Mash tun temp...

[judasegg]

Hey,

Got myself a second-hand Coleman Coolbox (I think from late 90s, decent condition), converted to mash tun.

I think I'm missing something with temp measures people are reporting with mashtun, where they say they lose less than 1 degree...when I dough in, I see temp fluctuations in the range of a couple of degrees, depending where probe is.

After I eventually hit initial temp (say 66c), then even after 20 minutes I've lost a couple of degrees, but then I add hot water (from HLT - around 80c), and increased volume results in very little temp change overall, and lots of mixed readings (some spots read 77, others 63 - cooler than reading before addition and stirring)

I'm not sure how people are doing it, for 4.5kg grains I'm adding 13 litres of water, with 7 litres (at 80c) reserved for topping up temp.

I just feel like I'm doing LOTS of fiddling. I preheat mashtun with about 12 litres of boiling water, about 8-10 boils from my tea kettle. Grains are indoors, so should be relatively warm. I'm wondering if my thermometer is just too accurate (digital fancy one with probe), and people reporting less that one degree fluctuation are using less responsive ones...it probably takes me 20 minutes of stirring and testing just to hit, say 66.5c, then in 20 minutes its down to 64.3, add more water about every 15 minutes to keep it in recipe temp range.

I'm reluctant to replace coolbox mashtun (only second AG brew done), which would require making new manifold which was painful and expensive (that is, I can't justify spending £75-100 on some fancy Igloo cooler and copper and time for new manifold, especially when I hear about people using Tesco Value coolboxes for £9 and having no problems.

Ideally, I'd like to chuck the lid on and forget about it during the mash, not fret over the temp being all over the map...

Any ideas?

[jmc]

Hi judasegg

Which Coleman have you got? Any pics?

I must admit I was very dissapointed with heat loss I got on my Coleman coolbox mashtun.

I went a bit over the top with additional insulation,


Having said that it now works much better and only extra insulation I do is wrap bubblewrap around the tap, otherwise that acts as a heat sink.

I'd check yours is nicely warmed up before you add the grain and check its closed really well. (Maybe even strap it down)
Its amazing how much heat can be lost in the steam / water vapour if it can get out.

If its oversized you might want to try changing the ratio grain to water, i.e. add more mash water to have more thermal mass. And if you're still getting higher losses then you'll just need to add more insulation like blankets, camping mats etc. I also used to use hot water cyliner jacket insulation.

Currently I underlet as I think that helps as lid isn't opened for long.
Downside is its a bit more tricky to calc strike temp as you need to allow for extra temp to warm up mashtun.
(Mine is calculated strike temp plus 2.5C approx)

You'll see lots more info on this here if you search further.

See also:
Is bubble/foil insulation any good?
Mash Tun
etc

ATB John