[shpxnvz]

The mash temperature needs to be pretty exact, and I (personally) find it hard to do fine temperature control with a burner. Even a few degrees variation during mash can favor different enzymes and result in inconsistent starch conversion or an alteration in flavor. I've never had much success trying to keep the temperature that steady for a full hour using a propane burner. That's not to say no-one else has success that way.

Besides that, I use a big 100 quart cooler as a mash tun to help keep the temp consistent which precludes using external heat.

A little background info on mashing for those interested: http://www.byo.com/stories/techniques/article/indices/45-mas...

[WiseWeasel]

My roommate was just using a burner and a pot to heat the water to the desired temp, and then he placed the hot water in a big insulated cooler, which keeps the temperature extremely stable for the hour or so while the warm water flows down into the sparging system in a second cooler holding the mash, unless I'm just completely confused about the process...

[shpxnvz]

Yeah, if you have a cooler that consistent and adjust your temp for the measured thermal mass of the cooler it would work fine. Mine loses about ten degrees per hour at mash temp, however, so I need to adjust the temp pretty continuously during mash.

Of course, another part of it is just my desire to hack together nifty gadgets. :-)