I'm a pretty new AG brewer and haven't attempted any decoctions yet, but it's my understanding that (and I know I'm oversimplifying) a portion of the mash is taken out, boiled, and then returned to the main mash as an infusion.
When you take some of the mash for the decoction, do you scoop a bunch of "stuff" out of the tun or do you draw liquid out like you would at the sparge and just boil the fluid without any grains? Nothing I've read has really been clear on this for me.
I've been under the impression that boiling grains can release tanins and contribute to off flavors so I'd though the latter was true, but now I've also seen references to actually boiling some of the grist. Can anybody clear this up for me?