mash tun design problem - heat retention and insualtion.

[Midlife]

I preheat the tun first, then for the mash I wrap in the bed duvet and it only drops by about 1-2C over the 90 mins.

[Jim]

With a well insulated mash tun, heating the goods during the mash is simply not necessary.

If you want to do mashes with a variable temperature profile (e.g. to mimic a decoction mash) then you do need heating. For straightforward infusion mashes, no.

[clarets7]

I still think that given the small thermal mass you are going to have problems. How about putting the mash tun in a larger container full of water at the mash temperature, or slightly higher, and putting the insulation around that? It's all proportional.

[burrowsbrewery]

There are few ideas floating around in my head, a hot water jacket being one of them. I need to find the time this week to some more experiments.

I have neoprene, bubble wrap and water as insulation to play with as well comparing steel stock pots to plastic brew buckets. I also need to look at sealing where the lid meets the vessel. I have just had the idea of a neoprene coated vessel in a hot water jacket, like a wetsuit!

Looking at my calculations the best I have scored so far has been 0.414°C loss per minute, this equates to 3.73°C over 90 min. This was 4 litres of water in a 4.5 litre steel pot which was placed in a seven 7 litre steel pot. Itchy fibreglass loft insulation was packed between the two and a dressing gown covered the top.
The catch is all materials where thoroughly heated first and there were still a higher initial loss over in the first 20 minutes (which is not included in the figure). It’s an encouraging result though and the research will be useful for everyone else.

[burrowsbrewery]

Sorry for not following this up, I have had a lot going on.

I messed about with insulation for some time. Pre heating the vessel turned out to be very important but ultimately I was still losing 4 degC over 90 min. Nothing achieved the desired stable temperature or time & energy efficiency. I never did like the sound of the water jacket idea because I would need to heat the water but then I had a brainwave.

If I have a vessel in a vessel, the inner is the mash tun, the outer is the water jacket; I can use the water jacket for sparging, it’s almost at the right temp to begin with. The time and energy cost of heating the water jacket is neutralised because I need sparge water later anyway.

I tried the idea out on a brew 3 weeks ago. With the 4.5 litre pot in the 7 litre pot I had just enough room for the desired amount of jacket/sparge water; I placed this on the hob for temperature adjustment. My target was 68degC, I was able to hold this without adjusting too much. I can’t remember how many times I did but I was being very particular keeping it within 1degC and I didn’t find it too laborious. This was a vast improvement, the wort was a lot sweeter and stickier on the hands; the mash efficiency was greatly improved.

The only potential disadvantage is that if you’re not careful when adjusting the temp, the outer edge of the mash can become too hot; you have to move temperature probe to the edge when heating. I was very careful to make sure it only ever got to 71degC. After some rest time the mash equalised to the desired temp. I will the concept another try and record the facts.

I already have a new system design in my head. It’s a cylindrical stainless steel false bottom mash tun inside a larger stainless steel vessel. The outlet form the bottom of the mash tun passes thought the water jacket via a copper pipe terminating at a ball valve on the outer vessel. The outer vessel has its own ball valve for draining the jacket/sparge water; this could be done via an electric pump for sparging. The jacket/sparge water temperature could be electrically controlled. It’s a HLT and mash tun in one a bit like a Braumeister.

Ever heard of owt like it? Any thoughts?

[charliemartin]

Sounds like a very complex and expensive way just to maintain the mash temp. My first mash tun just used a foil lined camping mat wrapped round it and taped in place. To prevent heat loss to the head space I used a piece of Kingspan wall insulation cut to fit, wrapped in tin foil and clingfilm with a screw on top for easy removal. Camping mat came from Amazon and Kingspan from B & Q.

Cheers,
Charliemartin

[aamcle]

A little rummaging around on the bay turned up :- 191505175239 a 2 US gallon Igloo cooler. That's 7.6 litres about the right size and part of their top range is very good heat retention.

Aamcle

[alix101]

Obviously keeping the heat in such a small volume is difficult.
have you considered mashing for 20/30mins use an iodine test to confirm conversion. ..shorter brew day..win win.
also to you heat your mash tun with strike water and allow it to cool to your strike temp.

[burrowsbrewery]

I had seen the igloo cooler before, I thought it was very expensive for what it is at £40 and it might not work which is why I haven’t tried it. It would have to be VERY good insulation and the experiments I have done already show that 2 litres of airspace above a small mash adds to the problem.

Has anyone got one so seen one used elsewhere on the tinterwebs?

Stainless pots are very cheap and fabrication is not a problem for me, I consider it about the same expense as a standard 3 tier system because it’s still the same amount of vessels, taps and pipe work.

Another idea is effectively making my own thermos; air is actually a far superior insulator if it’s not allowed to move around creating convection. I could simply go vessel in a vessel at TIG weld a ring to make the void air tight. It’s also possible to create a partial vacuum by filling the void with steam during welding but that’s getting very fancy. The reason I’m not keen on this whole concept is because I can’t try it out before fabricating.

If it’s possible to shorten the mash by that much where does the 90min figure come from?

[alix101]

90 min mash time comes from tradition . I'm going to assume from a time when malt wasn't as good as modern malts and conversion took longer.
It's the age old debate of 60 or 90. ..well I'm certain with the quantity of grain your mashing your full conversion would be around 20mins at 65 /66 c.
even with a larger quantity I've seldom seen a standard pale based grist not convert by 30mins. ...
people say of you leave it longer you get a more fermentable wort I don't go along with that.

[burrowsbrewery]

After reading the results of the following link I’m definitely going to give short mash with iodine test a try on the next brew, this may lead to a rethink.

http://brulosophy.com/2014/09/01/does-m ... t-results/

[bigdave]

I use a plastic mango barrel wrapped in a hot water tank jacket (by wrapped I mean the jacket is duck taped on to it really well and covers the lid and base too). I used to get the most heat loss from around the top rim where the lid screws on, so started covering the mash tun with an old sleeping bag and now heat loss is usually less than 1ºC over a 60 min mash, even in the dead of winter. I also don't preheat my tun mainly because when I do, I completely overshoot my target strike and mash temps... on a side note, pre-heating your tun can help you hit strike temp or target mash temp but it isn't going to improve heat loss over the mash.

Something to bear in mind is that testing heat loss with just hot water is going to give you very different results to actually mashing (although you may well have noticed that by now). I could fill my mash tun with 66ºC water now and in 60 mins time I can almost guarantee it'd have lost at least 4ºC but add 4kg of grain and water at the same temp and it will hold it's temperature for that length.

If nothing else it sounds like you're having a real adventure with short brews! Good Luck

[alix101]

You should do a similar post to post your findings.
10 people will give you 10 answers for the same conclusion in brewing ...Best way to find out if it has an effect is to try it ...good luck. ..I'm sure you'll find that brew day becomes a lot shorter.

[bigdave]

I've seldom seen a standard pale based grist not convert by 30mins. ...

This is an interesting idea. do you know of any research being carried out as to where the cut off is for short mash vs volume of grain?

[Jim]

I think I might have said elsewhere that when I did the Black Sheep brewery tour, the guide said they mashed for 45 minutes. If it's good enough for them....

In Dave Line's original book, he described the mash reactions and his view was that while all the starch converts quite quickly, the dextrin to maltose ratio needs a bit more time to balance out. Personally, I've never had a problem with lack of wort fermentability - often had the reverse though, in the early days.