Measuring Mash Temps

I did another all grain this weekend and was getting different readings depending where I put my thermometer. On top of the liquid I get around 152 and deep in the mash I was only getting 143. Where do you take the readings at? Could this low temp have anything to do with me getting only 57% efficiency? I did a continuious sparge at 175 deg.

Yes it could have something to do with the poor efficiency.
I'd be concerened if I had more than a 1c difference.

You need to stir and mix the mash to get a consistant grain bed temp.

Brew-boy said:

I did another all grain this weekend and was getting different readings depending when I put my thermometer. On top of the liquid I get around 152 and deep in the mash I was only getting 143. Where do you take the readings at? Could this low temp have anything to do with me getting only 57% efficiency? I did a continuious sparge at 175 deg.

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What are you mashing in?
When I mash I will mix the strike water and grain and then stick my thermo in the mash and keep it there the whole time. I put the top on the cooler and let it sit for 5 minutes then check the temp. Once I hit 150 I let it sit for 20 minutes then check the temp again and stir everything up. I do this 3 times.

You dont want to over stir the mash but you dont want any hot-spots either.
I try to get a temp from the middle of the mash.

You really have to have a consistent temperature throughout the mash. This is the most critical step in all grain. Check it in several locations when you mash-in, stir until every place is at the correct temp. Add hot/cold water until it's right.

If you don't pre-heat your mash tun, I'm wondering if you'd get a significant amount of heat loss near the edges of the vessel (if you're not stirring more or less constantly). I've never fly sparged, so I don't know exactly how that would work.

I did pre-heat the tun and I am using a square Igloo. My strike water was at 170F.
I added some water at first, then grain then water then grain...etc untill I had all 12lbs in. I even added some boiling water and could not get an even temp reading. How long should I stir for?

Stir until the temperature is even. If the temperature is not even, you didn't stir enough. It isn't an "amount of time" thing.

what kind of thermometer?

I use a digital thermometer and heat my grain in a grain bag using an electric filament heater. It's not as great as the Igloo cooler things apparently but it is still ok.

Getting the temp right is critical. Watch over your grain religiously during the mashing process. Keep stirring it from time to time and probe the thermometer in different places to make sure you are getting an accurate reading.

Sounds like a cooler and leaving alone is a better option.