Mash temp problem?

[John F]

I'm mashing an imperial russian stout at the moment, and my problem is that the thermometer reads 74C at the bottom of the (picnic cooler) mash tun, but a more acceptable 65C in the middle. I've been adding cold water to stabilise it but nothing seems to be happening. My thermometer is a plain glass 76mm immersion type. Am I having problems because it's (practically) fully immersed and therefore inaccurate? Or should I keep adding cold water?

[simple one]

Stir it to even out the temp. Then leave. 20 mins later, measure temp, alter. Repeat until done!

[John F]

Thanks, Simple One!
I actually realised this shortly after my post. I'm used to a much smaller grain bill, which evens out faster. The mash tun's practically full this time, so the heat takes longer to even out.

I'm making the Imperial Russian Stout from GW's European Beers book. I had some spare (600g pale and 160g crystal) malt so I threw them in too. Using the Wyeast Imperial blend to ferment. Looking forward to drinking it at Christmas (2012!)

[vacant]

That caught me out once. I wanted to increase the temperature so switched the element on. Nothing happened at the top but after a while I thought to put the probe at the bottom where I found a higher temp. Note to self: convection currents work in water, not in maris otter. DUH!

[edit1now]

That's why I went HERMS, that and wanting to do the stepped-temp mashes in Protz & Wheeler's BCEBAH.

[simple one]

Your welcome, we've all been there. I had a few dodgy mashes prior to getting things right.

A picnic cooler, a good stiring arm and reasonably frequent checks work for me. Not super precise, but within 1-2C.

[boingy]

It's amazing just how good an insulator grain can be. Stir that mash, baby!

[Invalid Stout]

I've only done a few AG batches but have noticed the temperature of the mash varying wildly. All my beer has ended up on the sweetish side so I imagine I'm actually mashing hotter than I think.

[adm]

I have found that using a paint mixer on a cordless electric drill gets me a much more consistent mash temperature than stirring with a big spoon. The helical design (and speed) seems to mix the mash much more efficiently and ensure a more even temperature throughout.

It's also easier!

There's a school of thought that says the shearing action of this approach might cause a more compact grain bed and stuck sparge - but i have not found this to be the case, although so far i have only ever batch sparged. It also seems to give me a few more points of efficiency that when I stir by hand.

Your mileage may vary wildly - and of course if you stir it around really, really well by hand, you'll get just as even a temperature, but I'd rather have it done inside a minute.