Feeling hot, hot, hot… a fascinating post on insulating a pot

BIAB#1 went almost worryingly well. It looked like stout, the airlock bubbled and, two weeks on, has fermented down to 1010.  Result!  A quick taste while bottling also suggests we’re on to something that’s a big step up in quality from the kits we’d been brewing previously.  No ‘twang’, clean tasting, really promising.

So far, so positive.  There’s no way we’re going to start getting complacent after just one brew, though.  Oh, no!  The big issue from the first brewday was that the pan we’re using as a mash tun has no insulation and our attempt to counter this by wrapping it up in a blanket wasn’t nearly good enough.

So, alongside planning our next brew (which will be a lager, by the way), our thoughts turned to how best to insulate the pan.  Jono sourced aluminium radiator reflector foil, some heat resistant tape and we were ready to go.


Like wrapping presents for Christmas all over again

We taped a totally arbitrary 3 layers of foil to the outside of the pan.  It didn’t look so pretty anymore, but it was still shiny so that’s something.


Pan bundled up to keep it nice and warm. Hopefully.

As we are nobody’s fools, we also remembered to make the pan a decent hat to go along with it’s nice, new, cosy jacket.  This was, again, 3 layers of foil which we reinforced with cardboard.


One insulated pan lid.

Following a good half an hour’s work, we had our finished product and were ready to wrap it back up in the blanket and put it through its paces.


One pot, insulated to make it a more effective mash tun.

The delight we had in our efforts was soon crushed, though.  7 litres of 72C water lost 10 degrees across an hour. This was a slight improvement on previously, but nothing like as much as hoped.  Devastating!

Rather than tear all the foil off and rush back to the drawing board, we’ll push ahead with the new look pan for the next brew.  The hope is that when the grain bags are in and the pan is full – with dead headspace reduced – the rate of heat loss will improve.  We’ll get it next to a radiator and, if necessary, we can just top up with some boiling water (thanks @FourStringDave).  Hopefully all that will mean we can hold a decent high mash temperature.

If we come up with a better solution, then we’ll post that here.  Any suggestions for other things we could try would be great too.

Next brew (lager) should be going on Saturday, 15th February.


4 thoughts on “Feeling hot, hot, hot… a fascinating post on insulating a pot

  1. Ian Darvill (@Lugsy51)

    Do you stand the pan on an insulated base too? I found this helped massively when I did BIAB, just fold up a couple of towels and stand the pot on that. Then I used to wrap it with more towels and secure in place with bungee cords, finally adding a sleeping bag and a duvet to be sure. I still used to lose 5 degrees or so over a 90 minute mash in the winter but it served me well before I went multi-vessel.


    1. bagboilbeer Post author

      Hi Ian

      Thanks for that. I feel a bit dim admitting it, but I hadn’t thought about extra insulation for the base too. I imagine that would make quite a difference, so will do that next time. Cheers.

      Just as you mentioned it, and it’s the second time Ive heard it suggested for BIAB, would you recommend a 90 minute mash over a 60?

      Thanks again for the advice.



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