Originally Posted by shetc
How do you fill the headspace?
I try to have a mash volume very close the volume of my kettle-tun. That's really the best way. Grist-water ratio is very flexible if you watch your pH, up to at least 1qt:1.5lbs.
I just got a 20 gal kettle I intend to use as a tun for 15 gal batches, and I am thinking it's going to be a little harder now since it's so big (though the larger liquid volume will buffer things some too). I kind of want to design a floating lid that sits over my mash, but I know that won't be happening immediately.