back up to 152-155 and let mash sit for 30 more mins? or should it be alright? thanks in advance

Did you preheat your tun? Also, did you stir the mash prior to taking the temp? The temp will be different in different places throughout the mash.

1. What kind of mash tun?
2. Temps vary based on where you insert your thermometer.
3. Did you mix very well?

Yup more questions... What kind of cooler are you using? have you filled the lid with foam? Do you wrap the cooler in a blanket? Just to put it into perspective, I have a 5 gal round rubbermaid cooler. I do not use the lid... I have a round of styrafoam about 1 inch thick wrapped in plastic that I use in its place. I have one of those car windshield insulators that I wrap around the cooler... And I still wrap that with a blanket. After preheating the tun, temp is rock solid after I mash in.

Oh yea I forgot to answer your question... It wouldn't hurt to add some boiling water maybe a cup at a time, stir and check temps till you get back to where you want it.

tun was preheated, i put in 2 cups of 170f water and sloshed around for a min and dumped out right before adding strike water. took first temp post 60min mash w/o stirring then took temp after stirring and the temp after stirring was 148.6f .2 degrees lower.

edwarski said:

tun was preheated, i put in 2 cups of 170f water and sloshed around for a min and dumped out right before adding strike water. took first temp post 60min mash w/o stirring then took temp after stirring and the temp after stirring was 148.6f .2 degrees lower.

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I am not sure if 2 cups of 170f water is enough to preheat a large mash tun. What type of mash tun do you have?

yeah i just have a home depot cooler and used that lid. i mixed strike water and grains thoroughly before closing lid and temp was at 154.6

edwarski said:

yeah i just have a home depot cooler and used that lid. i mixed strike water and grains thoroughly before closing lid and temp was at 154.6

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Ok. I use that one too. The big orange one?

I'd say next time preheat with more water and hotter water. Also be wary of temperature variations in different spots.

yep the big orange one. i added 168f water till mash came back up to 153.2f and im gonna let it sit another half hour.

edwarski said:

yep the big orange one. i added 168f water till mash came back up to 153.2f and im gonna let it sit another half hour.

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If you've already mashed for an hour and the least you saw was 148...you're fine...no need to do that...get to sparging!!

edwarski said:

tun was preheated, i put in 2 cups of 170f water and sloshed around for a min and dumped out right before adding strike water. took first temp post 60min mash w/o stirring then took temp after stirring and the temp after stirring was 148.6f .2 degrees lower.

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2 cups of hot water is not anywhere near enough to preheat. You MIGHT have just barely warmed up the skin of the plastic liner. Think of it this way. You cooler prolly has a temp of 68*-70*. When you preheat you want to raise the temp of the cooler to as close to your mash temp as possible, this involves raising the temp of the plastic as well as the insulation/foam of the cooler. When I preheat my 10 gallon cooler I put damn near 10 gallons of 190* water in for 10-15 minutes before I dough-in. This ensures that I have completely heated all of the cooler, even though I may only be mashing in with 4-5 gallons of water. The headspace (empty space above the mash) as well as the sides of the cooler that are not coming into contact with the mash will all suck heat from the mash. If you can heat those up before dough-in you will significantly cut down on temp loss. Also, stir your mash every 20-30 min to help keep the temp even across the grain. I found that the side of my cooler that the ball valve is on was often times cooler than the other side because the brass acts like a heat sink. I would imagine that your temp loss was from not preheating your tun enough.

Thats weird I never preheat, are you brewing in Alaska. Next time cover the lid with a blanket or jacket. I lose 1 degree F over an hour with the same cooler. I wouldn't say its a bad thing to mash out at 148F, the beer just might come out a little drier than you were hoping for. My only guess is that you did not stir enough and still had pockets of colder grain.