This is how i reduced my headspace in my masttun

[wilserbrewer]

I use a 10 gal igloo preheat for 20 min the add grain and a 2" styrofoam lid the the cooler lid and still lose 3-4 degrees. I also add the grain 2 degrees hotter and stir the piss out of it till my arm is dead and usually close it up 1 degree hotter than the target. What am I doing wrong. My grain to water ratio is 1.30

my guess would be that you are not preheating adequately, or you are not wating long enough for the grain water temp to stabilize...the mash temp will drop for about 5 minutes till it becomes constant...checking it too soon will indicate false highs IMO.

 

[HangLoose]

I use a 10 gal igloo preheat for 20 min the add grain and a 2" styrofoam lid the the cooler lid and still lose 3-4 degrees. I also add the grain 2 degrees hotter and stir the piss out of it till my arm is dead and usually close it up 1 degree hotter than the target. What am I doing wrong. My grain to water ratio is 1.30

Are you taking the starting temperature of your grain into account?

 

[tre9er]

This is why I heat strike to 180 and pre-heat my tun with it. I leave it in there for a good 10 minutes then stir down to just ABOVE prescribed strike temp from software and dough-in a little high. I stir like crazy and then once I'm in the upper range of my mash temp, cover it up and throw a blanket on it.

 

[ekjohns]

This is why I heat strike to 180 and pre-heat my tun with it. I leave it in there for a good 10 minutes then stir down to just ABOVE prescribed strike temp from software and dough-in a little high. I stir like crazy and then once I'm in the upper range of my mash temp, cover it up and throw a blanket on it.

this is exactly what I do, only I preheat for 20 min and still loose 4 degrees over 1 hr. usually with about 11 lbs of grain

 

[tre9er]

this is exactly what I do, only I preheat for 20 min and still loose 4 degrees over 1 hr. usually with about 11 lbs of grain

Weird. I lose about a degree, if that. I've always liked the way this cooler held temps even though it's not fancy or expensive. It's a rectangular 7g. cooler, maybe an igloo or coleman...not sure.

 

[Rundownhouse]

I've tried a couple 5gal/~12lb grain batches in my 25g mash tun and it loses heat at a crazy pace compared to when I've got a 10gal/~25lb grain batch in there.