Partial Mash

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I'm currently doing my first partial mash and am wondering on the best way to keep the water at a constant 68C for steeping the grains.

I thought about an esky, but wouldn't it cool over 2 hours? At the moment I have a thermometer in a large pot with the grains on the gas stovetop, and am checking every 10 minutes. If it is getting down just under 68, I am giving it a short hit with the burner which brings it up to around 72 before switching off.

Any suggestions?

duff ,
I found having the griller on underneath on low keeps it at around 66 on my stove.
duff, it's surprising just how good the old esky is. I am using a very old one, probably about 15 years old (so it's insulation has probably deteriorated somewhat), and it still holds good temperature for over an hour. I start with water at about 74C. The minute i add it to the esky, the overall mash temp is about 71C. With the lid then closed for an hour, i have a thermometer positioned inside with external readout, and after 1 hour and 15 min, mash temp is 67-68C. You can also throw some towels or a blanket over the esky if you are concerned about the lid sealing properly. Anyway, i find it easier than keeping it on the stove, as there is a great variation between top and bottom of your vessel.
Hi Duff,
I used to do what Wardy said but I used to pre heat the mash tun with boiling water from the kettle and have the strike water at 71 deg c and would hit 67 every time. I just used to wrap a blanket around it for the mash time and it would hold temp no worries.
Good luck.
I mashed in a ss pot that would just fit in the oven. Having the oven on and set to 70 degrees used to hold the temp perfectly.
If you use an esky and there is a significant airspace above the mash, putting a sheet of aluminium foil on top of the mash helps to prevent heat loss too.
I use a 10 litre esky. Strike temp of 73C gives me a mash temp of 66C. I pre-prime the esky and manifold by filling with boiling water, which I empty and refil with the required amunt and temp of strike water. After dough-in, I wrap the esky in towels and a blanket and lose no more than about 1 during a one hour mash.
My bucket in bucket set up loses only a degree or two over a one hour mash. Just heat it up before adding the strike water. Then wrap everything up in a blanket with a belt around it.
Take note of these strike temps bandied around here, and keep in mind that they differ greatly due to the different water/grain ratios which these guys are using. For example, at a 2L/kg ratio, you would need strike water at around 77C to get a mash temp of 67ish, so the lower strike temps of 71 are for far different ratio's.

FYI I have found that a 2L/kg ratio works satisfactorally for a minimash, but you will get a more stable temperature if you use a thinner mash, ie more water, due to the larger thermal mass. Of course, it is also more difficult to adjust if you get it wrong.

Strike temp = (desired mash temp x (litres water x 0.4 x kg grain) - (0.4 x kg grain x malt temp)) / litres water

I hope that makes sense, just do the brackets first and you should be right.


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