Mash Tun Temp control

[Brew107]

Hi, yes I'm a new member to this forum but i've been brewing beer and wine for a long time, yep half a century!!! Anyway enough of that, I'd like to share what little I know. So when my mash tun needed replacing I thought I would go "bigger is best" and got a 40+ltr unit ( I generally brew 23 ltr at a time), this however gave me a problem, I found that I couldn't maintain the temp of the mash and would regularly see a fall of up to 10 deg C on the initial mash(I use a digital thermometer in the tun)thus correcting continually. I concluded that I had too much head space to heat, solution!! cut down the excess head space, simple ?? The tun has a screw top so I couldn't cut the tun down, so I solved the problem by cutting a 2inch "Kingspan" insulation board into a circle which I place into a small peddle bin liner and lower onto the mash and replace the tun lid. Remember the digital thermometer? Well I can now hold the mash temp within 1 deg C for the complete process. I then reuse the bin liner to dispose of the grains after the sparging. ( ah sanitising, no problem there as the wart is to be boiled After the use for the mash tun) and I haven't had any issues todate. I hope this helps anyone out there who has been suffering with a similar problem. Happy brewing.