mash tun design problem - heat retention and insualtion.

[woblylegs]

if you doing a small mash in a stainless pan ive read that you can pop it in the oven set at its lowest possible setting and it will keep your temp. 1 or 2 gallon pot should fit in an oven no problem.

[alix101]

BYO did a wide spread experiment on mash times and starch conversion.
http://podbay.fm/show/75092679/e/1299024000?autostart=1
it's interesting worth a listen
the conclusion is you have conversion after 25/30 mins but a more fermentable wort after 60.
The trouble with the experiment to me is not every one used the same grain bill or and had variants on temperature.
I read somewhere that Bud is mashed for 5 hours to extract as much sugar as is possible Not surprising really.
There are to many variables to have a conclusive answer for how long to mash It will be variant on style also. But it's certainly worth experimenting with.
JBK group experiment

[burrowsbrewery]

If the mash time is not too long I hypothesise that there may be an ideal temperature range for the ‘outer jacket water’ that will maintain the average mash temp within 1degC without the need for heating. It’s a bit like having two strike temperatures.

I had figured about 45min may be a good compromise. I can understand why there is a debate on mash times less than 60min but I do wonder where 90min comes from; a lot of the American stuff I read says 60min. The irony is it’s the sort of question that this 1 gallon system is being designed to answer!

I've got some iodine, yeast and a few other things on the way. I will post the accurate details of the test method and the results when I brew next.

In response to other points:

Indeed water on its own looses heat faster that a mash but I did brew with one of the experimental insulation solutions and still found myself heating the mash; the difference didn’t negate the problem much.

I have a gas oven, gas mark 1 is 135°C so leaving the gas on is a no go. I have tried warming the oven first and using it as a hot box but it didn’t work very well at all, without the gas on it loses heat almost as faster than you’d think.

I had considered that a major point of heat loss is around the lid, I was thinking of adding clips and a foam gasket to the final design.

[burrowsbrewery]

The following is a short report on my 6th brew day 27/03/15.

Hypothesis: The use of a water jacket may keep the 1 gallon batch mash temperature within tolerance if the mash time is shorted to 45 minutes or less. There may be an ideal temperature range for the ‘outer jacket water’ that will maintain the average mash temp within 1degC without the need for heating.

Details:
Grist ratio 2.5 L/kg
Mash Liqour 3.3 L
Target OG 1.063
Target Volume 4.8 Litres
Assumed Efficiency 75%

Equipment:
7.657 L stainless steel pot as a water jacket, heated on a gas hob.
4.423 L stainless steel pot with flat lid as a mash tun.
Digital thermometer ( http://the-home-brew-shop.co.uk/acatalo ... Rbs1uFi5Yo )

Method:
1) Heat water to 80°C.
2) Add 3.3 L to mash tun, add 3.4 L to jacket (to the brim).
3) After doughing in, using the thermometer probe, measure the following immediately and at 15 minute intervals:
Water jacket – taken vertically, max probe depth.
Edge of mash – taken vertically, max probe depth.
Centre of mash - max probe depth at 45° angle form he edge.
Top of mash – taken from the centre
4) Carry out iodine test at 20 minutes then and then after each temperature check.
5) Heat the water jacket if the centre of mash drops below or is about to drop below 66°C or if it’s considered prudent to do so.

Results:
Target mash temp 68°C (+-0.5°C), strike temp for 68.5°C was calculated to be 75.3°C.
Note that once doughed in the mash was completly full; no air gap.
0 min (after doughing in)
Jacket: 69.7
Edge: 68.7
Centre: 66.6
Top: 66.3

At this point it is evident the target mash temp has not been reached, for the sake of the experiment it is now to be considered to be 66°C (-0.0°C +0.5°C).

15 min
Jacket: 65
Edge: 67.5
Centre: 66.1
Top: 65.8

20 min Iodine test: black/purple

30 min
Jacket: 61.5
Edge: 65.8
Centre: 66.4
Top: 65.0
Iodine test: black/purple

45 min
Jacket: 57.7
Edge: 62.2
Centre: 66.1
Top: 61.6
Iodine test: black/purple

Jacket heated, heating stopped at 52 min.
Jacket: 75

60min
Jacket: 71.2
Edge: 69.1
Centre: 66.4
Top: 62.2
Iodine test: Brown

75 min
Jacket: 65
Edge: 66.9
Centre: 64.9
Top: 61.3
Iodine test: reddish brown at first, turned black with yellow.

Aware that I may not be converting starches due to temperature loss I decide to heat the jacket, heating stopped at 88 min.
Jacket: 75

90 min
Jacket: 70.9
Edge: 68.3
Centre: 66
Top: 60.3
Iodine test: reddish brown then grey

END OF MASH

Sparge:
3.4 L of sparge water heated to 85°C
Average temp of grain bed halfway through: 75°C
Average temp of grain bed after sparging: 65°C
Iodine test: dark & murky yellow
Pre boil Gravity: 1.0449
Wort collected: 5.47 L
Mash efficiency: 63.2 %

my target OG was not reached after 90 min boil; 1.609.

Conclusion:
A water jacket could keep the mash at the desirable temperature IF it was heated regularly or constantly with a controller.
Starting the jacket at a higher temperature would likely heat the mash excessively.
I assume efficiency was probably poor due all but the centre dropping below 66°C at various points; this would explain the poor iodine test results.
It is inconclusive as to weather a shorter mash in this instance is possible.

Comments:
Starting to think maybe I should have done some extract brewing before to perfect various other things before trying to mash, but then again I like a challenge. Also thought maybe I should give up and scale up to 5 gallon; all tolerance issues sound lessened in larger batches.
Then again the results do show some promise, with an electronic control (and maybe a larger jacket) the concept should keep the centre of the mash at a very constant temperature with to outer edge being ~2°C higher, perhaps less. This would be a viable design as long as a suitable heating element could be procured.
The complexity is increased somewhat but no wear near as much as RIMS or HERMS. In some ways it’s a bit like HERMS without the recirculation pump; call it HEMS?

[aamcle]

There is an easy way, instead of trying to produce a MT that has very little or no heat loss recirculate heated wort through the grain bed.
A RIMS or HERMS, recirculating BIAB, GrainFather or small BM type should do what you need.
Or if you don't fancy that type a thermostatically controlled oven/heated box to put your MT in.

Good Luck. Aamcle

[Ren]

I believe Recirculating BIAB is a way to go. That's why i bought a pump and a biab bag and pid controller. will do my first ebiab brew next week. I have igloo industrial mash tun 5 gal with insulated lid and when I made 10 litre batches temperature losses where significant compared to 5 gal batch brews.

[aamcle]

Ren.

If you find that the flow when balanced is low and you may a basket that holds the bag off the walls of the boiler should sort you out.

Good Luck. Aamcle

[Ren]

Ren.

If you find that the flow when balanced is low and you may a basket that holds the bag off the walls of the boiler should sort you out.

image.jpg

Good Luck. Aamcle

Where did you get it from? I was actually considering basket but wanted to try without one first

[aamcle]

I made that from the remains of a perforated Burco and some SS mesh. If you look at commercial recirculating biab systems most if not all use some sort of basket, its very hard to get good flow without one.


Atb. Aamcle

[Ren]

I made that from the remains of a perforated Burco and some SS mesh. If you look at commercial recirculating biab systems most if not all use some sort of basket, its very hard to get good flow without one.


Atb. Aamcle

I just did a test with some old grains and it was flawless without basket. It's ok for 10l batches i guess and I use buffalo boiler which has large diameter so grain bed is quite thin.